Interfacial engineering of novel inorganic-organic β-Ga2O3/COF heterojunction for accelerated charge transfer towards artificial photosynthesis

Abstract

Semiconductor-based solar-driven CO₂ to fuels has been widely reckoned as an ingenious approach to tackle energy crisis and climate change simultaneously. However, the high carrier recombination rate of the photocatalyst severely dampens their photocatalytic uses. Herein, an inorganic-organic heterojunction was constructed by in-situ growing a dioxin-linked covalent organic framework (COF) on the surface of rod-shaped β-Ga₂O₃ for solar-driven CO₂ to fuel. This novel heterojunction is featured with an ultra-narrow bandgap COF-318 (absorption edge = 760 nm), which is beneficial for fully utilizing the visible light spectrum, and a wide bandgap β-Ga₂O₃ (absorption edge = 280 nm) to directional conduct electrons from COF to reduce CO₂ without electron-hole recombination occurred. Results showed that the solar to fuels performance over β-Ga₂O₃/COF was much superb than that of COF. The optimized Ga₂O₃/COF achieved an outstanding CO evolution rate of 85.8 μmol h^-1·g^-1 without the need of any sacrificial agent or cocatalyst, which was 15.6 times more efficient than COF. Moreover, the analyses of photoluminescence electrochemical characterizations and density functional theory (DFT) calculations revealed that the fascinate construction of β-Ga₂O₃/COF heterojunction significantly favored charge separation and the directional transfer of photogenerated electrons from COF to β-Ga₂O₃ followed by CO₂. This study paves the way for developing effective COF-based semiconductor photocatalysts for solar-to-fuel conversion.

Keywords: CO(2) reduction; Covalent organic framework; Narrow-wide bandgap heterojunction; β-Ga(2)O(3).