Sandwich‐Type Polyoxometalate Mediates Cobalt Diselenide for Hydrogen Evolution in Acidic Electrolyte

Abstract Ease of tunability of the redox properties of polyoxometalates (POMs) has made this class of inorganic molecular oxides most attractive for electrocatalytic applications. However, the design of inexpensive transition‐metal oxides for the hydrogen evolution reaction (HER) is a big challenge owing to their insufficient catalytic efficiency and durability at high proton concentrations. Firm linkage of an electroactive POM on the surface of cobalt diselenide nanobelts (CoSe₂−NBs) is expected to overcome the issue of stability due to their strong coordination chemistry. Subsequent synergy due to the redox active nature of stabilized POMs facilitates proton‐coupled electron transfer (PCET), which could improve HER activity at higher proton concentrations. Herein, a nanocomposite of a sandwich‐type POM and CoSe₂−NBs shows, as predicted, enhanced HER activity in acid with an overpotential of 187 mV at 10 mA cm⁻², as well as marked long‐term electrochemical stability. This work offers a route to introduce POMs into a catalyst system to facilitate PCET for boosted electrocatalysis.