Synergistic effect of spatially isolated Ni2P and NiO redox cocatalysts on g-C3N4 for sustainably boosted CO2 photocatalytic reduction

Severe recombination of photogenerated carriers and low reaction rates have been recognized as the main obstacles of graphitic carbon nitride (g-C3N4, CN) in CO2 photocatalytic reduction. In this work, spatially isolated Ni2P and NiO redox cocatalysts were synchronously introduced on CN via the facile one-step gas-solid phosphating reaction between Ni(OH)(2)/CN and Na2HPO2 center dot 2H(2)O, and the spatial distribution and mass ratio of Ni2P and NiO could be optimized by adjusting the phosphating degree. Excitingly, the optimal sample Ni2P/NiO/CN(0.25) delivered remarkably enhanced CO and CH4 production of 12.05 and 2.32 mu mol g(-1) under 8 h visible-light irradiation, respectively being 5 and 30 times that of CN, even superior to that of CN modified with atomically dispersed Pd. Mechanism analysis revealed that NiO could act as the hole acceptor via forming p-n heterojunctions with CN, favoring the water oxidation half-reactions, while Ni2P could serve as the electron sink, facilitating CO2 adsorption and activation, as well as the CO2 reduction half-reactions. Due to the synergistic effect of Ni2P and NiO, the separation and transfer of photogenerated carriers were greatly accelerated, and the CO2 photocatalytic reduction rates of CN were dramatically boosted. Furthermore, the in situ formed Ni-0 during photocatalytic reactions endowed the resulting catalyst with sustainably efficient CO2 photocatalytic reduction activity. In sum, this work demonstrated the effectiveness and feasibility of spatially isolated redox cocatalyst-decoration in promoting CO2 photocatalytic conversion. It is believed that the mechanism proposed here will encourage more rational construction of advanced photocatalysts for targeted reactions.

Automated summary

In this work, spatially isolated Ni2P and NiO redox cocatalysts were synchronously introduced on CN, significantly enhancing the CO2 photocatalytic reduction rate. The optimal sample delivered a 12.05 μmol g(-1) CO production and a 2.32 μmol g(-1) CH4 production, which were 5 and 30 times that of CN, even superior to that of CN modified with atomically dispersed Pd. The synergistic effect of Ni2P and NiO greatly accelerated the separation and transfer of photogenerated carriers, boosting the CO2 photocatalytic reduction rates of CN.