A light-activated TiO2@In2Se3@Ag3PO4 cathode for high-performance Zn-Air batteries

Zn-air batteries (ZABs) require a small discharging voltage and large charging voltage. In this work, mesoporous hollow nanospheres of titanium dioxide@indium selenide@silver phosphate (TiO2@In2Se3@Ag3PO4) are designed and synthesized. The three-layer structure consists of TiO2 as the inner layer, In2Se3 as the middle layer, and Ag3PO4 as the outer layer. When TiO2@In2Se3@Ag3PO4 is irradiated with light, In2Se3 serves as the sensitizer to enhance light absorption and in the three-layer architecture, the photogenerated electrons and holes migrate in opposite direction in the near surface to minimize recombination. Hence, the three monomeric materials produce synergistic effects upon light illumination. The excited electrons are mainly concentrated in the conduction band (CB) of In2Se3 to promote the oxygen reduction reaction (ORR) and also increase the output voltage during discharging. On the other hand, holes are primarily concentrated in the valence band (VB) of Ag3PO4 to promote the oxygen evolution reaction (OER) and decrease the input voltage during charging. During light illumination, the discharging and charging voltages of the ZABs are 1.82 V and 0.64 V, respectively. The novel materials design reveals an effective strategy to harvest photo energy for electrochemical storage devices.