No abstract

Zn‐air batteriesare a perspective power source for grid‐storage. But, after they are discharged at1.1 to 1.2 V, large overpotential is required for their charging (usually 2.5 V). This is due to a sluggish oxygen evolution reaction (OER). Incorporating organic pollutants into the cathode electrolyte is a feasible strategy for lowering the required charging potential. In the discharge process, the related oxygen reduction reaction, hydrophobic electrocatalysts are more popular than hydrophilic ones. Here, a hydrophobic bifunctional polyoxometalate electrocatalyst is synthesized by precise structural design. It shows excellent activities in both bisphenol A degradation and oxygen reduction reactions. In bisphenol A containing electrolyte, to achieve 100 mA ⋅ cm−2, its potential is only 1.32 V, which is 0.34 V lower than oxygen evolution reaction. In the oxygen reduction reaction, this electrocatalyst follows the four‐electron mechanism. In both bisphenol A degradation and oxygen reduction reactions, it shows excellent stability. With this electrocatalyst as cathode material and bisphenol A containing KOH as electrolyte, a Zn‐air battery was assembled. When “charged” at 85 mA ⋅ cm−2, it only requires 1.98 V. Peak power density of this Zn‐air battery reaches 120.5 mW ⋅ cm−2. More importantly, in the “charge” process, bisphenol A is degraded, which achieves energy saving and pollutant removal simultaneously in one Zn‐air battery.

As a H2O2 generator, a 2e− oxygen reduction reaction active electrocatalyst plays an important role in the advanced oxidation process to degrade organic pollutants in sewage. To enhance the tendency of NiCo2S4 towards the 2e− reduction reaction, N atoms are doped in its structure and replace S2−. The result implies that this weakens the interaction between NiCo2S4 and OOH*, suppresses O−O bond breaking and enhances H2O2 selectivity. This electrocatalyst also shows photothermal effect. Under photothermal heating, H2O2 produced by the oxidation reduction reaction can decompose and releaseOH, which degrades organic pollutants through the advanced oxidation process. Photothermal effect induced by the advance oxidation process shows obvious advantages over the traditional Fenton reaction, such as wide pH adaptation scope and low secondary pollutant due to its Fe2+ free character. With Zn as anode and the electrocatalyst as cathode material, a Zn−O2 battery is assembled. It achieves electricity generation and photothermal effect induced by the advance oxidation process simultaneously.