Unravelling the Bi-Functional Electrocatalytic Properties of {Mo 72 Fe 30 } Polyoxometalate Nanostructures for Overall Water Splitting Using Scanning Electrochemical Microscope and Electrochemical Gating Methods.

This study reports the use of Keplerate-type {Mo72 Fe30 } polyoxometalate (POMs) nanostructures as a bi-functional-electrocatalyst for HER and OER in an alkaline medium with a lower overpotential (135 mV for HER and 264 mV for OER), and excellent electrochemical stability. The bi-functional catalytic properties of {Mo72 Fe30 } POM are studied using a scanning electrochemical microscope (SECM) via current mapping using substrate generation and tip collection mode. Furthermore, the bipolar nature of the {Mo72 Fe30 } POM nano-electrocatalysts is studied using the electrochemical gating via simultaneous monitoring of the electrochemical (cell) and electrical ({Mo72 Fe30 } POM) signals. Next, a prototype water electrolyzer fabricated using {Mo72 Fe30 } POM electrocatalysts showed they can drive 10 mA cm-2 with a low cell voltage of 1.62 V in lab-scale test conditions. Notably, the {Mo72 Fe30 } POM electrolyzers' performance assessment based on recommended conditions for industrial aspects shows that they require a very low overpotential of 1.89 V to drive 500 mA cm-2 , highlighting their promising candidature toward clean-hydrogen production.