Polyoxometalated metal-organic framework superstructure for stable water oxidation

Stable non-precious 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 with a low overpotential of 178 millivolts at 10 milliamperes per square centimeter. An anion exchange membrane water electrolyzer incorporating this catalyst achieves 3 amperes per square centimeter at 1.78 volts at 80 degrees Celsius and stable operation at 2 amperes per square centimeter for 5,140 hours at room temperature. In-situ electrochemical spectroscopy and theoretical studies revealed 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.