Unravelling the Bi‐Functional Electrocatalytic Properties of {Mo72Fe30} Polyoxometalate Nanostructures for Overall Water Splitting Using Scanning Electrochemical Microscope and Electrochemical Gating Methods

Abstract

Abstract This study reports the use of Keplerate‐type {Mo72Fe30} 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 {Mo72Fe30} 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 {Mo72Fe30} POM nano‐electrocatalysts is studied using the electrochemical gating via simultaneous monitoring of the electrochemical (cell) and electrical ({Mo72Fe30} POM) signals. Next, a prototype water electrolyzer fabricated using {Mo72Fe30} 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 {Mo72Fe30} 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.

Keywords

• electrochemical gating
• electrochemical water splitting
• industrial alkaline electrolyzer
• polyoxometalates
• scanning electrochemical microscope (SECM)