Polyoxometalated metal-organic framework superstructure for stable water oxidation
Kaihang Yue, Ruihu Lu, Mingbin Gao, Fei Song, Yao Dai, Chenfeng Xia, Bingbao Mei, Hongliang Dong, Ruijuan Qi, Daliang Zhang, Jiangwei Zhang, Ziyun Wang, Fuqiang Huang, Bao Yu Xia, Ya Yan
Abstract
Stable, nonprecious catalysts are vital for large-scale alkaline water electrolysis. Here, we report a grafted superstructure, MOF@POM, formed by self-assembling a metal-organic framework (MOF) with polyoxometalate (POM). In situ electrochemical transformation converts MOF into active metal (oxy)hydroxides to produce a catalyst with a low overpotential of 178 millivolts at 10 milliamperes per square centimeter in alkaline electrolyte. An anion exchange membrane water electrolyzer incorporating this catalyst achieves 3 amperes per square centimeter at 1.78 volts at 80°C and stable operation at 2 amperes per square centimeter for 5140 hours at room temperature. In situ electrochemical spectroscopy and theoretical studies reveal that the synergistic interactions between metal atoms create a fast electron-transfer channel from catalytic iron and cobalt sites, nickel, and tungsten in the polyoxometalate to the electrode, stabilizing the metal sites and preventing dissolution.