Engineering oxygen vacancies of cobalt tungstate nanoparticles enable efficient water splitting in alkaline medium

By Luo, Fang; Xu, Ruizhi; Ma, Shuangxiu; Zhang, Quan; Hu, Hao; Qu, Kongang; Xiao, Shenglin; Yang, Zehui; Cai, Weiwei
Published in Applied Catalysis B: Environmental 2019

Abstract

Development of earth-abundant, efficient and stable electrocatalysts for water splitting is of crucial importance for environmentally friendly energy conversion and storage. Here, we report an oxygen deficient cobalt tungstate nanoparticles with diameter of 8 nm (CoWO4-x@C) as efficient bifunctional electrocatalyst for hydrogen evolution reaction (HER) and oxygen reduction reaction (OER), which exhibits comparable HER activity to commercial Pt/C with overpotentials of 32.5 mV and 46.8 mV vs. RHE to deliver current density of 10 mA cm?2 in acidic and alkaline mediums, respectively, ascribed to the rich oxygen vacancies facilitating the hydrogen adsorption and its relative recombination, respectively. Additionally, undetectable degradation is observed for CoWO4-x@C after 10,000 potential cycles indicating high durability. Meanwhile, CoWO4-x@C requires only 295 mV overpotential to deliver 10 mA cm?2 in the OER test, which is better than the benchmarking IrO2 (313 mV). 1.57 V comparably lower than Pt/C-IrO2 (1.59 V) is required for achieving the water splitting current density of 10 mA cm?2 without any degradation for 12 h.

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