K.B. acknowledges funding from the fellowship program of the German National Academy of Sciences Leopoldina, grant LPDS 2016-06 and the European Space Agency. Furthermore, she would like to thank Dr. Leopold Summerer, the Advanced Concepts Team, Alan Dowson, Dr. Jack van Loon, Dr. Gabor Milassin and Dr. Robert Lindner (ESTEC), Robbert-Jan Noordam (Notese) and Prof. Harry B. Gray (Caltech) for their great support. M.H.R. is grateful for generous support from Prof. Nathan S. Lewis (Caltech). K.B. and M.H.R. acknowledge support from the Beckman Institute of the California Institute of Technology and the Molecular Materials Research Center. The PhotoEChem Team greatly acknowledges funding from the German Aerospace Center (Deutsches Zentrum f&#252;r Luft- und Raumfahrt e.V.) for the project no. 50WM1848. Furthermore, M.G. acknowledges funding from the Guangdong Innovative and Entrepreneurial Team Program titled &#34;Plasmonic Nanomaterials and Quantum Dots for Light Management in Optoelectronic Devices&#34; (no. 2016ZT06C517). Furthermore, the author team greatly acknowledges the effort and support from the ZARM Team with Dieter Bischoff, Torsten Lutz, Matthias Meyer, Fred Oetken, Jan Siemers, Dr. Martin Castillo, Magdalena Thode and Dr. Thorben K&#246;nemann. It is also thankful for enlightening discussions with Prof. Yasuhiro Fukunaka (Waseda University), Prof. Hisayoshi Matsushima (Hokkaido University) and Dr. Slobodan Mitrovic (Lam Research).

1. Preparation of p-InP photoelectrodes
<ol>
	<li>Use single crystal p-InP (orientation (111 A), Zn doping concentration of 5 &#215; 1017 cm-3) as the photoabsorber. For the back contact preparation, evaporate 4 nm Au, 80 nm Zn and 150 nm Au on the backside of the wafer and heat it to 400 &#176;C for 60 s.</li>
	<li>Apply Ag paste to attach the ohmic contact to a thin-plated Cu wire. Thread the wire to a glass tube, encapsulate the sample and seal it to the glass tube using black, chemical resistant epoxy.</li>
	<li>In order to remove native oxides, etch the 0.5 cm2 polished indium face of p-InP for 30 s in 10 mL of bromine/methanol solution (0.05 % w/v), rinse the surface with ethanol and ultrapure water for 10 s each and dry the sample under nitrogen flux. Prepare the solutions from ultrapure water and analytical grade chemicals with an organic impurity level below 50 ppb. 
	CAUTION: Bromine causes acute toxicity upon inhalation, skin corrosion and acute aquatic toxicity. Wear protective equipment such as safety glasses, gloves and lab coat. Work under the fume hood. Methanol is flammable, causes acute toxicity (oral, dermal and inhalation) and is known to cause specific target organ toxicity. Wear protective equipment such as safety glasses, gloves and a lab coat. Work under the fume hood.</li>
	<li>Subsequently, condition the p-InP electrode photoelectrochemically in a standard three-electrode potentiostatic arrangement. Use a borosilicate glass cell with a quartz window as a photoelectrochemical cell in order to illuminate the sample with a white-light tungsten halogen lamp (100 mW/cm2) during the procedure.</li>
	<li>Adjust the light intensity with a calibrated silicon reference photodiode.</li>
	<li>Prepare a 0.5 M HCl solution and purge it in the photoelectrochemical cell with nitrogen of 5.0 purity for 15 min.</li>
	<li>Use potentiodynamic cycling between -0.44 V und +0.31 V at a scan rate of 50 mV s-1 for 50 cycles to photoelectrochemically condition the sample under continuous illumination. 
	CAUTION: Hydrochloric acid causes serious eye damage, skin corrosion and it is corrosive to metals. Furthermore, it possesses specific target organ toxicity following single exposure. Wear protective equipment such as safety glasses, gloves and a lab coat. Work under the fume hood.</li>
</ol>
2. Fabrication of rhodium nanostructures
<ol>
	<li>Employ shadow nanosphere lithography (SNL)11,12 for the formation of rhodium nanostructures on the p-InP photoelectrode. In order to create the polystyrene masks on the p-InP electrode, obtain mono-dispersed beads of polystyrene (PS) sized 784 nm at a concentration of 5% (w/v) and dissolve them in ultrapure water.</li>
	<li>To obtain the final volume of 600 &#956;L, mix 300 &#956;L of the polystyrene bead dispersion with 300 &#956;L of ethanol containing 1% (w/v) styrene and 0.1% sulphuric acid (v/v).</li>
	<li>Apply the solution onto the water surface using a Pasteur pipette with a curved tip. In order to increase the area of the monocrystalline structures, turn the Petri dish gently. Carefully distribute the solution to cover 50% of the air-water interface with a hcp monolayer. Leave place for stress relaxation and avoid forming cracks in the lattice during the next preparation steps.</li>
	<li>Protect the Cu wire of the photoelectrochemically conditioned p-InP electrodes with parafilm. Place them delicately under the floating closed packed PS sphere mask by carefully taping them to a microscope slide, preventing the samples from rotating. Gently remove residual water with a pipette and by evaporation, causing the mask to be subsequently deposited onto the electrode surface.</li>
	<li>Take the electrode out of the Petri dish and gently dry the surface with N2. Store the electrode under nitrogen until rhodium photoelectrodeposition (e.g., in a desiccator). 
	NOTE: The protocol can be paused here for up to one week.</li>
</ol>
3. Photoelectrodeposition of rhodium nanoparticles
<ol>
	<li>For the photoelectrochemical deposit of rhodium nanoparticles through the PS sphere mask, place the electrode in an electrolyte solution containing 5 mM RhCl3, 0.5 M NaCl and 0.5% (v/v) 2-propanol and apply a constant potential of Vdep = +0.01 V for 5 s under simultaneous illumination with a W-I lamp (100 mW/cm2). Electrochemical specifications such as the electrochemical cell, reference and counter electrode are the same as for the photoelectrochemical conditioning procedure.</li>
	<li>Rinse the photoelectrode with ultrapure water and dry it under a gentle flow of N2.</li>
	<li>In order to remove the PS-spheres from the electrode surface, place the electrodes for 20 min under gentle stirring in a beaker with 10 mL of toluene (the electrode should be covered with toluene). Subsequently, rinse the electrode with acetone and ethanol for 20 s each.</li>
	<li>Remove residual carbon from the surface by O2-plasma cleaning for 6 min at a process pressure of 0.16 mbar, 65 W and gas inflows of O2 and Ar of 2 sccm and 1 sccm, respectively.</li>
	<li>Prepare the samples up to one week prior to tests in the drop tower and store them until the experiments under N2 atmosphere in the dark (e.g., in a glove bag or desiccator). 
	NOTE: The protocol can be paused here for about 1-2 weeks.</li>
</ol>
4. Photoelectrochemical experiments in microgravity
<ol>
	<li>For the experiments in microgravity environment, contact one of the major drop tower facilities, (e.g., the Centre of Applied Space Technology and Microgravity (ZARM), Bremen Germany). 
	NOTE: By employing a catapult system, 9.3 s of microgravity environment can be generated at ZARM with an approached minimum g-level of about 10-6 m&#183;s-2 13. A hydraulically controlled pneumatic piston-cylinder system is used to launch the drop capsule (Figure 1A) upwards from the bottom of the tower. The capsule is decelerated again in a container which is placed onto the cylinder system during the time of free fall.</li>
	<li>Use a two-compartment photoelectrochemical cell (filling volume of each cell: 250 mL) for the photoelectrochemical experiments in order to carry out two experiments in microgravity environment in parallel. The front of each cell should consist of an optical quartz glass window (diameter: 16 mm) for illuminating the working electrode (see Figure 1B).</li>
	<li>Employ a three-electrode arrangement in each cell for the photoelectrochemical measurements with a Pt counter electrode and an Ag/AgCl (3 M KCl) reference electrode in HClO4 (1 M). Add 1% (v/v) isopropanol to the electrolyte in order to reduce the surface tension and enhance gas bubble release. Use a W-I white light source for illuminating each cell compartment through the optical windows. 
	CAUTION: Concentrated perchloric acid is a strong oxidizer. Organic, metallic and non-organic salts formed from oxidation are shock sensitive and pose a great fire and explosion hazard. Wear safety glasses, gloves and a protective lab coat. Work under the fume hood and minimize bench top storage time.</li>
	<li>For gas bubble investigations, attach two cameras to each cell via optical mirrors and beamsplitters (e.g., a color camera at the front and a monochromatic camera at the side, see Figure 1) to record gas bubble evolution during free fall of the experiment. For each drop, store the recorded data on an integrated board computer in the drop capsule. Record single pictures at a frame rate of (e.g., 25 fps (color camera) and 60 fps (monochromatic camera)).</li>
	<li>The drop capsule is equipped with several boards (Figure 1). Mount the photoelectrochemical set-up and the cameras onto an optical board and attach it to one of the middle boards in the capsule. Use the remaining boards for installment of additional equipment such as potentiostats, light sources, shutter controls and the board computer. Attach a battery supply at the bottom board of the capsule to power the set-up during free fall (Figure 1).</li>
	<li>Write an automated drop sequence for the experimental steps which should be controlled and carried out in microgravity environment. The program should be started prior to each drop. Upon reaching microgravity environment, the sequence should automatically start cameras, illumination sources and the electrochemical experiment for the duration of 9.3 s while simultaneously immersing the working electrode into the electrolyte using a pneumatic system (see Figure 1, Table 1).</li>
	<li>Investigation of light-assisted hydrogen production on the samples in photoelectrochemical measurements (e.g., cyclic voltammetry and chronoamperometry).
	<ol>
		<li>Control the electrochemical parameters by the two potentiostats in the capsule. For optimal resolutions in J - V measurements, use scan rates (dE/dt) of 218 mV/s to 235 mV/s in order to run 3 scan cycles in cycling voltammetry experiments, using voltage ranges of +0.25 V to -0.3 V vs Ag/AgCl (3 M KCl). Employ the initial potential, Ei = +0.2 V vs Ag/AgCl (3 M KCl) and the finishing potential, Ef = +0.2 V vs Ag/AgCl (3 M KCl). To compare the recorded J - V measurements, take the second scan cycle of each experiment for analysis.</li>
		<li>In chronoamperometric measurements, use the time scale of generated microgravity environment, 9.3 s, to record the photocurrent produced by the sample. Apply potential ranges of -0.3 V to -0.6 V vs Ag/AgCl (3 M KCl) to compare produced photocurrents.</li>
	</ol>
	</li>
	<li>At the end of each drop, when the drop capsule is decelerated again to zero velocity, use the drop sequence to let the sample be removed from the electrolyte and cameras, potentiostats and illumination sources be switched off.</li>
	<li>After retrieving the capsule from the deceleration container, remove the capsule protection shield. Remove the samples from the pneumatic stative, rinse them with ultrapure water and dry them under gentle nitrogen flux. Store them under N2 atmosphere until optical and spectroscopic investigations are carried out.</li>
	<li>Exchange the electrolyte in the two cells, ensure the function of all instruments before equipping the cells with new samples and prepare the capsule for another drop experiment.</li>
</ol>

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The authors have nothing to disclose.

For the preparation of photoelectrodes, it is important to minimize oxygen exposure between the etching and conditioning procedure and to purge the 0.5 M HCl before usage for about 10 - 15 min with nitrogen. Once the samples are conditioned, they can be stored under nitrogen atmosphere in 15 mL conical tubes for a few hours to allow sample transport and/ or preparation time of the polystyrene particle masks. In order to achieve a homogenous arrangement of PS spheres on the electrode substrate, it is important to form a c...

Our atmosphere on Earth is formed through oxygenic photosynthesis, a 2.3-billion-year-old process converting solar energy into energy-rich hydrocarbons, releasing oxygen as a by-product and using water and CO2 as substrates. Currently, artificial photosynthetic systems following the concept of the energetic Z-scheme of catalysis and charge transfer in natural photosynthesis are realized in semiconductor-electrocatalyst systems, showing hitherto a solar-to-hydrogen conversion efficiency of 19 %1,2,3. In these systems, semiconductor materials are employed as light absorbers which are coated with a thin, transparent layer of electrocatalysts4. Intense research in this field is promoted by the global quest for renewable energy systems with hydrogen and long-chain hydrocarbons making excellent candidates for an alternative fuel supply. Similar obstacles are also faced on long-term space missions, where a resupply of resources from Earth is not possible. A reliable life-support hardware is required, employing an efficient air revitalization unit providing about 310 kg of oxygen per crew member per year, not accounting for extravehicular activities5. An efficient solar water-splitting device, capable of producing oxygen and hydrogen or reduce carbon dioxide solar-assisted and in a monolithic system would provide an alternative, lighter route to currently employed technologies on the ISS: the air revitalization unit is comprised of a separated system with an alkaline electrolyzer, a solid amine carbon dioxide concentrator and a Sabatier reactor for the reduction of CO2.
Unprecedentedly, we realized efficient solar-hydrogen production in microgravity environment, provided by a 9.3 s during free-fall at the Bremen Drop Tower (ZARM, Germany)6. Using p-type indium phosphide as a semiconducting light-absorber7,8 coated with a nanostructured rhodium electrocatalyst, we overcame substrate and product mass transfer limitations to and from the photoelectrode surface, which is an obstacle in reduced gravity environments due to the absence of buoyancy9,10. The application of shadow nanosphere lithography11,12 directly on the photoelectrode surface allowed the formation of rhodium catalytic 'hot spots', which prevented hydrogen gas bubble coalescence and the formation of a froth layer in proximity of the electrode surface.
Herein, we provide experimental details of the p-InP photoelectrode preparation including surface etching and conditioning, followed by the application of shadow nanosphere lithography on the electrode surface and the photoelectrodeposition of rhodium nanoparticles through the polystyrene spheres. Furthermore, the experimental set-up in the drop capsule at the Bremen Drop Tower is described and details of the experimental sequence during the 9.3 s of free fall are provided. Sample installment and handling before and after each drop are outlined as well as the preparation of the drop capsule and its equipment to operate illumination sources, potentiostats, shutter controls and video cameras upon command.

<table border="1" fo:keep-together.within-page="1" fo:keep-with-next.within-page="always">
	<tbody>
		<tr>
			<td>12.7 mm XZ Dovetail Translation Stage with Baseplate, M4 Taps (4 x)</td>
			<td>Thorlabs</td>
			<td>DT12XZ/M</td>
			<td></td>
		</tr>
		<tr>
			<td>Beam splitters (2 x)</td>
			<td>Thorlabs</td>
			<td>CM1-BS013</td>
			<td>50:50 400-700nm</td>
		</tr>
		<tr>
			<td>Beamsplitters (2 x)</td>
			<td>Thorlabs</td>
			<td>CM1-BS014</td>
			<td>50:50 700-1100nm</td>
		</tr>
		<tr>
			<td>Ohmic back contact: 4 nm Au, 80 nm Zn, 150 nm Au</td>
			<td>Out e.V., Berlin, Germany</td>
			<td>https://www.out-ev.de/english/index.html</td>
			<td>Company provides custom made ohmic back contacts</td>
		</tr>
		<tr>
			<td>Glass tube, ca. 10 cm, inner diameter about 4 mm</td>
			<td>E.g., Ga&#223;ner Glasstechnik</td>
			<td></td>
			<td>Custom made</td>
		</tr>
		<tr>
			<td>p-InP wafers, orientation 111A, Zn doping concentration: 5 x 10^17 cm^-3</td>
			<td>AXT Inc. Geo Semiconductor Ltd. Switzerland</td>
			<td></td>
			<td>Custom made</td>
		</tr>
		<tr>
			<td>Photoelectrochemical cell for terrestrial experiments</td>
			<td>E.g., glass/ materials workshop</td>
			<td></td>
			<td>Custom made</td>
		</tr>
		<tr>
			<td>Matrox 4Sight GPm (board computer)</td>
			<td>Matrox imaging</td>
			<td></td>
			<td>Ivy Bridge, 7 x Cable Ace power I/O HRS 6p, open 10m, Power Adapter for Matrox 4sight GPm, Samsung 850 Pro 2,5&#34; 1 TB, Solid State Drive in exchange for the 250Gb hard drive</td>
		</tr>
		<tr>
			<td>2-propanol</td>
			<td>Sigma Aldrich</td>
			<td>I9516-500ML</td>
			<td></td>
		</tr>
		<tr>
			<td>35mm Kowa LM35HC 1&#34; Sensor F1.4 C-mount (2 x)</td>
			<td>Basler AG</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Acetone</td>
			<td>Sigma Aldrich</td>
			<td>650501-1L</td>
			<td></td>
		</tr>
		<tr>
			<td>Ag/AgCl (3 M KCl) reference electrode</td>
			<td>WPI</td>
			<td>DRIREF-5</td>
			<td></td>
		</tr>
		<tr>
			<td>Aluminium breadboard, 450 mm x 450 mm x 12.7mm, M6 Taps (2 x)</td>
			<td>Thorlabs</td>
			<td>MB4545/M</td>
			<td></td>
		</tr>
		<tr>
			<td>Beaker, 100 mL</td>
			<td>VWR</td>
			<td>10754-948</td>
			<td></td>
		</tr>
		<tr>
			<td>Black epoxy</td>
			<td>Electrolube</td>
			<td>ER2162</td>
			<td></td>
		</tr>
		<tr>
			<td>Bromine</td>
			<td>Sigma Aldrich</td>
			<td>1.01945 EMD Millipore</td>
			<td></td>
		</tr>
		<tr>
			<td>Colour camera (2 x)</td>
			<td>Basler AG</td>
			<td>acA2040-25gc</td>
			<td></td>
		</tr>
		<tr>
			<td>Conductive silver epoxy</td>
			<td>MG Chemicals</td>
			<td>8331-14G</td>
			<td></td>
		</tr>
		<tr>
			<td>Copper wire</td>
			<td>E.g., Sigma Aldrich</td>
			<td>349224-150CM</td>
			<td></td>
		</tr>
		<tr>
			<td>Ethanol</td>
			<td>Sigma Aldrich</td>
			<td>459844-500ML</td>
			<td></td>
		</tr>
		<tr>
			<td>Falcon tubes, 15 mL</td>
			<td>VWR</td>
			<td>62406-200</td>
			<td></td>
		</tr>
		<tr>
			<td>Glove bags</td>
			<td>Sigma Aldrich</td>
			<td>Z530212</td>
			<td></td>
		</tr>
		<tr>
			<td>Hydrochloric acid (1 M)</td>
			<td>Sigma Aldrich</td>
			<td>H9892</td>
			<td></td>
		</tr>
		<tr>
			<td>Magnetic stirrer</td>
			<td>VWR</td>
			<td>97042-626</td>
			<td></td>
		</tr>
		<tr>
			<td>Methanol</td>
			<td>Sigma Aldrich</td>
			<td>34860-100ML-R</td>
			<td></td>
		</tr>
		<tr>
			<td>Microscope slides</td>
			<td>VWR</td>
			<td>82003-414</td>
			<td></td>
		</tr>
		<tr>
			<td>MilliQ water</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>NIR camera (2 x)</td>
			<td>Basler AG</td>
			<td>acA1300-60gm</td>
			<td></td>
		</tr>
		<tr>
			<td>Nitrogen, grade 5N</td>
			<td>Airgas</td>
			<td>NI UHP300</td>
			<td></td>
		</tr>
		<tr>
			<td>&#216; 1&#34; Stackable Lens Tubes (6 x)</td>
			<td>Thorlabs</td>
			<td>SM1L03</td>
			<td></td>
		</tr>
		<tr>
			<td>O2 Plasma Facility</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>OEM Flange to SM Thread Adapters (4 x)</td>
			<td>Thorlabs</td>
			<td>SM1F2</td>
			<td></td>
		</tr>
		<tr>
			<td>Parafilm</td>
			<td>VWR</td>
			<td>52858-000</td>
			<td></td>
		</tr>
		<tr>
			<td>Pasteur pipette</td>
			<td>VWR</td>
			<td>14672-380</td>
			<td></td>
		</tr>
		<tr>
			<td>Perchloric acid (1 M)</td>
			<td>Sigma Aldrich</td>
			<td>311421-50ML</td>
			<td></td>
		</tr>
		<tr>
			<td>Petri dish</td>
			<td>VWR</td>
			<td>75845-546</td>
			<td></td>
		</tr>
		<tr>
			<td>Photoelectrochemical cell for microgravity experiments</td>
			<td>E.g., glass/ materials workshop</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Polystyrene particles, 784 nm, 5 % (w/v)</td>
			<td>Microparticles GmbH</td>
			<td>0.1-0.99 &#181;m size (50 mg/ml): 10 ml, 15 ml, 50 ml</td>
			<td></td>
		</tr>
		<tr>
			<td>Potentiostats (2 x)</td>
			<td>Biologic</td>
			<td>SP-200/300</td>
			<td></td>
		</tr>
		<tr>
			<td>Pt counter electrode</td>
			<td>ALS-Japan</td>
			<td>12961</td>
			<td></td>
		</tr>
		<tr>
			<td>Rhodium (III) chlorid</td>
			<td>Sigma Aldrich</td>
			<td>520772-1G</td>
			<td></td>
		</tr>
		<tr>
			<td>Shutter control system (2 x)</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Silicon reference photodiode</td>
			<td>Thorlabs</td>
			<td>FDS1010</td>
			<td></td>
		</tr>
		<tr>
			<td>Sodium chlorid</td>
			<td>Sigma Aldrich</td>
			<td>567440-500GM</td>
			<td></td>
		</tr>
		<tr>
			<td>Stands and rods to fix the cameras</td>
			<td>VWR</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Sulphuric acid (0.5 M)</td>
			<td>Sigma Aldrich</td>
			<td>339741-100ML</td>
			<td></td>
		</tr>
		<tr>
			<td>Telecentric High Resolution Type WD110 series Type MML1-HR110</td>
			<td>Basler AG</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Toluene</td>
			<td>Sigma Aldrich</td>
			<td>244511-100ML</td>
			<td></td>
		</tr>
		<tr>
			<td>Various spare beakers and containers for leftover perchloric acid etc for the drop tower</td>
			<td>VWR</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>W-I lamp with light guides (2 x)</td>
			<td>Edmund Optics</td>
			<td>Dolan-Jenner MI-150 Fiber Optic Illuminator</td>
			<td></td>
		</tr>
		<tr>
			<td>CM-12 electron microscope with a twin objective lens, CCD camera (Gatan) system and an energy dispersive spectroscopy of X- rays (EDS) system)</td>
			<td>Philips</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Dimension Icon AFM, rotated symmetric ScanAsyst-Air tips (silicon nitride), nominal tip radius of 2 nm</td>
			<td>Bruker</td>
			<td></td>
			<td></td>
		</tr>
	</tbody>
</table>

experimental methods for efficient solar hydrogen production in microgravity environment

Long-term space flights and cis-lunar research platforms require a sustainable and light life-support hardware which can be reliably employed outside the Earth's atmosphere. So-called 'solar fuel' devices, currently developed for terrestrial applications in the quest for realizing a sustainable energy economy on Earth, provide promising alternative systems to existing air-revitalization units employed on the International Space Station (ISS) through photoelectrochemical water-splitting and hydrogen production. One obstacle for water (photo-) electrolysis in reduced gravity environments is the absence of buoyancy and the consequential, hindered gas bubble release from the electrode surface. This causes the formation of gas bubble froth layers in proximity to the electrode surface, leading to an increase in ohmic resistance and cell-efficiency loss due to reduced mass transfer of substrates and products to and from the electrode. Recently, we have demonstrated efficient solar hydrogen production in microgravity environment, using an integrated semiconductor-electrocatalyst system with p-type indium phosphide as the light-absorber and a rhodium electrocatalyst. By nanostructuring the electrocatalyst using shadow nanosphere lithography and thereby creating catalytic 'hot spots' on the photoelectrode surface, we could overcome gas bubble coalescence and mass transfer limitations and demonstrated efficient hydrogen production at high current densities in reduced gravitation. Here, the experimental details are described for the preparations of these nanostructured devices and further on, the procedure for their testing in microgravity environment, realized at the Bremen Drop Tower during 9.3 s of free fall.

Etching the p-InP surface in Br2/ methanol for 30 s with consecutive photoelectrochemical conditioning of the sample by cycling polarization in HCl is well established in the literature and discussed (e.g., by Schulte &#38; Lewerenz (2001)14,15). The etching procedure removes the native oxide remaining on the surface (Figure 2) and electrochemical cycling in HCl causes furthermore a conside...

Watch this Scientific Journal Video about Experimental Methods for Efficient Solar Hydrogen Production in Microgravity Environment at JoVE.com

Experimental Methods for Efficient Solar Hydrogen Production in Microgravity Environment

Efficient solar-hydrogen production has recently been realized on functionalized semiconductor-electrocatalyst systems in a photoelectrochemical half-cell in microgravity environment at the Bremen Drop Tower. Here, we report the experimental procedures for manufacturing the semiconductor-electrocatalyst device, details of the experimental set-up in the drop capsule and the experimental sequence during free fall.

Long-term space flights and cis-lunar research platforms require a sustainable and light life-support hardware which can be reliably employed outside the ...

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7.5K Views.  California Institute of Technology. Efficient solar-hydrogen production has recently been realized on functionalized semiconductor-electrocatalyst systems in a photoelectrochemical half-cell in microgravity environment at the Bremen Drop Tower. Here, we report the experimental procedures for manufacturing the semiconductor-electrocatalyst device, details of the experimental set-up in the drop capsule and the experimental sequence during free fall.

Video: Experimental Methods for Efficient Solar Hydrogen Production in Microgravity Environment

Analyzing Protein Dynamics Using Hydrogen Exchange Mass Spectrometry

All cellular processes depend on the functionality of proteins. Although the functionality of a given protein is the direct consequence of its unique amino acid sequence, it is only realized by the folding of the polypeptide chain into a single defined three-dimensional arrangement or more commonly into an ensemble of interconverting conformations. Investigating the connection between protein conformation and its function is therefore essential for a complete understanding of how proteins are able to fulfill their great variety of tasks. One possibility to study conformational changes a protein undergoes while progressing through its functional cycle is hydrogen-1H/2H-exchange in combination with high-resolution mass spectrometry (HX-MS). HX-MS is a versatile and robust method that adds a new dimension to structural information obtained by e.g. crystallography. It is used to study protein folding and unfolding, binding of small molecule ligands, protein-protein interactions, conformational changes linked to enzyme catalysis, and allostery. In addition, HX-MS is often used when the amount of protein is very limited or crystallization of the protein is not feasible. Here we provide a general protocol for studying protein dynamics with HX-MS and describe as an example how to reveal the interaction interface of two proteins in a complex. &#160;&#160;

Protein conformation and dynamics are key to understanding the relationship between protein structure and function. Hydrogen exchange coupled with high-resolution mass spectrometry is a versatile method to study the conformational dynamics of proteins as well as characterizing protein-ligand and protein-protein interactions, including contact interfaces and allosteric effects.

All cellular processes depend on the functionality of proteins. Although the functionality of a given protein is the direct consequence of its unique ...

Thin-layer Chromatographic (TLC) Separations and Bioassays of Plant Extracts to Identify Antimicrobial Compounds

A common screen for plant antimicrobial compounds consists of separating plant extracts by paper or thin-layer chromatography (PC or TLC), exposing the chromatograms to microbial suspensions (e.g. fungi or bacteria in broth or agar), allowing time for the microbes to grow in a humid environment, and visualizing zones with no microbial growth.&#160;The effectiveness of this screening method, known as bioautography, depends on both the quality of the chromatographic separation and the care taken with microbial culture conditions.&#160;This paper describes standard protocols for TLC and contact bioautography&#160;with a novel application to amino acid-fermenting bacteria. The extract is separated on flexible (aluminum-backed) silica TLC plates, and bands are visualized under ultraviolet (UV) light.&#160;Zones are cut out and incubated face down onto agar inoculated with the test microorganism.&#160;Inhibitory bands are visualized by staining the agar plates with tetrazolium red.&#160;The method is applied to the separation of red clover (Trifolium pratense cv. Kenland) phenolic compounds and their screening for activity against Clostridium sticklandii, a hyper ammonia-producing bacterium (HAB) that is native to the bovine rumen.&#160;The TLC methods apply to many types of plant extracts&#160;and other bacterial species (aerobic or anaerobic), as well as fungi, can be used as test organisms if culture conditions are modified to fit the growth requirements of the species.

Thin-layer Chromatographic TLC Separations and Bioassays of Plant Extracts to Identify Antimicrobial Compounds

Methods are described for thin-layer chromatographic (TLC) separation of plant extracts and contact bioautography to identify antibacterial metabolites. The methods are applied to the screening of red clover phenolic compounds inhibiting hyper&#160;ammonia-producing bacteria (HAB) native to the bovine rumen.

A common screen for plant antimicrobial compounds consists of separating plant extracts by paper or thin-layer chromatography (PC or TLC), exposing the ...

Metal-silicate Partitioning at High Pressure and Temperature: Experimental Methods and a Protocol to Suppress Highly Siderophile Element Inclusions

Estimates of the primitive upper mantle (PUM) composition reveal a depletion in many of the siderophile (iron-loving) elements, thought to result from their extraction to the core during terrestrial accretion. Experiments to investigate the partitioning of these elements between metal and silicate melts suggest that the PUM composition is best matched if metal-silicate equilibrium occurred at high pressures and temperatures, in a deep magma ocean environment. The behavior of the most highly siderophile elements (HSEs) during this process however, has remained enigmatic. Silicate run-products from HSE solubility experiments are commonly contaminated by dispersed metal inclusions that hinder the measurement of element concentrations in the melt. The resulting uncertainty over the true solubility and metal-silicate partitioning of these elements has made it difficult to predict their expected depletion in PUM. Recently, several studies have employed changes to the experimental design used for high pressure and temperature solubility experiments in order to suppress the formation of metal inclusions. The addition of Au (Re, Os, Ir, Ru experiments) or elemental Si (Pt experiments) to the sample acts to alter either the geometry or rate of sample reduction respectively, in order to avoid transient metal oversaturation of the silicate melt. This contribution outlines procedures for using the piston-cylinder and multi-anvil apparatus to conduct solubility and metal-silicate partitioning experiments respectively. A protocol is also described for the synthesis of uncontaminated run-products from HSE solubility experiments in which the oxygen fugacity is similar to that during terrestrial core-formation. Time-resolved LA-ICP-MS spectra are presented as evidence for the absence of metal-inclusions in run-products from earlier studies, and also confirm that the technique may be extended to investigate Ru. Examples are also given of how these data may be applied.

We present a procedure to determine the metal-silicate partitioning of siderophile elements, emphasizing techniques that suppress the formation of metal inclusions in experiments for the noble metals. The results of these experiments are used to demonstrate the effect of core-formation on the highly siderophile element composition of the mantle.

Estimates of the primitive upper mantle (PUM) composition reveal a depletion in many of the siderophile (iron-loving) elements, thought to result from ...

Supercritical Nitrogen Processing for the Purification of Reactive Porous Materials

Supercritical fluid extraction and drying methods are well established in numerous applications for the synthesis and processing of porous materials. Herein, nitrogen is presented as a novel supercritical drying fluid for specialized applications such as in the processing of reactive porous materials, where carbon dioxide and other fluids are not appropriate due to their higher chemical reactivity. Nitrogen exhibits similar physical properties in the near-critical region of its phase diagram as compared to carbon dioxide: a widely tunable density up to ~1 g ml-1, modest critical pressure (3.4 MPa), and small molecular diameter of ~3.6 &#197;. The key to achieving a high solvation power of nitrogen is to apply a processing temperature in the range of 80-150 K, where the density of nitrogen is an order of magnitude higher than at similar pressures near ambient temperature. The detailed solvation properties of nitrogen, and especially its selectivity, across a wide range of common target species of extraction still require further investigation. Herein we describe a protocol for the supercritical nitrogen processing of porous magnesium borohydride.

Nitrogen is an effective supercritical fluid for extraction or drying processes due to its small molecular size, high density in the near-liquid supercritical regime, and chemical inertness. We present a supercritical nitrogen drying protocol for the purification treatment of reactive, porous materials.

Supercritical fluid extraction and drying methods are well established in numerous applications for the synthesis and processing of porous materials. ...

Influence of Hybrid Perovskite Fabrication Methods on Film Formation, Electronic Structure, and Solar Cell Performance

Hybrid organic/inorganic halide perovskites have lately been a topic of great interest in the field of solar cell applications, with the potential to achieve device efficiencies exceeding other thin film device technologies. Yet, large variations in device efficiency and basic physical properties are reported. This is due to unintentional variations during film processing, which have not been sufficiently investigated so far. We therefore conducted an extensive study of the morphology and electronic structure of a large number of CH3NH3PbI3 perovskite where we show how the preparation method as well as the mixing ratio of educts methylammonium iodide and lead(II) iodide impact properties like film formation, crystal structure, density of states, energy levels, and ultimately the solar cell performance.

We present an extensive study on the effects of different fabrication methods for organic/inorganic perovskite thin films by comparing crystal structures, density of states, energy levels, and ultimately the solar cell performance.

Hybrid organic/inorganic halide perovskites have lately been a topic of great interest in the field of solar cell applications, with the potential to ...

Extraction of Ramie Fiber in Alkali Hydrogen Peroxide System Supported by Controlled-release Alkali Source

This protocol demonstrates a method for ramie fiber extraction by scouring raw ramie in an alkali hydrogen peroxide system supported by a controlled-release alkali source. The fiber extracted from ramie is a type of textile material of great importance. In previous studies, ramie fiber was extracted in an alkali hydrogen peroxide system supported only by sodium hydroxide.However, due to the strong alkalinity of sodium hydroxide, the oxidation reaction speed of hydrogen peroxide was difficult to control and thus resulted in great damage to the treated fiber. In this protocol, a controlled-release alkali source, which is composed of sodium hydroxide and magnesium hydroxide, is used to provide an alkali condition and buffer the pH value of the alkali hydrogen peroxidesystem. The substitution rate of magnesium hydroxide can adjust the pH value of the hydrogen peroxide system and has great influence on the fiber properties. The pH value and oxidation-reduction potential (ORP) value, which represents the oxidation ability of alkali hydrogen peroxide system, were monitored using a pH meter and ORP meter, respectively. The residual hydrogen peroxide content in the alkali hydrogen peroxide system during the extraction process and the chemical oxygen demand (COD) value of wastewater after fiber extraction are tested by KMnO4 titration method. The yield of fiber is measured using a precision electronic balance, and residual gums of fiber are tested by a chemical analysis method. The polymerization degree (PD value) of fiber is tested by an intrinsic viscosity method using the Ubbelohde viscometer. The tensile property of fiber, including tenacity, elongation, and rupture, is measured using a fiber strength instrument. Fourier transform infrared spectroscopy and X-ray diffraction are used to characterize the functional groups and crystal property of fiber. This protocol proves that the controlled-release alkali source can improve the properties of the fiber extracted in an alkali hydrogen peroxide system.

Presented here is a protocol for extraction of ramie fiber in alkali hydrogen peroxide system supported by controlled-release alkali source.

This protocol demonstrates a method for ramie fiber extraction by scouring raw ramie in an alkali hydrogen peroxide system supported by a ...

Key Factors Affecting the Performance of Sb2S3-sensitized Solar Cells During an Sb2S3 Deposition via SbCl3-thiourea Complex Solution-processing

Sb2S3 is considered as one of the emerging light absorbers that can be applied to next-generation solar cells because of its unique optical and electrical properties. Recently, we demonstrated its potential as next-generation solar cells by achieving a high photovoltaic efficiency of &#62; 6% in Sb2S3-sensitized solar cells using a simple thiourea (TU)-based complex solution method. Here, we describe the key experimental procedures for the deposition of Sb2S3 on a mesoporous TiO2 (mp-TiO2) layer using a SbCl3-TU complex solution in the fabrication of solar cells. First, the SbCl3-TU solution is synthesized by dissolving SbCl3 and TU in N,N-dimethylformamide at different molar ratios of SbCl3:TU. Then, the solution is deposited on as-prepared substrates consisting of mp-TiO2/TiO2-blocking layer/F-doped SnO2 glass by spin coating. Finally, to form crystalline Sb2S3, the samples are annealed in an N2-filled glove box at 300 &#176;C. The effects of the experimental parameters on the photovoltaic device performance are also discussed.

Key Factors Affecting the Performance of Sb2S3-sensitized Solar Cells During an Sb2S3 Deposition via SbCl3-thiourea Complex Solution-processing

This work provides a detailed experimental procedure for the deposition of Sb2S3 on a mesoporous TiO2 layer using a SbCl3-thiourea complex solution for applications in Sb2S3-sensitized solar cells. This article also determines key factors governing the deposition process.

Sb2S3 is considered as one of the emerging light absorbers that can be applied to next-generation solar cells because of its unique optical and electrical ...

Solution-Processed "Silver-Bismuth-Iodine" Ternary Thin Films for Lead-Free Photovoltaic Absorbers

Bismuth-based hybrid perovskites are regarded as promising photo-active semiconductors for environment-friendly and air-stable solar cell applications. However, poor surface morphologies and relatively high bandgap energies have limited their potential. Silver-bismuth-iodine (Ag-Bi-I) is a promising semiconductor for optoelectronic devices. Therefore, we demonstrate the fabrication of Ag-Bi-I ternary thin films using material solution processing. The resulting thin films exhibit controlled surface morphologies and optical bandgaps according to their thermal annealing temperatures. In addition, it has been reported that Ag-Bi-I ternary systems crystallize to AgBi2I7, Ag2BiI5, etc. according to the ratio of the precursor chemicals. The solution-processed AgBi2I7 thin films exhibit a cubic-phase crystal structure, dense, pinhole-free surface morphologies with grains ranging in size from 200 to 800 nm, and an indirect bandgap of 1.87 eV. The resultant AgBi2I7 thin films show good air stability and energy band diagrams, as well as surface morphologies and optical bandgaps suitable for lead-free and air-stable single-junction solar cells. Very recently, a solar cell with 4.3% power conversion efficiency was obtained by optimizing the Ag-Bi-I crystal compositions and solar cell device architectures.

Solution-Processed &quot;Silver-Bismuth-Iodine&quot; Ternary Thin Films for Lead-Free Photovoltaic Absorbers

Herein, we present detailed protocols for solution-processed silver-bismuth-iodine (Ag-Bi-I) ternary semiconductor thin films fabricated on TiO2-coated transparent electrodes and their potential application as air-stable and lead-free optoelectronic devices.

Bismuth-based hybrid perovskites are regarded as promising photo-active semiconductors for environment-friendly and air-stable solar cell applications. ...

Bio-inspired Polydopamine Surface Modification of Nanodiamonds and Its Reduction of Silver Nanoparticles

Surface functionalization of nanodiamonds (NDs) is still challenging due to the diversity of functional groups on the ND surfaces. Here, we demonstrate a simple protocol for the multifunctional surface modification of NDs by using mussel-inspired polydopamine (PDA) coating. In addition, the functional layer of PDA on NDs could serve as a reducing agent to synthesize and stabilize metal nanoparticles. Dopamine (DA) can self-polymerize and spontaneously form PDA layers on ND surfaces if the NDs and dopamine are simply mixed together. The thickness of a PDA layer is controlled by varying the concentration of DA. A typical result shows that a thickness of ~5 to ~15 nm of the PDA layer can be reached by adding 50 to 100 &#181;g/mL of DA to 100 nm ND suspensions. Furthermore, the PDA-NDs are used as a substrate to reduce metal ions, such as Ag[(NH3)2]+, to silver nanoparticles (AgNPs). The sizes of the AgNPs rely on the initial concentrations of Ag[(NH3)2]+. Along with an increase in the concentration of Ag[(NH3)2]+, the number of NPs increases, as well as the diameters of the NPs. In summary, this study not only presents a facile method for modifying the surfaces of NDs with PDA, but also demonstrates the enhanced functionality of NDs by anchoring various species of interest (such as AgNPs) for advanced applications.

A facile protocol is presented to functionalize the surfaces of nanodiamonds with polydopamine.

Surface functionalization of nanodiamonds (NDs) is still challenging due to the diversity of functional groups on the ND surfaces. Here, we demonstrate a ...

U2O5 Film Preparation via UO2 Deposition by Direct Current Sputtering and Successive Oxidation and Reduction with Atomic Oxygen and Atomic Hydrogen

We describe a method to produce U2O5 films in situ using the Labstation, a modular machine developed at JRC Karlsruhe. The Labstation, an essential part of the Properties of Actinides under Extreme Conditions laboratory (PAMEC), allows the preparation of films and studies of sample surfaces using surface analytical techniques such as X-ray and ultra-violet photoemission spectroscopy (XPS and UPS, respectively). All studies are made in situ, and the films, transferred under ultra-high vacuum from their preparation to an analyses chamber, are never in contact with the atmosphere. Initially, a film of UO2 is prepared by direct current (DC) sputter deposition on a gold (Au) foil then oxidized by atomic oxygen to produce a UO3 film. This latter is then reduced with atomic hydrogen to U2O5. Analyses are performed after each step involving oxidation and reduction, using high-resolution photoelectron spectroscopy to examine the oxidation state of uranium. Indeed, the oxidation and reduction times and corresponding temperature of the substrate during this process have severe effects on the resulting oxidation state of the uranium. Stopping the reduction of UO3 to U2O5 with single U(V) is quite challenging; first, uranium-oxygen systems exist in numerous intermediate phases. Second, differentiation of the oxidation states of uranium is mainly based on satellite peaks, whose intensity peaks are weak. Also, experimenters should be aware that X-ray spectroscopy (XPS) is a technique with an atomic sensitivity of 1% to 5%. Thus, it is important to obtain a complete picture of the uranium oxidation state with the entire spectra obtained on U4f, O1s, and the valence band (VB). Programs used in the Labstation include a linear transfer program developed by an outside company (see Table of Materials) as well as data acquisition and sputter source programs, both developed in-house.

U2O5 Film Preparation via UO2 Deposition by Direct Current Sputtering and Successive Oxidation and Reduction with Atomic Oxygen and Atomic Hydrogen

This protocol presents the preparation of U2O5 thin films obtained in situ under ultra-high vacuum. The process involves oxidation and reduction of UO2 films with atomic oxygen and atomic hydrogen, respectively.

We describe a method to produce U2O5 films in situ using the Labstation, a modular machine developed at JRC Karlsruhe. The Labstation, an essential part ...