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

Abstract

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 μmol 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.