Tuning charge transfer process of MoS2 photoanode for enhanced photoelectrochemical conversion of ammonia in water into gaseous nitrogen

Abstract

Charge transfer efficiency of semiconductor photoanode in photoelectrochemical (PEC) system is one of crucial factor determining the overall PEC performance. Previously, we have developed a MoS2-based PEC system that is able to specifically convert ammonia nitrogen in aqueous solution into gaseous nitrogen (e.g. N2) utilizing oxysulfur radicals. Herein, in order to solve the slow charge transfer issue of reported MoS2-based PEC oxidation system, we further improve the PEC conversion efficiency by tuning composition of MoS2/WS2 nanosheets heterojunction photoanode. The hybrid MoS2/WS2(1:1) electrode displays the highest PEC performance and ammonia conversion efficiency compared to the individual MoS2 or WS2 constituent under visible light irradiation, which can be mainly ascribed to the reduced electrode resistance and improved charge transfer efficiency according to the physiochemical, electrochemical and spectroscopic analysis. The results prove that both interfacial and interior charge carrier transfer processes of photoanode are crucial and tailorable in order to efficiently generate reactive radical species for ammonia conversion.