Highly Selective H₂ Production From Photoreforming of Formic Acid Triggered by Cu Single-Atom Sites in a Cocatalyst

Photoreforming of formic acid (FA) represents a compelling technology for green hydrogen (H₂) production, but the application is limited by the relatively low activity and selectivity. Recent advancements have introduced transition-metal nitrides (TMNs) as a new class of co-catalysts for photocatalytic FA reforming, showing impressive performance but still having the disadvantage of suboptimal H₂ selectivity. Here, we present a novel Cu–W₂N₃ cocatalyst with abundant Cu single-atom sites. On combining with a CdS photocatalyst, the CdS/Cu–W₂N₃ system demonstrated an elevated H₂ generation rate of 172.69 μmol·h⁻¹ and superior H₂ selectivity in comparison to CdS/W₂N₃. Comprehensive experimental and theoretical investigations indicate that the introduction of Cu single-atom sites in Cu–W₂N₃ leads to a robust interaction with CdS, which optimizes the charge transfer. More significantly, the Cu single-atom sites modify the inert surface of the W₂N₃ cocatalyst, creating conducive electron transfer channels and leading to an abundance of active sites favorable for hydrogen evolution reaction (HER), consequently resulting in higher H₂ selectivity than pristine W₂N₃. This study provides a promising approach to achieving an efficient photoreforming reaction with specific selectivity via the design of novel cocatalysts with specialized active sites.