Synergistic Optimization of Morphology and Vacancies on Diatomic Rhodium Catalysts Dispersed on Carbon Nitride for Efficient Photocatalytic Reduction of CO₂

Abstract Diatomic site catalysts (DAC) have better performance with higher metal content and more flexible active sites compared with single atomic site catalysts (SAC). Herein, the authors for the first time achieved Rh₂ DAC on loose porous g‐C₃N₄ hollow nanospheres with N‐vacancies and applied to photocatalytic CO₂ reduction reaction, overcoming the current limitations of the low electron–hole recombination rate and prolong the lifetime of the photogenerated carrier. The high specific surface area of hollow nanosphere facilitates the uniform dispersion and anchoring of Rh₂ diatomic pairs, while the N‐vacancies induce a stable 3N/Rh‐Rh/1N2C coordination between the carrier and Rh₂ diatomic pairs. The local charges on the support framework with N vacancies tend to be transferred to Rh₂ diatomic site by 3N/Rh‐Rh/1N2C bridge, which made the charge enriched Rh₂ diatomic site become the active center of reaction, enhance charge separation efficiency of Rh₂/HCNS‐Nv. Compared with Rh₁ SAC, further Density Functional Theory (DFT) calculation confirms that Rh₂ DAC can effectively stabilize rate‐limiting intermediates CHO^*, and well weaken the C─O bond strength in CH₃O^* species, promote the generation and separation of CH₄, resulting in high CO₂ reduction efficiency and CH₄ electron selectivity of up to 91.65%.