performing-situ-closed-cell-gas-reactions-transmission-electron

Performing <em>In Situ</em> Closed-Cell Gas Reactions in the Transmission Electron Microscope

Gas reactions studied by in situ electron microscopy can be used to capture the real-time morphological and microchemical transformations of materials at ...

National Renewable Energy Laboratory

Low-cost inorganic solar cells: from ink to printed device.

We present an expansion of the mixed-valence iodide reduction method for the synthesis of Ge nanocrystals (NCs) to incorporate low levels (∼1 mol %) of groups III, IV, and V elements to yield main-group element-alloyed Ge NCs (Ge1-xEx NCs). Nearly every main-group element (E) that surrounds Ge on the periodic table (Al, P, Ga, As, In, Sn, and Sb) may be incorporated into Ge1-xEx NCs with remarkably high E incorporation into the product (>45% of E added to the reaction). Importantly, surface chemistry modification via ligand exchange allowed conductive films of Ge1-xEx NCs to be prepared, which exhibit conductivities over large distances (25 μm) relevant to optoelectronic device development of group IV NC thin films. 

Surface Chemistry Exchange of Alloyed Germanium Nanocrystals: A Pathway Toward Conductive Group IV Nanocrystal Films.

Transition metal phosphide catalysts such as nickel phosphide (NiP) have shown excellent activities for the hydrogen evolution reaction, but they have primarily been studied in strongly acidic or alkaline electrolytes. In microbial electrolysis cells (MECs), however, the electrolyte is usually a neutral pH to support the bacteria. Carbon-supported phase-pure NiP nanoparticle catalysts (NiP/C) were synthesized using solution-phase methods and their performance was compared to Pt/C and Ni/C catalysts in MECs. The NiP/C produced a similar quantity of hydrogen over a 24 h cycle (0.29 ± 0.04 L-H/L-reactor) as that obtained using Pt/C (0.32 ± 0.03 L-H/L) or Ni/C (0.29 ± 0.02 L-H/L). The mass normalized current density of the NiP/C was 14 times higher than that of the Ni/C, and the NiP/C exhibited stable performance over 11 days. NiP/C may therefore be a useful alternative to Pt/C or other Ni-based catalysts in MECs due to its chemical stability over time.

Application of phase-pure nickel phosphide nanoparticles as cathode catalysts for hydrogen production in microbial electrolysis cells.

Transition metal carbides (TMCs) have demonstrated outstanding potential for utilization in a wide range of catalytic applications because of their inherent multifunctionality and tunable composition. However, the harsh conditions required to prepare these materials have limited the scope of synthetic control over their physical properties. The development of low-temperature, carburization-free routes to prepare TMCs would unlock the versatility of this class of materials, enhance our understanding of their physical properties, and enable their cost-effective production at industrial scales. Here, we report an exceptionally mild and scalable solution-phase synthesis route to phase-pure molybdenum carbide (α-MoC) nanoparticles (NPs) in a continuous flow millifluidic reactor. We exploit the thermolytic decomposition of Mo(CO) in the presence of a surface-stabilizing ligand and a high boiling point solvent to yield MoC NPs that are colloidally stable and resistant to bulk oxidation in air. To demonstrate the utility of this synthetic route to prepare catalytically active TMC NPs, we evaluated the thermochemical CO hydrogenation performance of α-MoC NPs dispersed on an inert carbon support. The α-MoC/C catalyst exhibited a 2-fold increase in both activity on a per-site basis and selectivity to C products as compared to the bulk α-MoC analogue.

Susan E. Habas

Catalytic Carbon Transformation & Scale-up

National Renewable Energy Laboratory

Performing In Situ Closed-Cell Gas Reactions in the Transmission Electron Microscope

Susan E. Habas

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National Renewable Energy Laboratory

Performing In Situ Closed-Cell Gas Reactions in the Transmission Electron Microscope

Catalytic Carbon Transformation & Scale-up