Surface Atom Regulation on Polyoxometalate Electrocatalyst for Simultaneous Low-Voltage H₂ Production and Phenol Degradation

The electrocatalytic hydrogen evolution reaction is an ideal method for H2 production. To improve the performance of polyoxometalate-based electrocatalyst in the hydrogen evolution reaction, one O2– in polyoxometalate is replaced by S2–. This weakens the binding of polyoxometalate to H*, facilitates its desorption, and improves the H2 generation property. Vulcanized polyoxometalate only requires 55 mV to achieve 10 mA·cm–2 current in the hydrogen evolution reaction. This electrocatalyst also exhibits promising performance in phenol degradation reaction, which is an ideal substitute for high-energy-consuming oxygen evolution reaction in H2 production due to low voltage to drive. To acquire 100 and 200 mA·cm–2 in the phenol degradation reaction, this vulcanized polyoxometalate only consumes 1.38 and 1.41 V. With this electrocatalyst working as a cathode and an anode simultaneously, an electrolyzer is constructed by employing phenol-containing KOH as an electrolyte. To obtain 100 and 200 mA·cm–2 current, the electrolyzer only requires 1.54 and 1.57 V. Because energy-efficient phenol degradation reaction occurs, these values are obviously lower than the oxygen evolution reaction involved in the overall water-splitting H2 production. This work provides a universal method to enhance the hydrogen evolution reaction (HER) activity of polyoxometalates. Furthermore, a new method is explored, which achieves energy conservation and phenol degradation simultaneously in H2 production.