Multi-mechanism collaborative photocatalytic CH4 conversion over Cu/ZnS/ZnOx-550 Z-scheme heterojunction

The photocatalytic conversion of CH 4 into value added liquid products in high yield has always been a huge challenge due to unavoidable peroxidation. Here, a kind of Cu/ZnS/ZnO x -550 Z type heterojunction is designed for photocatalytic CH 4 oxidation into C1 products (including CH 3 OH, CH 3 OOH and HCHO) by O 2 through the synergistic catalysis of multiple mechanisms. The CH 4 photooxidation reaction at 30 °C yields 56 mmol g −1 of C1 oxygenated products during 8 h, which exhibits a much higher value than those reported in recent studies. In situ Fourier transform infrared spectroscopy, electron spin resonance spectroscopy, X-ray photoelectron spectroscopy, electrochemical measurements and density functional calculation are used to comprehensively clarify the underlying photocatalytic mechanism. It indicates that in situ formed singlet oxygen ( 1 O 2 ) not only plays vital roles in triggering CH 4 photooxidation to C1 products, but also suppresses products peroxidation by inhibiting ·OH formation. The incorporated Cu transforms the ZnS/ZnO heterojunction from type II to Z -scheme, enhances light absorption, and, together with oxygen vacancies, regulates the electronic structure of the catalyst, thereby facilitating the adsorption and dissociation of 1 O 2 , and ultimately achieving high efficiency of CH 4 photooxidation.