Boosting photoelectrochemical performance of CuFeO2/CuO photocathode by modulating heterojunction architecture and oxygen vacancies

This study aims to enhance the PEC properties of CuFeO2 nanosheets by constructing closely bonded CuFeO2/CuO heterostructures. CuO crystal-structured films were prepared using the sol-gel spin-coating method, wherein the annealing temperature was varied to modulate the content of oxygen vacancies. Compared to pristine CuFeO2 and two tandem architectures, the CuFeO2@VO-CuO core-shell architecture outperformed by yielding a photocurrent density of 68 μA/cm2, which marks an almost 8.5, 1.36 and 2.27 times enhancement. Experimental results verified solid atomic-level contact bonding at the CuFeO2@VO-CuO junction, thereby augmenting overall efficiency. Through the optimized fabrication process of the CuFeO2@VO-CuO core-shell heterostructure, carrier concentration and transport and electron-hole pair separation saw substantial improvement, further boosting its PEC performance. Critically, the presence of oxygen vacancies in the CuFeO2@VO-CuO heterostructure played a pivotal role. Oxygen vacancies eliminated potential traps for captured electrons at the interface and suppressed the formation of unoccupied interface states, reducing recombination of photogenerated electron-hole pairs. Moreover, oxygen vacancies facilitated conduction band alignment, promoting efficient separation and rapid transfer of photogenerated electron-hole pairs. In conclusion, the CuFeO2@VO-CuO core-shell heterostructure achieves efficient separation and transfer of photogenerated electron-hole pairs while effectively suppressing recombination, thanks to the synergy between the interfacial electric field and oxygen vacancies.