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

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 Rh-2 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 Rh-2 diatomic pairs, while the N-vacancies induce a stable 3N/Rh-Rh/1N2C coordination between the carrier and Rh-2 diatomic pairs. The local charges on the support framework with N vacancies tend to be transferred to Rh-2 diatomic site by 3N/Rh-Rh/1N2C bridge, which made the charge enriched Rh-2 diatomic site become the active center of reaction, enhance charge separation efficiency of Rh-2/HCNS-Nv. Compared with Rh-1 SAC, further Density Functional Theory (DFT) calculation confirms that Rh-2 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%.