An integrated photocatalytic redox architecture for simultaneous overall conversion of CO2 and H2O toward CH4 and H2O2

Abstract

Solar-driven overall conversion of CO2 and H2O into fuels and chemicals shows an ultimate strategy for carbon neutrality yet remains a huge challenge. Herein, an integrated photocatalytic redox architecture of Zn NPs/GaN Nanowires (NWs)/Si is explored for light-driven overall conversion of CO2 and H2O into CH4 and H2O2 simultaneously without any external sacrificial agents and additives. The as-designed architecture affords a benchmark CH4 activity of 189 mmol gcat−1 h−1 with a high selectivity of 93.6%, in the synchronized formation of H2O2 at a considerable rate of 25 m g−1 h−1. Moreover, a considerable turnover number of 27,280 mol CH4 per mol Zn was achieved over a long-term operation of 80 h. By operando spectroscopic characterizations, isotope experiments, and density functional theory calculations, it is unraveled that Zn sites are synergetic with GaN to drive CO2-to-CH4 conversion with a lowered energy barrier of 0.27 eV while inhibiting hydrogen evolution reaction with a relatively high energy barrier of 0.93 eV. Notably, owing to the unique surface properties of GaN, water is split into *OH and *H, followed by the formation of H2O2 because of the alleviated adsorption strength of *OH by Zn NPs. Together, the hierarchical architecture enables the achievement of high activity and high selectivity of CH4 from CO2 reduction in distilled water along with the generation of H2O2. This work provides an integrated photocatalytic redox architecture for the synchronized production of CH4 and H2O2 with the only inputs of CO2, distilled water, and light.