Highly efficient photoelectrocatalytic oxidation of arsenic(iii) with a polyoxometalate-thiacalix[4]arene-based metal–organic complex-modified bismuth vanadate photoanode

Abstract

The development of highly efficient and environment friendly methods for arsenic pollution treatment has attracted special attention. Herein, a new polyoxometalate-thiacalix[4]arene-based metal–organic complex [Ag₂L(HL)][PW₁₂O₄₀]·2C₂H₅OH·2CH₃CN (1) (L = thiacalix[4]arene-based ligand) was synthesized and applied for BiVO₄ (BVO) surface modification to efficiently enhance the simulated sunlight-driven photoelectrocatalytic oxidation of arsenic(III). Compared with the pristine BVO, the removal efficiency of arsenic(III) was drastically increased to 312% at 0.6 V with the optimized 1@BVO photoanode (B1-20) versus the saturated calomel electrode (SCE) under the simulated sunlight (100 mW cm⁻²). The removal efficiency of arsenic(III) (25 mg L⁻¹) with B1-20 was up to 100% within 40 min with a faradaic efficiency of 45%. More importantly, electron spin resonance measurements and reactive species trapping experiments demonstrated that the Z-scheme heterojunction formation of 1 plays a key role in the enhanced photoelectrocatalytic performance of 1@BVO. Furthermore, density functional theory (DFT) calculations were used to investigate the relationship between the photoelectrocatalytic properties and the structure of 1. This work developed a new photoelectrocatalytic application for the polyoxometalate-thiacalix[4]arene-based metal–organic complexes by their efficient combination with BVO.