Insights into Boosting Photoelectrochemical Performance Over Cu3(BTC)2 Passivated Cu2O Nanorod Arrays

Abstract Earth‐abundant Cu 2 O is a promising photocathode material for photoelectrochemical (PEC) water splitting. However, the serious photocorrosion and low efficiency retard its practical applications. Herein, a porous Cu‐based metal–organic framework material, Cu 3 (BTC) 2 , as surface passivation layer is grown on Cu 2 O nanorod arrays (NRARs) photocathode by in situ surface/interfacial growth. Compared to conventional Cu 2 O photocathodes, the optimized Cu 2 O/Cu 3 (BTC) 2 NRARs exhibit two times higher photocurrent density, ≈2.73 mA cm −2 at 0 V RHE under visible light irradiation, and the maximum incident photon to converted electron (IPCE) performance reaches 45% (450 nm). It is demonstrated that the Cu 3 (BTC) 2 layer synergistically passivates interfacial defects, forms p–n junctions at the Cu 2 O/Cu 3 (BTC) 2 interface, and introduces active sites catalyzing the hydrogen evolution reaction (HER), improving charge separation, transfer, and utilization efficiency. Moreover, the oxidative Cu 2 O photocorrosion is inhibited owing to the accelerated charge dynamics at the Cu 2 O/Cu 3 (BTC) 2 interface and the hole‐scavenging ability of Cu 3 (BTC) 2 , meanwhile, reductive Cu 2 O photocorrosion at Cu 2 O/Cu 3 (BTC) 2 is also attenuated by catalyzing the water reduction reaction that competes for photoelectrons and sustaining balanced “Cu 2+ (Cu + )/Cu 0 ” cycles.