Bimetallic NixFe2–xP cocatalyst with tunable electronic structure for enhanced photocatalytic benzyl alcohol oxidation coupled with H2 evolution over red phosphorus

Although bimetallic phosphide cocatalysts have attracted considerable interest in photocatalysis research owing to their advantageous thermodynamic characteristics, superstable and efficient cocatalysts have rarely been produced through the modulation of their structure and composition. In this study, a series of bimetallic nickel-iron phosphide (Ni_xFe_2–xP, where 0 < x < 2) cocatalysts with controllable structures and overpotentials were designed by adjusting the atomic ratio of Ni/Fe onto nonmetallic elemental red phosphorus (RP) for the photocatalytic selective oxidation of benzyl alcohol (BA) coupled with hydrogen production. The catalysts exhibited an outstanding photocatalytic activity for benzaldehyde and a high H₂ yield. The RP regulated by bimetallic phosphide cocatalysts (Ni_xFe_2–xP) demonstrated higher photocatalytic oxidation-reduction activity than that regulated by monometallic phosphide cocatalysts (Ni₂P and Fe₂P). In particular, the RP regulated by Ni_1.25Fe_0.75P exhibited the best photocatalytic performance. In addition, experimental and theoretical calculations further illustrated that Ni_1.25Fe_0.75P, with the optimized electronic structure, possessed good electrical conductivity and provided strong adsorption and abundant active sites, thereby accelerating electron migration and lowering the reaction energy barrier of RP. This finding offers valuable insights into the rational design of highly effective cocatalysts aimed at optimizing the photocatalytic activity of composite photocatalysts.