a-protocol-for-electrochemical-evaluations-state-charge-diagnostics

A Protocol for Electrochemical Evaluations and State of Charge Diagnostics of a Symmetric Organic Redox Flow Battery

Redox flow batteries have been considered as one of the most promising stationary energy storage solutions for improving the reliability of the power grid ...

Joint Center for Energy Storage Research (JCESR)

Pacific Northwest National Laboratory

A strategy for controlling relative placements of molecules within multicomponent monolayers at the solution-HOPG interface is demonstrated. The monolayers assemble from complementary pairs of 1,5-bis-alkyldiether-anthracenes bearing self-repelling side chains. Each diether side chain suffers repulsive dipolar interactions if it adsorbs next to an identical side chain in the morphology normally assumed by 1,5-bis-substituted-anthracene monolayers. Complementary side-chain pairs experience attractive dipolar interactions when adsorbed as neighbors in the normal morphology monolayer. The repulsive and attractive forces spontaneously drive formation of a patterned monolayer at the solution-HOPG interface. Each molecule adsorbs in its own row, sandwiched between two rows of the complementary anthracene. These studies demonstrate the viability of using weak dipolar interactions to control molecular placement and monolayer morphology and to pattern multicomponent monolayers.

Dipolar control of monolayer morphology: spontaneous SAM patterning.

Anthracene Diels Alder adducts (DAa) bearing two long side chains (H-(CH(2))(22)O(CH(2))(6)OCH(2)-) at the 1- and 5-positions form self-assembled monolayers (SAMs) at the phenyloctane-highly oriented pyrolytic graphite (HOPG) interface. The long DAa side chains promote strong physisorption of the monolayer to HOPG and maintain the monolayer morphology upon rinsing or incubation in ethanol and air-drying of the substrate. Incorporating a carboxylic acid group on the DAa core enables capture of 1-4 nm diameter gold nanoparticles (AuNPs) provided (i) the monolayer containing DAa-carboxylic acids is treated with Cu(2+) ions and (ii) the organic coating on the AuNP contains carboxylic acids (11-mercaptoundecanoic acid, MUA-AuNP). AuNP capture by the monolayer proceeds with formation of Cu(2+)-carboxylate coordination complexes. The captured AuNP appear as mono- and multi-layered clusters at high coverage on HOPG. The surface density of the captured AuNPs can be adjusted from AuNP multi-layers to isolated AuNPs by varying incubation times, MUA-AuNP concentration, the number density of carboxylic acids in the monolayer, the number of MUA per AuNP, and post-incubation treatments.

Reactive capture of gold nanoparticles by strongly physisorbed monolayers on graphite.

The relationship between electrochemical performance of vanadium redox flow batteries (VRBs) and electrolyte composition is investigated, and the reasons for capacity decay over charge-discharge cycling are analyzed and discussed herein. The results show that the reasons for capacity fading over real charge-discharge cycling include not only the imbalanced vanadium active species, but also the asymmetrical valence of vanadium ions in positive and negative electrolytes. The asymmetrical valence of vanadium ions leads to a state-of-charge (SOC)-range decrease in positive electrolytes and a SOC-range increase in negative electrolytes. As a result, the higher SOC range in negative half-cells further aggravates capacity fading by creating a higher overpotential and possible hydrogen evolution. Based on this finding, we developed two methods for restoring lost capacity, thereby enabling long-term operation of VRBs to be achieved without the substantial loss of energy resulting from periodic total remixing of electrolytes.

Capacity decay and remediation of nafion-based all-vanadium redox flow batteries.

&#x96C7;&#x7528;&#x7535;&#x89E3;&#x8D28;&#x5305;&#x542B; Bi&#x3001; &#x94CB;&#x7EB3;&#x7C73;&#x7C92;&#x5B50;&#x540C;&#x6B65;&#x7684;&#x77F3;&#x58A8;&#x8868;&#x9762;&#x7535;&#x9540;&#x7535;&#x6781;&#x5728;&#x611F;&#x53D7;&#x5230;&#x5168;&#x9492;&#x6DB2;&#x6D41;&#x7535;&#x6C60; &#xFF08;VRFB&#xFF09; &#x7684;&#x64CD;&#x4F5C;&#x3002;&#x5BF9;&#x7535;&#x5316;&#x5B66;&#x6027;&#x80FD;&#x7684; VRFB &#x53CC;&#x7EB3;&#x7C73;&#x7C92;&#x5B50;&#x7684;&#x5F71;&#x54CD;&#x8FDB;&#x884C;&#x5F7B;&#x5E95;&#x8C03;&#x67E5;&#x3002;&#x5B83;&#x88AB;&#x8BC1;&#x5B9E;&#x53CC;&#x53EA;&#x662F;&#x51FA;&#x5E2D;&#x8D1F;&#x7535;&#x6781;&#x548C;&#x65B9;&#x4FBF;&#x4E86; V(II) &#x548C; V(III) &#x4E4B;&#x95F4;&#x7684;&#x6C27;&#x5316;&#x8FD8;&#x539F;&#x53CD;&#x5E94;&#x3002;&#x7136;&#x800C;&#xFF0C;Bi &#x7EB3;&#x7C73;&#x5FAE;&#x7C92;&#x663E;&#x8457;&#x63D0;&#x9AD8;&#x7535;&#x5316;&#x5B66;&#x6027;&#x80FD;&#x7684; VRFB &#x7EC6;&#x80DE;&#x901A;&#x8FC7;&#x52A0;&#x5F3A;&#x5446;&#x6EDE; V(II)/V(III) &#x6C27;&#x5316;&#x8FD8;&#x539F;&#x53CD;&#x5E94;&#xFF0C;&#x7279;&#x522B;&#x662F;&#x5728;&#x9AD8;&#x529F;&#x7387;&#x64CD;&#x4F5C;&#x4E0B;&#x7684;&#x52A8;&#x529B;&#x5B66;&#x3002;&#x80FD;&#x6E90;&#x6548;&#x7387;&#x88AB;&#x589E;&#x52A0;&#x5728;&#x9AD8;&#x7535;&#x6D41;&#x5BC6;&#x5EA6; (150 mA&middot;cm) &#x7531;&#x4E8E;&#x66F4;&#x5FEB;&#x7684;&#x7535;&#x8377;&#x8F6C;&#x79FB;&#x4E0E;&#x4E00;&#x4E2A;&#x6CA1;&#x6709; Bi &#x7684; 11%&#x3002;&#x7814;&#x7A76;&#x7ED3;&#x679C;&#x8868;&#x660E;&#x4F7F;&#x7528;&#x4EE3;&#x66FF;&#x8D35;&#x91D1;&#x5C5E;&#x7EB3;&#x7C73;&#x94CB;&#x7C89;&#x4F5C;&#x4E3A;&#x9AD8;&#x6027;&#x80FD;&#x7535;&#x6781;&#x7684; VRFB &#x5E94;&#x7528;&#x7A0B;&#x5E8F;&#x63D0;&#x4F9B;&#x5F88;&#x5927;&#x5E0C;&#x671B;&#x3002;

&#x94CB;&#x7EB3;&#x7C73;&#x88C5;&#x9970;&#x77F3;&#x58A8;&#x6478;&#x5168;&#x9492;&#x6DB2;&#x6D41;&#x7535;&#x6C60;&#x4F5C;&#x4E3A;&#x4E00;&#x79CD;&#x9AD8;&#x6027;&#x80FD;&#x7535;&#x6781;&#x3002;

Employing electrolytes containing Bi, bismuth nanoparticles are synchronously electrodeposited onto the surface of a graphite felt electrode during operation of an all-vanadium redox flow battery (VRFB). The influence of the Bi nanoparticles on the electrochemical performance of the VRFB is thoroughly investigated. It is confirmed that Bi is only present at the negative electrode and facilitates the redox reaction between V(II) and V(III). However, the Bi nanoparticles significantly improve the electrochemical performance of VRFB cells by enhancing the kinetics of the sluggish V(II)/V(III) redox reaction, especially under high power operation. The energy efficiency is increased by 11% at high current density (150 mAÂ·cm) owing to faster charge transfer as compared with one without Bi. The results suggest that using Bi nanoparticles in place of noble metals offers great promise as high-performance electrodes for VRFB application.

Bismuth nanoparticle decorating graphite felt as a high-performance electrode for an all-vanadium redox flow battery.

Employant des &eacute;lectrolytes contenant Bi, bismuth nanoparticules sont &eacute;lectrolytiques de mani&egrave;re synchrone sur la surface d&#39;un graphite senti &eacute;lectrode pendant le fonctionnement d&#39;une batterie de flux tout-vanadium redox (VRFB). L&#39;influence des nanoparticules Bi sur la performance &eacute;lectrochimique de la VRFB est soigneusement &eacute;tudi&eacute;e. Il est confirm&eacute; que le Bi n&#39;est pr&eacute;sent &agrave; l&#39;&eacute;lectrode n&eacute;gative et facilite la r&eacute;action d&#39;oxydor&eacute;duction entre lucratives et v (III). Toutefois, les nanoparticules Bi am&eacute;liorer consid&eacute;rablement la performance &eacute;lectrochimique des cellules VRFB en am&eacute;liorant la cin&eacute;tique de la r&eacute;action d&#39;oxydor&eacute;duction V(II)/V(III) lente, surtout sous l&#39;op&eacute;ration de haute puissance. L&#39;efficacit&eacute; &eacute;nerg&eacute;tique est augment&eacute;e de 11 % &agrave; haute densit&eacute; de courant (150 mA&middot;cm) en raison du transfert de charge plus rapide par rapport &agrave; l&#39;autre sans Bi. Les r&eacute;sultats sugg&egrave;rent qu&#39;utilisant des nanoparticules de Bi &agrave; la place de m&eacute;taux nobles offre tr&egrave;s prometteur comme &eacute;lectrodes de haute performance pour l&#39;application de VRFB.

Nanoparticules de bismuth d&eacute;coration graphite ressenti comme une &eacute;lectrode haute performance pour une batterie de flux tout-vanadium redox.

Impiegando elettroliti contenenti Bi, bismuto nanoparticelle sono electrodeposited in modo sincrono sulla superficie di una grafite sentivo elettrodo durante il funzionamento di una batteria di flusso all-vanadio redox (VRFB). L&#39;influenza delle nanoparticelle Bi sulle prestazioni elettrochimiche del VRFB &egrave; approfondito. &Egrave; confermato che Bi &egrave; solo presente all&#39;elettrodo negativo e facilita la reazione redox tra V(II) e V(III). Tuttavia, le nanoparticelle Bi migliorano significativamente le prestazioni elettrochimiche di cellule VRFB migliorando la cinetica della reazione redox V(II)/V(III) pigra, specialmente sotto funzionamento ad alta potenza. L&#39;efficienza energetica &egrave; aumentata dell&#39;11% ad alta densit&agrave; di corrente (150 mA&middot;cm) a causa del trasferimento della carica pi&ugrave; velocemente rispetto ad uno senza Bi. I risultati suggeriscono che usando nanoparticelle Bi al posto di metalli nobili offre grande promessa come elettrodi ad alte prestazioni per applicazioni VRFB.

Bismuto nanoparticella decorazione grafite sentivo come un elettrodo ad alte prestazioni per una batteria di flusso all-vanadio redox.

&#x96FB;&#x89E3;&#x8CEA;&#x3092;&#x7528;&#x3044;&#x305F;&#x30CA;&#x30CE;&#x7C92;&#x5B50;&#x304C;&#x540C;&#x671F;&#x7684;&#x306B;&#x306F;&#x30B0;&#x30E9;&#x30D5;&#x30A1;&#x30A4;&#x30C8;&#x8868;&#x9762;&#x4E0A;&#x306B;&#x96FB;&#x6790;&#x306F;&#x30D3;&#x30B9;&#x30DE;&#x30B9;&#x3092;&#x542B;&#x3080; Bi &#x306F;&#x3059;&#x3079;&#x3066;&#x30D0;&#x30CA;&#x30B8;&#x30A6;&#x30E0; &#x30EC;&#x30C9;&#x30C3;&#x30AF;&#x30B9; &#x30D5;&#x30ED;&#x30FC;&#x96FB;&#x6C60; (VRFB) &#x306E;&#x64CD;&#x4F5C;&#x4E2D;&#x306B;&#x96FB;&#x6975;&#x3092;&#x611F;&#x3058;&#x305F;&#x3002;VRFB &#x306E;&#x96FB;&#x6C17;&#x5316;&#x5B66;&#x6027;&#x80FD;&#x306B;&#x53CA;&#x307C;&#x3059; Bi &#x30CA;&#x30CE;&#x7C92;&#x5B50;&#x3092;&#x5FB9;&#x5E95;&#x7684;&#x306B;&#x8ABF;&#x67FB;&#x3057;&#x307E;&#x3059;&#x3002;Bi &#x3060;&#x3051;&#x3067;&#x5426;&#x5B9A;&#x7684;&#x306A;&#x96FB;&#x6975;&#x3042;&#x308B;&#x3057;&#x3001;V(II) &#x3068; V(III) &#x306E;&#x9593;&#x306E;&#x9178;&#x5316;&#x9084;&#x5143;&#x53CD;&#x5FDC;&#x3092;&#x4FC3;&#x9032;&#x3059;&#x308B;&#x3053;&#x3068;&#x3092;&#x78BA;&#x8A8D;&#x3057;&#x307E;&#x3059;&#x3002;&#x305F;&#x3060;&#x3057;&#x3001;Bi &#x30CA;&#x30CE;&#x7C92;&#x5B50;&#x5927;&#x5E45;&#x306B; VRFB &#x30BB;&#x30EB;&#x306E;&#x96FB;&#x6C17;&#x5316;&#x5B66;&#x6027;&#x80FD;&#x4F4E;&#x8FF7; V(II)/V(III) &#x306E;&#x9178;&#x5316;&#x9084;&#x5143;&#x53CD;&#x5FDC;&#x306F;&#x3001;&#x7279;&#x306B;&#x9AD8;&#x96FB;&#x529B;&#x306E;&#x4E0B;&#x3067;&#x306E;&#x53CD;&#x5FDC;&#x901F;&#x5EA6;&#x5411;&#x4E0A;&#x3057;&#x307E;&#x3059;&#x3002;&#x30A8;&#x30CD;&#x30EB;&#x30AE;&#x30FC;&#x52B9;&#x7387;&#x306F;&#x3001;&#x9AD8;&#x96FB;&#x6D41;&#x5BC6;&#x5EA6; (150 mA&middot;cm) &#x53CC;&#x305B;&#x305A;&#x306B; 1 &#x3064;&#x3068;&#x6BD4;&#x8F03;&#x3057;&#x3066;&#x9AD8;&#x901F;&#x306E;&#x96FB;&#x8377;&#x79FB;&#x52D5;&#x306B;&#x3088;&#x308A; 11 &#xFF05; &#x306B;&#x5897;&#x52A0;&#x3057;&#x307E;&#x3059;&#x3002;&#x8CB4;&#x91D1;&#x5C5E;&#x306E;&#x4EE3;&#x308F;&#x308A;&#x306B; Bi &#x30CA;&#x30CE;&#x7C92;&#x5B50;&#x3092;&#x4F7F;&#x7528;&#x3057;&#x3066;&#x5049;&#x5927;&#x306A;&#x7D04;&#x675F; VRFB &#x30A2;&#x30D7;&#x30EA;&#x30B1;&#x30FC;&#x30B7;&#x30E7;&#x30F3;&#x7528;&#x306E;&#x9AD8;&#x30D1;&#x30D5;&#x30A9;&#x30FC;&#x30DE;&#x30F3;&#x30B9;&#x306E;&#x96FB;&#x6975;&#x3068;&#x3057;&#x3066;&#x63D0;&#x4F9B;&#x3059;&#x308B;&#x3053;&#x3068;&#x304C;&#x793A;&#x5506;&#x3055;&#x308C;&#x307E;&#x3057;&#x305F;&#x3002;

&#x9ED2;&#x925B;&#x3092;&#x98FE;&#x308B;&#x30D3;&#x30B9;&#x30DE;&#x30B9; &#x30CA;&#x30CE;&#x7C92;&#x5B50;&#x3001;&#x9AD8;&#x30D1;&#x30D5;&#x30A9;&#x30FC;&#x30DE;&#x30F3;&#x30B9;&#x306E;&#x96FB;&#x6975;&#x3068;&#x3057;&#x3066;&#x3001;&#x3059;&#x3079;&#x3066;&#x30D0;&#x30CA;&#x30B8;&#x30A6;&#x30E0; &#x30EC;&#x30C9;&#x30C3;&#x30AF;&#x30B9; &#x30D5;&#x30ED;&#x30FC;&#x96FB;&#x6C60;&#x3092;&#x611F;&#x3058;&#x305F;&#x3002;

&#xC804;&#xD574;&#xC9C8; &#xCC44;&#xC6A9; &#xD3EC;&#xD568; Bi &#xBE44;&#xC2A4;&#xBB34;&#xD2B8; &#xB098;&#xB178; &#xC785;&#xC790; &#xD45C;&#xBA74;&#xC5D0; &#xD751;&#xC5F0;&#xC758; &#xD30C;&#xB77C; &#xB3D9;&#xAE30;&#xC801;&#xC73C;&#xB85C; &#xBAA8;&#xB4E0; &#xBC14;&#xB098;&#xB4D0; redox &#xD750;&#xB984; &#xBC30;&#xD130;&#xB9AC; (VRFB)&#xC758; &#xC791;&#xC5C5; &#xC911; &#xC804;&#xADF9;&#xC744; &#xB290;&#xAF08;&#xB2E4;. VRFB&#xC758; &#xC804;&#xAE30; &#xD654;&#xD559;&#xC801; &#xC131;&#xB2A5;&#xC5D0; Bi &#xB098;&#xB178; &#xC785;&#xC790;&#xC758; &#xC601;&#xD5A5; &#xCCA0;&#xC800; &#xD558; &#xAC8C; &#xC870;&#xC0AC; &#xD588;&#xB2E4;. Bi&#xB294; &#xBD80;&#xC815;&#xC801;&#xC778; &#xC804;&#xADF9;&#xC5D0; &#xC874;&#xC7AC;&#xB9CC; &#xD558; &#xACE0; V(II)&#xC640; V(III) &#xC0AC;&#xC774; redox &#xBC18;&#xC751;&#xC744; &#xC6A9;&#xC774; &#xD558; &#xAC8C; &#xD655;&#xC778; &#xD569;&#xB2C8;&#xB2E4;. &#xADF8;&#xB7EC;&#xB098; Bi &#xB098;&#xB178; &#xC785;&#xC790;&#xB294; &#xD06C;&#xAC8C; &#xB192;&#xC740; &#xC804;&#xC6D0; &#xC791;&#xB3D9; &#xC0C1;&#xD0DC;&#xC5D0;&#xC11C; &#xD2B9;&#xD788; &#xBD80; &#xC9C4;&#xD55C; V(II)/V(III) redox &#xBC18;&#xC751;&#xC758; &#xC18D;&#xB3C4; &#xB860;&#xC744; &#xAC15;&#xD654; &#xD558; &#xC5EC; VRFB &#xC138;&#xD3EC;&#xC758; &#xC804;&#xAE30; &#xD654;&#xD559;&#xC801; &#xC131;&#xB2A5; &#xD5A5;&#xC0C1;. &#xC5D0;&#xB108;&#xC9C0; &#xD6A8;&#xC728;&#xC740; &#xB192;&#xC740; &#xC804;&#xB958; &#xBC00;&#xB3C4; (150 mA&middot;cm) &#xD558;&#xB098; &#xC5C6;&#xC774; Bi&#xC5D0; &#xBE44;&#xD574; &#xBE60;&#xB978; &#xCDA9;&#xC804; &#xC804;&#xC1A1; &#xB54C;&#xBB38;&#xC5D0; 11% &#xC99D;&#xAC00; &#xD588;&#xB2E4;. &#xACB0;&#xACFC; Bi &#xADC0;&#xAE08;&#xC18D; &#xB300;&#xC2E0; &#xB098;&#xB178; &#xC785;&#xC790;&#xB97C; &#xC0AC;&#xC6A9; &#xD558; &#xC5EC; VRFB &#xC751;&#xC6A9; &#xD504;&#xB85C;&#xADF8;&#xB7A8;&#xC5D0; &#xB300; &#xD55C; &#xB192;&#xC740;-&#xC131;&#xB2A5; &#xC804;&#xADF9;&#xC73C;&#xB85C; &#xC704;&#xB300;&#xD55C; &#xC57D;&#xC18D; &#xC81C;&#xACF5; &#xAC83;&#xC774; &#xC88B;&#xC2B5;&#xB2C8;&#xB2E4;.

&#xBE44;&#xC2A4;&#xBB34;&#xD2B8; &#xB098;&#xB178; &#xC785;&#xC790; &#xD751;&#xC5F0;&#xC744; &#xAFB8;&#xBBF8;&#xB294; &#xBAA8;&#xB4E0; &#xBC14;&#xB098;&#xB4D0; redox &#xD750;&#xB984; &#xBC30;&#xD130;&#xB9AC;&#xC5D0; &#xB300; &#xD55C; &#xB192;&#xC740;-&#xC131;&#xB2A5; &#xC804;&#xADF9;&#xC73C;&#xB85C; &#xB290;&#xAF08;&#xB2E4;.

Empleando los electrolitos que contienen Bi, bismuto nanopart&iacute;culas son electrodepositadas sincr&oacute;nicamente en la superficie de un grafito electrodo del fieltro durante el funcionamiento de una bater&iacute;a de flujo redox de todos-vanadio (VRFB). La influencia de las nanopart&iacute;culas de Bi en el comportamiento electroqu&iacute;mico de la VRFB es investigada a fondo. Se confirma que Bi s&oacute;lo est&aacute; presente en el electrodo negativo y facilita la reacci&oacute;n redox entre V(II) y V(III). Sin embargo, las nanopart&iacute;culas de Bi mejoran significativamente el rendimiento electroqu&iacute;mico de c&eacute;lulas VRFB mejorando la cin&eacute;tica de la reacci&oacute;n de redox V(II)/V(III) lenta, especialmente bajo la operaci&oacute;n de alta potencia. La eficiencia de energ&iacute;a se incrementa en un 11% en alta densidad de corriente (mA&middot;cm 150) debido a la transferencia de la carga m&aacute;s r&aacute;pida en comparaci&oacute;n con uno sin Bi. Los resultados sugieren que usando nanopart&iacute;culas de Bi en lugar de metales nobles ofrece una gran promesa como electrodos de alto rendimiento para aplicaciones de VRFB.

Nanopart&iacute;culas de bismuto decoraci&oacute;n grafito se sent&iacute;an como un electrodo de alto rendimiento para una bater&iacute;a de flujo redox de todos-vanadio.

A powerful low-cost electrocatalyst, nanorod Nb2O5, is synthesized using the hydrothermal method with monoclinic phases and simultaneously deposited on the surface of a graphite felt (GF) electrode in an all vanadium flow battery (VRB). Cyclic voltammetry (CV) study confirmed that Nb2O5 has catalytic effects toward redox couples of V(II)/V(III) at the negative side and V(IV)/V(V) at the positive side to facilitate the electrochemical kinetics of the vanadium redox reactions. Because of poor conductivity of Nb2O5, the performance of the Nb2O5 loaded electrodes is strongly dependent on the nanosize and uniform distribution of catalysts on GF surfaces. Accordingly, an optimal amount of W-doped Nb2O5 nanorods with minimum agglomeration and improved distribution on GF surfaces are established by adding water-soluble compounds containing tungsten (W) into the precursor solutions. The corresponding energy efficiency is enhanced by ∼10.7% at high current density (150 mA·cm(-2)) as compared with one without catalysts. Flow battery cyclic performance also demonstrates the excellent stability of the as prepared Nb2O5 catalyst enhanced electrode. These results suggest that Nb2O5-based nanorods, replacing expensive noble metals, uniformly decorating GFs holds great promise as high-performance electrodes for VRB applications.

Nanorod niobium oxide as powerful catalysts for an all vanadium redox flow battery.

The results of the investigation of the capacity decay mechanism of vanadium redox flow batteries with microporous separators as membranes are reported. The investigation focuses on the relationship between the electrochemical performance and electrolyte compositions at both the positive and negative half-cells. Although the concentration of total vanadium ions remains nearly constant at both sides over cycling, the net transfer of solution from one side to the other and thus the asymmetrical valance of vanadium ions caused by the subsequent disproportionate self-discharge reactions at both sides lead to capacity fading. Through in situ monitoring of the hydraulic pressure of the electrolyte during cycling at both sides, the convection was found to arise from differential hydraulic pressures at both sides of the separators and plays a dominant role in capacity decay. A capacity-stabilizing method is developed and was successfully demonstrated through the regulation of gas pressures in both electrolyte tanks.

Capacity decay mechanism of microporous separator-based all-vanadium redox flow batteries and its recovery.

Ferrocene (Fc) and N-(ferrocenylmethyl)-N,N-dimethyl-N-ethylammonium bistrifluoromethyl-sulfonimide (Fc1N112-TFSI) were dissolved in carbonate solvents and self-diffusion coefficients (D) of solutes and solvents were measured by (1)H and (19)F pulsed field gradient nuclear magnetic resonance (NMR) spectroscopy. The organic solvents were propylene carbonate (PC), ethyl methyl carbonate (EMC), and a ternary mixture that also includes ethylene carbonate (EC). Results from NMR studies over the temperature range of 0-50 °C and for various concentrations (0.25-1.7 M) of Fc1N112-TFSI are compared to values of D simulated with classical molecular dynamics (MD). The measured self-diffusion coefficients gradually decreased as the Fc1N112-TFSI concentration increased in all solvents. Since TFSI(-) has fluoromethyl groups (CF3), D(TFSI) could be measured separately and the values found are larger than those for D(Fc1N112) in all samples measured. The EC, PC, and EMC have the same D in the neat solvent mixture and when Fc is dissolved in EC/PC/EMC at a concentration of 0.2 M, probably due to the interactions between common carbonyl structures within EC, PC, and EMC. A difference in D (D(PC) < D(EC) < D(EMC)), and both a higher E(a) for translational motion and higher effective viscosity for PC in the mixture containing Fc1N112-TFSI reflect the interaction between PC and Fc1N112(+), which is a relatively stronger interaction than that between Fc1N112(+) and other solvent species. In the EC/PC/EMC solution that is saturated with Fc1N112-TFSI, we find that D(PC) = D(EC) = D(EMC) and Fc1N112(+) and all components of the EC/PC/EMC solution have the same E(a) for translational motion, while the ratio D(EC/PC/EMC)/D(Fc1N112) is approximately 3. These results reflect the lack of available free volume for independent diffusion in the saturated solution. The Fc1N112(+) transference numbers lie around 0.4 and increase slightly as the temperature is increased in the PC and EMC solvents. The trends observed for D from simulations are in good agreement with experimental results and provide molecular level understanding of the solvation structure of Fc1N112-TFSI dissolved in EC/PC/EMC.

Diffusional motion of redox centers in carbonate electrolytes.

A TEMPO-based non-aqueous electrolyte with the TEMPO concentration as high as 2.0 m is demonstrated as a high-energy-density catholyte for redox flow battery applications. With a hybrid anode, Li|TEMPO flow cells using this electrolyte deliver an energy efficiency of ca. 70% and an impressively high energy density of 126 W h L(-1) .

TEMPO-based catholyte for high-energy density nonaqueous redox flow batteries.

Nonaqueous redox flow batteries hold the promise of achieving higher energy density because of the broader voltage window than aqueous systems, but their current performance is limited by low redox material concentration, cell efficiency, cycling stability, and current density. We report a new nonaqueous all-organic flow battery based on high concentrations of redox materials, which shows significant, comprehensive improvement in flow battery performance. A mechanistic electron spin resonance study reveals that the choice of supporting electrolytes greatly affects the chemical stability of the charged radical species especially the negative side radical anion, which dominates the cycling stability of these flow cells. This finding not only increases our fundamental understanding of performance degradation in flow batteries using radical-based redox species, but also offers insights toward rational electrolyte optimization for improving the cycling stability of these flow batteries.

Radical Compatibility with Nonaqueous Electrolytes and Its Impact on an All-Organic Redox Flow Battery.

We report a series of ionically modified ferrocene compounds for hybrid lithium-organic non-aqueous redox flow batteries, based on the ferrocene/ferrocenium redox couple as the active catholyte material. Tetraalkylammonium ionic moieties were incorporated into the ferrocene structure, in order to enhance the solubility of the otherwise relatively insoluble ferrocene. The effect of various counter anions of the tetraalkylammonium ionized species appended to the ferrocene, such as bis(trifluoromethanesulfonyl)imide, hexafluorophosphate, perchlorate, tetrafluoroborate, and dicyanamide on the solubility of the ferrocene was investigated. The solution chemistry of the ferrocene species was studied, in order to understand the mechanism of solubility enhancement. Finally, the electrochemical performance of these ionized ferrocene species was evaluated and shown to have excellent cell efficiency and superior cycling stability.

Anion-Tunable Properties and Electrochemical Performance of Functionalized Ferrocene Compounds.

Hydrogen production from seawater and solar energy based on photoelectrochemical cells is extremely attractive due to earth-abundance of seawater and solar radiation. Herein, we report the successful fabrication of novel inorganic-organic 2D/2D WO3/g-C3N4 nanosheet arrays (WO3/g-C3N4 NSAs) grown on a FTO substrate via a facile hydrothermal growth and deposition-annealing process, and their application in natural seawater splitting. The results indicate that the WO3/g-C3N4 NSAs exhibit a photocurrent density of 0.73 mA cm(-2) at 1.23 V versus RHE under AM 1.5G (100 mW cm(-2)) illumination, which is 2-fold higher than that of WO3 NSAs. More importantly, the WO3/g-C3N4 NSA photoanode is quite stable during seawater splitting and the photocurrent density does not substantially decrease after continuous illumination for 3600 s. The remarkably enhanced performance originates primarily from the formation of the WO3/g-C3N4 heterojunction between WO3 and g-C3N4 nanosheets, which accelerates charge transfer and separation, and prolongs the lifetime of electrons as demonstrated by EIS and Mott-Schottky analyses. Finally, a possible mechanism for the improved performance was proposed and discussed.

Construction of inorganic-organic 2D/2D WO₃/g-C₃N₄ nanosheet arrays toward efficient photoelectrochemical splitting of natural seawater.

Highly photoactive and durable photoanode materials are the key to photoelectrochemical water splitting. In this paper, hierarchically branched Fe2O3@TiO2 nanorod arrays (denoted as Fe2O3@TiO2 BNRs) composed of a long Fe2O3 trunk and numerous short TiO2 nanorod branches were fabricated and used as photoanodes for water splitting. Significant improvement of photoelectrochemical water splitting performance was observed based on Fe2O3@TiO2 BNRs. The photocurrent density of Fe2O3@TiO2 BNRs reaches up to 1.3 mA cm(-2) at 1.23 V versus RHE, which is 10 times higher than that of pristine Fe2O3 nanorod arrays under the same conditions. Furthermore, an obvious cathodic shift in the onset potential of photocurrent was observed in the Fe2O3@TiO2 BNRs. More significantly, the Fe2O3@TiO2 BNRs are quite stable even after 3600 s continuous illumination, and the photocurrent density shows almost no decay. Finally, a tentative mechanism was proposed to explain the superior performance of Fe2O3@TiO2 BNRs for PEC water splitting and discussed in detail on the basis of our experimental results.

Hierarchically branched Fe2O3@TiO2 nanorod arrays for photoelectrochemical water splitting: facile synthesis and enhanced photoelectrochemical performance.

Aims. MicroRNAs (miRNAs) are involved in the pathogenesis of coronary artery disease (CAD). The objective of this study is to determine plasma levels of miR-10a in CAD and analyze its association with the severity of CAD. Materials and Methods. Plasma miR-10a levels in 60 CAD patients including stable angina pectoris (SAP) (n = 29), unstable angina pectoris (UAP) or non-ST elevation myocardial infarction (MI) (NSTEMI) (n = 17), or ST elevation MI (STEMI) (n = 14) and 20 non-CAD subjects were assessed by real-time polymerase chain reaction (qRT-PCR), and associations of miR-10a levels with risk factors of CAD and its severity were analyzed. Results. The qRT-PCR results showed that plasma miR-10a levels were decreased in CAD patients, and CAD with high SYNTAX scores or STEMI was significantly associated with lower miR-10a levels. Conclusions. Lower plasma miR-10a levels were negatively associated with the presence as well as severity of CAD, and plasma miR-10a can act as a potential biomarker for estimating the presence and severity of CAD.

Plasma miR-10a: A Potential Biomarker for Coronary Artery Disease.

The aim of this study is to determine miR-22 expression levels in peripheral blood mononuclear cells (PBMCs) of patients with coronary artery disease (CAD) and to investigate whether MCP-1 expression is regulated by miR-22. miR-22 expression in PBMCs from 60 CAD patients including stable angina pectoris (SAP) (n = 29), unstable angina pectoris (UAP) or non-ST elevation myocardial infarction (NSTEMI) (n = 17), or ST-elevation MI (STEMI) (n = 14) and 20 non-CAD subjects by real-time polymerase chain reaction (qRT-PCR). The luciferase activity assays were employed to determine whether miR-22 binds to 3'UTR of MCP-1. miR-22 mimics and inhibitors were transfected into healthy PBMCs. MCP-1 mRNA and protein levels were determined by qRT-PCR and enzyme-linked immuno sorbent assay, respectively. The qRT-PCR results showed that miR-22 levels in PBMCs were decreased in CAD patients, and MCP-1 was augmented in CAD patients and was inversely correlated with miR-22 levels. The luciferase activity assays indicated that MCP-1 was a target of miR-22. Overexpression of miR-22 could significantly repress MCP-1 expression at both mRNA and protein levels in PBMCs, whereas inhibition of miR-22 showed the opposite effects. This study revealed that miR-22 is downregulated in PBMCs from patients with CAD and that miR-22 may participate in inflammatory response by targeting MCP-1, therefore contributing CAD.

miR-22 contributes to the pathogenesis of patients with coronary artery disease by targeting MCP-1: An observational study.

In advanced electrical grids of the future, electrochemically rechargeable fluids of high energy density will capture the power generated from intermittent sources like solar and wind. To meet this outstanding technological demand there is a need to understand the fundamental limits and interplay of electrochemical potential, stability, and solubility in low-weight redox-active molecules. By generating a combinatorial set of 1,4-dimethoxybenzene derivatives with different arrangements of substituents, we discovered a minimalistic structure that combines exceptional long-term stability in its oxidized form and a record-breaking intrinsic capacity of 161 mAh/g. The nonaqueous redox flow battery has been demonstrated that uses this molecule as a catholyte material and operated stably for 100 charge/discharge cycles. The observed stability trends are rationalized by mechanistic considerations of the reaction pathways.

The lightest organic radical cation for charge storage in redox flow batteries.

The microstructure of perfluorinated sulfonic acid proton-exchange membranes such as Nafion significantly affects their transport properties and performance in a vanadium redox-flow battery (VRB). In this work, Nafion membranes with various equivalent weights ranging from 1000 to 1500 are prepared and the morphology-property-performance relationship is investigated. NMR and small-angle X-ray scattering studies revealed their composition and morphology variances, which lead to major differences in key transport properties related to proton conduction and vanadium-ion permeation. Their performances are further characterized as VRB membranes. On the basis of this understanding, a new perfluorosulfonic acid membrane is designed with optimal pore geometry and thickness, leading to higher ion selectivity and lower cost compared with the widely used Nafion 115. Excellent VRB single-cell performance (89.3% energy efficiency at 50 mA·cm(-2)) was achieved along with a stable cyclical capacity over prolonged cycling.

Xiaoliang Wei

Joint Center for Energy Storage Research (JCESR)

A Protocol for Electrochemical Evaluations and State of Charge Diagnostics of a Symmetric Organic Redox Flow Battery