Surface co-modification with highly-dispersed Mn & Cu oxides of g-C3N4 nanosheets for efficiently photocatalytic reduction of CO2 to CO and CH4

In this work, an in-situ way has been developed to achieve the co-modification of highly-dispersed Mn and Cu oxides to g-C3N4 nanosheets for efficient CO2 reduction. The Mn & Cu amount-optimized nanosheets exhibit the improved photocatalytic activity for CO2 reduction to CO and CH4 both by 3 times compared with the generally-bulk g-C3N4, mainly attributed to the nanosheet structure and to the roles of modified Mn and Cu oxides. Based on the transient-state surface photovoltage responses, transient-state photoluminescence spectra, and electrochemical measurements, it is confirmed that the modified Mn and Cu oxides could respectively capture the photogenerated holes and electrons, and provide the catalytic functions for water oxidation and CO2 reduction. Remarkably, the simultaneous introduction of Mn and Cu oxides shows an obvious synergistic effect on the improvement of photocatalytic activity for CO2 reduction. This work provides a feasible way to synthesize high-activity g-C3N4-based photocatalysts for energy production.