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Electrochemical water oxidation over high-efficiency (Ca, Mg, or Y) doped lithium metal (Ni) phosphate electrocatalysts

Direct hydrazine fuel cells (DHFC) insist on the evolved and persistent electrocatalysts for anodic hydrazine oxidation reaction (HzOR). Herein, PdO promoted CuO heterostructures supported on γ‐Al2O3 are depicted as efficient electrocatalysts for HzOR. γ‐Al2O3 is prepared by precipitation method while metal precursors are incorporated by co‐impregnation technique. Physiochemically characterized PdO‐CuO/Al2O3 mesoporous composites displayed large electrochemical active surface area (ECSA) i. e., 0.18 cm2, high current density (j) i. e., 35.7 mA cm−2, larger diffusion coefficient (D°) i. e., 29.3×10−4 (cm2s−1), large apparent rate constant (kapp) i. e., 13.2 cm−1 with low charge transfer resistance (Rct) i. e., 3.6 kΩ shown by the best catalyst i. e., 1 % PdO‐CuO/Al2O3. Cyclic voltammetry indicated that the fabricated working electrodes offer high efficiency towards HzOR in alkaline medium in such a way that 1 % PdO‐CuO/Al2O3 produced 600 times higher oxidation current than CuO/Al2O3 composite. Owing to stability and reproducibility, PdO modified CuO/Al2O3 would achieve a huge catalytic significance in multiple electrochemical oxidation reactions with economic and ecological benefits. [ABSTRACT FROM AUTHOR]

Summary: The oxygen reduction and evolution reaction (ORR/OER), are the keystones for many energy generating and storage devices, have influence with many electrocatalytic reactions. The sluggish kinetics of these reaction is a challenging situation on the surface of electrodes which imposes large over‐potential and affects the energy output of fuel cells. Although the platinum‐based electrode materials have excellent activity toward ORR/OER but their high cost limits commercialization of fuel cells. To deal with this problem, platinum‐free electrode materials has aroused the considerations of scientists. The present work is proposed to study the oxygen reduction reaction and water oxidation on the surface of xAg2O‐yPrO2/γ‐Al2O3/Glassy‐Carbon. The ORR was studied electrochemically via cyclic voltammetry on the surface of these nano‐catalysts while the OER was investigated via cyclic voltammetry and linear sweep voltammetry in alkaline media. The mechanism of ORR on catalysts surface was enquired and the results indicate that ORR followed two electrons pathway in case of 10PrO2/γ‐Al2O3/Glassy‐Carbon while four electrons reduction pathway is identified on surface of others catalysts which divulged that addition of silver with praseodymium shifted the mechanism from 2e− to 4e− pathway. The electrocatalysts featured the stability during multiple scans and no corrosion of electrode in OER/ORR is observed. Different kinetic parameters for both reactions are determined which affirmed that both ORR and OER on the active surface of catalysts is irreversible and diffusion controlled. 4Ag2O‐6PrO2/γ‐Al2O3 is indicated to be proficient electro‐catalyst among other members of the series, having greater value of mass transport and diffusion coefficients. The bi‐functionality of all electrocatalysts are verified by their electrochemical responses in alkaline medium. The catalytic reduction of oxygen and oxidation of water by these electro‐catalysts imitates their potential as electrode material in batteries and unitized regenerative fuel cells (URFC) technology for energy production as substitute of platinum electrode. [ABSTRACT FROM AUTHOR]

RuO2 and PdO promoted CuO/Al2O3 mixed metal oxide nanostructures synthesized via co-impregnation technique demonstrated a robust electrocatalytic activity towards ammonia electro-oxidation (AEO). Physio-chemically characterized RuO2-CuO/Al2O3 and PdO-CuO/Al2O3 catalyst powders exhibited high electrochemical active surface area (ECSA), highest being shown by 1% RuO2-CuO/Al2O3. All fabricated electrodes displayed pleasing electroactive response towards AEO but ternary metal oxides showed superior and promoted catalytic output owing to their larger ECSA, higher current densities (j), larger diffusion coefficients (D°), greater apparent rate constants (kapp), and lower charge transfer resistance (Rct) values. Lower values of Rct obtained from EIS indicated the facilitation of electro-oxidation process over modified electrodes. The finest catalysis performance is expressed by 1% RuO2-CuO/Al2O3 producing the maximum oxidation current. All the promoted CuO/Al2O3 mixed metal oxide exhibited excellent stability and reproducibility in analyte solution. Consequently, γ-Al2O2 supported metal oxide electrocatalysts can be of great socio-economic significance by enhancing the energy production kinetics thereby achieving a higher energy output. [ABSTRACT FROM AUTHOR]