Strain-Engineered Rh Single Atoms on Curved WS₂ for Hydrogen Production and Coupled Photochemical Water Splitting

Hydrogen is a promising clean energy carrier, yet the high energy demand of water electrolysis limits its widespread adoption. Catalysis is crucial to enhance the efficiency of hydrogen production and lower energy costs. However, conventional catalyst design guided by the d-band theory faces inconsistencies in predicting adsorption behavior, and the oxygen evolution reaction (OER) remains a major efficiency bottleneck. To address these challenges, we developed a strain-engineered Rh single-atom catalyst anchored on curved WS₂ supported by carbon nanotubes (Rh_SA/WS₂@CNT) to modulate the electronic structure. The resultant catalyst achieves an ultralow overpotential of 17.4 mV at 10 mA cm^-2 for the hydrogen evolution reaction (HER) and a mass activity ∼65 times higher than that of commercial Pt/C. Mechanistic analysis reveals that the H* adsorption trend contradicts d-band theory predictions but is explained by orbital symmetry adaptation, where the strain-modulated d_xz orbital plays a major role in governing adsorption energetics. Beyond catalyst design, the HER catalyst was coupled with a photocatalytic iodide oxidation reaction (IOR) to replace the OER and reduce the water-splitting voltage to 0.7 V. This study not only introduces a strain-engineering strategy to optimize single-atom catalysts but also demonstrates a coupled electro-photo system that enhances energy efficiency, offering an alternative approach for sustainable hydrogen production.