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 g_cat⁻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.