Maximized Synergistic Interaction of Pd Single Atoms with CuCo₂S₄ Nanosheets Catalysts for High‐Efficiency Photocatalytic H₂ Production and O₂ Reduction via Enhanced Charge Separation and Transfer

Abstract The photocatalytic conversion of naturally abundant molecules into value‐added products is a key solution for sustainable development, addressing energy and environmental challenges. This study introduces a simple, eco‐friendly one‐step hydrothermal method for synthesizing atomically dispersed Pd single‐atom catalysts (SACs) on CuCo 2 S 4 semiconductor nanosheets, designed for these applications. The structure of Pd SA ‒CuCo 2 S 4 is investigated by aberration‐corrected transmission electron microscopy and X‐ray absorption fine structure (XAFS) spectroscopy. The novel synthesis process ensures strong coordination between the Pd SAs and sulfur ions on the CuCo 2 S 4 nanosheet surface, reducing overall charge transfer resistance, and making them ideal for photogenerated electron capture based on asymmetric charge density distribution. The 0.10Pd SA ‒CuCo 2 S 4 SAC (0.1 wt.% Pd loading) achieves a visible‐light‐driven H 2 production rate of 39550 µmol g ‒1 h ‒1 with a notable apparent quantum efficiency of 15.57% (at 420 nm wavelength) and high stability. The same Pd SAC can facilitate the reduction of O 2 to H 2 O 2 via photocatalytic oxygen reduction reaction (ORR), achieving an O 2 ‒to‒H 2 O 2 production rate of 19200 µmol g ‒1 h ‒1 and negligible decomposition of the produced H 2 O 2 . The proposed strategy herein offers new insights to facilitate the enhanced photocatalytic H 2 and H 2 O 2 production by Pd SAs on CuCo 2 S 4 semiconductor nanosheets by overcoming mass‐transfer limitations.