FeCo alloy@N-doped graphitized carbon as an efficient cocatalyst for enhanced photocatalytic H₂ evolution by inducing accelerated charge transfer

Cocatalysts play important roles in improving the activity and stability of most photocatalysts. It is of great significance to develop economical, efficient and stable cocatalysts. Herein, using Na₂CoFe(CN)₆ complex as precursor, a novel noble-metal-free FeCo@NGC cocatalyst (nano-FeCo alloy@N-doped graphitized carbon) is fabricated by a simple pyrolysis method. Coupling with g-C₃N₄, the optimal FeCo@NGC/g-C₃N₄ receives a boosted visible light driven photocatalytic H₂ evolution rate of 42.2 μmol h⁻¹, which is even higher than that of 1.0 wt% Pt modified g-C₃N₄ photocatalyst. Based on the results of density functional theory (DFT) calculations and practical experiment measurements, such outstanding photocatalytic performance of FeCo@NGC/g-C₃N₄ is mainly attributed to two aspects. One is the accelerated charge transfer behavior, induced by a photogenerated electrons secondary transfer performance on the surface of FeCo alloy nanoparticles. The other is related to the adjustment of H adsorption energy (approaching the standard hydrogen electrode potential) by the presence of external NGC thin layer. Both factors play key roles in the H₂ evolution reaction. Such outstanding performance highlights an enormous potential of developing noble-metal-free bimetallic nano-alloy as inexpensive and efficient cocatalysts for solar applications.