Insights into the efficient charge separation and transfer efficiency of La, Cr-codoped SrTiO3 modified with CoP as a noble-metal-free co-catalyst for superior visible-light driven photocatalytic hydrogen generation

The exploration of non-noble-metal-based photocatalysts with high efficiency and durability toward hydrogen evolution is vitally necessary to meet the challenges of the global energy and environmental crisis. In this work, we prepared noble-metal-free cobalt phosphide (CoP) as an efficient co-catalyst on La, Cr-codoped SrTiO3 (La, Cr: SrTiO3) to form a novel photocatalyst with enhanced H2 evolution activity. It was evidenced that the introduction of CoP led to a remarkable improvement in the photocatalytic H2 evolution activity of La, Cr: SrTiO3, and the content of CoP in the composite had an important influence on the photocatalytic activity. The optimized La, Cr: SrTiO3/CoP (4 wt%) composite exhibited a catalytic H2 evolution rate of 198.4 mu mol h-1 g-1, which was nearly 27 and 15 times higher than that of La, Cr: SrTiO3 and CoP, even slightly higher than that of La, Cr: SrTiO3/Pt (0.5 wt%). More importantly, this novel photocatalyst also showed a long-term stability without noticeable activity degradation. Based on the results of UV-vis diffuse reflectance spectroscopy, photoluminescence spectra, photocurrent response, and electrochemical impedance spectra, we ascribed the enhanced H2 evolution performance of the La, Cr: SrTiO3/CoP to a synergistic effect including the broadened visible-light response range, accelerated photogenerated charge separation and transfer efficiency. It is believed that our present work throws light on the rational design of novel, high-performance, visible-light-driven hybrid photocatalysts based on non-noble-metal elements.