In-situ construction of metallic Ni₃C@Ni core–shell cocatalysts over g-C₃N₄ nanosheets for shell-thickness-dependent photocatalytic H₂ production

Herein, we designed the shell-thickness-controlled Ni₃C@Ni/g-C₃N₄ photocatalysts with intimate Schottky-junctions by an in situ high-temperature transformation strategy. Meanwhile, we found that the cocatalysts with optimized Ni shell-layer thickness of 15 nm could achieve the best visible-light photocatalytic H₂-production performance of 11.28 μmolh⁻¹, with an apparent quantum yield (AQY) of 1.49 % at 420 nm, which was 16 times higher than that of Ni₃C/g-C₃N₄. Moreover, an excellent stability is achieved. The well-defined density functional theory (DFT) calculations indicate that the “TOP_C1” sites of Ni₃C@Ni can exhibit the H adsorption and Gibbs free energies of -0.07eV and 0.18 eV, respectively, which should be hydrogen-evolution active sites instead of two “HOLLOW” sites. Interestingly, the intimate Schottky-junctions, could hinder rapid charge recombination, increase reactive sites, boost catalytic kinetics and passivate unstable surface of Ni₃C, thus achieving shell-thickness-dependent hydrogen evolution. Therefore, the Ni₃C@Ni core–shell cocatalysts will open a new avenue for robust solar fuel production.