Dual active sites modified polymeric carbon nitride for efficient photocatalytic CO₂ reduction and H₂ evolution

Rational design of dual active sites for polymeric carbon nitride (PCN) photocatalysts to regulate the separation and migration rates of photoexcited charge pairs represents an advanced strategy for the green development of CO₂ and H₂ production. Herein, ethyl alcohol groups modified PCN with enriched N vacancies (EG-CN) was prepared by the solvothermal method with different concentrations of reducing ethylene glycol (EG). All EG-CN samples exhibit boosted photocatalytic CO₂ reduction activity than PCN. Among them, 50EG-CN sample (treated with a ratio of 50 to 10 of ethylene glycol to deionized water) exerts outstanding evolution rate of CO and CH₄, reaching 16.3 μmol g^-1·h^-1 and 0.8 μmol g^-1·h^-1, which were 3.3 and 2 times that of the reference PCN, respectively. As a universal test, photocatalytic H₂ evolution further proofs that EG-CN samples have an enhanced catalytic performance. The H₂ evolution efficiency on 50EG-CN is nearly twice compared to PCN. Experimental results and theoretic calculations reveal that the synergistic effect of the dual active sites not only optimizes the surface electronic properties but also serves as new sites for the activation and reaction of molecules. This work supposes the conversion process of the intermediates, reveals the enhanced photocatalytic mechanism for CO₂ reduction, and provides constructive guidance for designing multiple active sites on PCN-based materials to enhance the photocatalytic performance.