Multiple chemical valences induced interface regulation in perovskite nickelate/carbon nitride for boosting photocatalytic hydrogen evolution.

Recent developments in transition metal-based photocatalysts have heightened the need for superior solar utilization. Evidence suggests that properly adjusting the chemical valence of the transition metal elements could simultaneously achieve broad-spectrum absorption and efficient charge separation for the photocatalysts. However, the understanding and application of this strategy remain a significant challenge. Herein, a series of LaNiCoO/g-CN (LNCO/CN) composites were synthesized employing a mild reduction procedure in the HAr atmosphere. Experimental studies reveal that the composites regulated by interfacial coordination unsaturation Ni and metal Ni possess accelerated Z-scheme charge transfer through the interfacial bond between Ni and N. Besides, the localized-surface-plasmon-resonance-induced "hot electrons" injection process of in situ grown Ni nanoparticle is confirmed, which can efficiently quench the photoinduced holes and create hole vacancies around the interface. Due to the synergistic effect between Ni and Ni, the lifetime of the photo-excited electrons is prolonged with inhibited recombination behavior. After modulation, optimal LNCO/CN Z-scheme hybrid exhibits 9-fold promotion of photocatalytic hydrogen evolution rate compared to pristine LNCO/CN. This study gives valuable insight into the purposeful utilization of the chemical valence modulating strategy, which alters the chemical valence of transition metal elements to enhance the performance of perovskite-based photocatalysts dramatically.