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.