Enhancing photocatalytic hydrogen evolution of carbon nitride through high-valent cobalt active sites in cobalt sulfide co-catalyst

The photocatalytic hydrogen (H₂) evolution reaction driven by solar energy is one of the most promising methods to alleviate energy and environmental problems. Regrettably, the rapid recombination of photogenerated electrons and hole pairs in semiconductor catalysts leads to low solar energy conversion efficiency. To address this problem, we chose the method of co-catalyst loading. This study uses an in-situ self-assembly growth strategy to load high-valent cobalt sulfide (CoS) onto bulk carbon nitride (BCN) for photocatalytic H₂ evolution. The results show that the photocatalytic H₂ evolution performance of the optimal ratio of CoS and BCN composite (CoS-BCN(15%)) is 156 times that of BCN. The main reason for the performance improvement is that CoS nanoparticles act as co-catalysts to increase the carrier migration rate. Moreover, CoS nanoparticles contain mixed-valence Co³⁺/Co²⁺. During the reaction, high-valence cobalt ions become electron transfer stations, reacting with additional electrons to generate low-valence ions, reducing the recombination of carriers. Additionally, combined experiments and theoretical calculations show that the CoS surface is more conducive to the precipitation of H₂ than BCN. This study provides a reference for further exploring the mechanism of action of co-catalysts.