Surface‐Engineered Ti 3 C 2 T x MXene/Cu 2 O Photocathodes for Highly Selective Photoelectrocatalytic CO 2 Reduction to Ethanol

Cu 2 O is an inexpensive p‐type semiconductor that promotes the photoelectrocatalytic CO 2 reduction reaction (PEC CO 2 RR). While its low bandgap enables photoexcitation by visible light, long‐term stability remains limited due to quick charge recombination and photocorrosion. Here, we enhanced charge separation and extraction by combining Cu 2 O with surface‐engineered MXenes. In this novel architecture, TiO 2 grows in situ on the surface of Ti 3 C 2 T x and serves as a charge‐transport layer, forming a junction with Cu 2 O. On the other side, the outer TiO 2 surface exposed to the CO 2 ‐saturated electrolyte offers catalytically active sites for CO 2 reduction. Acting as a central layer, the MXene conductive backbone provides an electronically continuous pathway for electron transport. In PEC CO 2 RR, the photocathode containing 50 wt.% of MXene and a balanced amount of TiO 2 on the Ti 3 C 2 surface outperformed the best Cu/Cu x O‐based systems operating in non‐organic electrolytes reported in the literature. The FTO/Cu 2 O/ml‐Ti 3 C 2 T x ‐350‐N 2 photocathode reached 8.4 µmol cm −2 h −1 ethanol production rate and 2.74% solar‐to‐ethanol efficiency after 2 h. Moreover, pairing TiO 2 ‐MXene with Cu 2 O significantly stabilized the photocathode, which maintained 76% of the ethanol production rate after 6 h. Overall, our results establish surface‐engineered Cu 2 O/TiO 2 ‐MXene heterostructures as a solid platform for highly selective, visible‐light‐driven ethanol production with significantly improved operational stability.