Interfacial hot electron injection in Cu2O/MXene-g-C3N4 p-n heterojunction for efficient photocatalytic CO2 reduction

Photocatalytic CO2 reduction reaction (CO2RR) is a desired solution to overcome current energy and environmental problems. As a main competitive reaction, hydrogen evolution reaction (HER) urgently needs to be restrained to improve the conversion rate and selectivity of CO2RR. Here, we report a Cu2O/MXene-g-C3N4 (Cu2O/MX-CN) p-n heterojunction that achieves highly selective CO2 reduction of 93% (competing with HER) under visible light. CO is the only product of CO2RR, which yielded 28.4 μmol g−1 h−1. The introduction of Ti3C2 MXene in g-C3N4 promotes the energy of photoelectrons and the transport efficiency of photogenerated carriers at the p-n heterojunction interface via hot electron injection induced by the localized surface plasmonic resonance (LSPR) and band structure regulation. Meanwhile, apart from the component of p-n heterojunction, Cu2O also acts as the adsorption site of CO2, inhibiting HER by blocking the adsorption of protons. This study provides a novel strategy to fabricate multifunctional composite for efficient and highly selective CO2 reduction.