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

Abstract Earth‐abundant Cu₂O 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, Cu₃(BTC)₂, as surface passivation layer is grown on Cu₂O nanorod arrays (NRARs) photocathode by in situ surface/interfacial growth. Compared to conventional Cu₂O photocathodes, the optimized Cu₂O/Cu₃(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 Cu₃(BTC)₂ layer synergistically passivates interfacial defects, forms p–n junctions at the Cu₂O/Cu₃(BTC)₂ interface, and introduces active sites catalyzing the hydrogen evolution reaction (HER), improving charge separation, transfer, and utilization efficiency. Moreover, the oxidative Cu₂O photocorrosion is inhibited owing to the accelerated charge dynamics at the Cu₂O/Cu₃(BTC)₂ interface and the hole‐scavenging ability of Cu₃(BTC)₂, meanwhile, reductive Cu₂O photocorrosion at Cu₂O/Cu₃(BTC)₂ is also attenuated by catalyzing the water reduction reaction that competes for photoelectrons and sustaining balanced “Cu²⁺(Cu⁺)/Cu⁰” cycles.