A Win–Win Strategy to Fabricate Double Z-Scheme Self-Supporting Integrated Photoelectrode Derived from Aniline Wastewater for Synthesis of H₂O₂ and Recovery of Polyaniline

H2O2 and polyaniline (PANI) are important chemicals in the chemical and manufacturing industries. Herein, the concept of “turning waste into treasure” was proposed: PANI derived from aniline (ANI) wastewater was used to fabricate a double Z-scheme NiFe2O4–Ov@CdS@PANI photoelectrocatalytic catalyst for alleviating environmental pollution and producing H2O2. The double Z-scheme self-supporting integrated photoelectrode enables high light utilization and an excellent redox ability. In addition, the further designed Janus “floating” photocathode can efficiently entrap O2 from the air and afford unidirectional transportation of O2 from the gas-collecting side to the catalyst side during the O2 reduction reaction. The H2O2 yield obtained using the Janus “floating” photocathode (264.52 mg·L–1·h–1) is 7.2 times higher than those of conventional “submerged” electrodes. By coupling the ANI polymerization reaction with the H2O2 production, the assembled electrolyzer exhibits a low cell voltage of 1.3 V vs Ag/AgCl to drive the integrated two half-reactions, the recovery rate of ANI reaches 96.5%, and the yield of H2O2 reached 41.9 mg·L–1 (1.3 V vs Ag/AgCl) in solution with ANI, nearly 3 times the yield in solution without ANI.