The synergy of in situ -generated Ni 0 and Ni 2 P to enhance CO adsorption and protonation for selective CH 4 production from photocatalytic CO 2 reduction

The selective photocatalytic reduction of CO 2 to CH 4 remains a challenge because there is a need for not only strong adsorption sites for the intermediates, but also optimal proton-feeding sites on the photocatalyst surface. Herein, a synergistic dual-site function between in situ -generated Ni 0 and Ni 2 P on carbon nitride nanosheets (CN) for photocatalytic reduction of CO 2 to CH 4 is presented. The highest CH 4 production rate of 69.03 μmol g −1 h −1 is achieved on Ni 2 P/CN-0.5 in an aqueous suspension. Detailed analyses show that the promotion of CH 4 is closely correlated with the formation of Ni 0 sites due to light irradiation, which is confirmed by tracking the compositions of Ni 2 P/CN-0.5 through XPS and HRTEM characterization. Density functional theory calculations have been combined with CO-TPD and in situ FTIR spectra to reveal the synergy between in situ -generated Ni 0 sites and Ni 2 P. It shows that the Ni 0 sites can stabilize the key intermediate *CO, while the Ni 0 –Ni 2 P interface can promote *H transfer from Ni 2 P to Ni 0 . Therefore, the CO intermediates are rapidly protonated to form CHO* instead of being desorbed from the surface to produce CO, and subsequently CHO* will be converted into CH 4 . This work demonstrates a new strategy of designing highly efficient photocatalysts with synergistic catalytic sites for CO 2 conversion to hydrocarbons.