Enhanced mesoporous metal-support interaction through d-d orbitals hybridization for advanced hydrogen evolution catalysis

Strong metal-support interaction (SMSI) enhances catalytic activity via metal-support charge transfer but suffers from limited electronic structure regulation and imprecise control of reaction intermediate adsorption energies. This study demonstrates a systematic engineering approach by confining conductive transition metal phosphides (TMPs: FeP, CoP, Ni₂P, and MoP) within the pores of the hierarchical channels of three-dimensional ordered mesoporous carbon CMK-5. MoP was selected as the counterpart to interact with CMK-5 to induce SMSI due to its moderate reaction kinetics and optimal intrinsic catalytic activity of MoP/CMK-5. Electron-rich Co atoms (3d⁷4s²) were introduced into the composite to weaken the excessively strong hydrogen adsorption of Mo (4d⁵s¹) by adjusting the electronic structure of MoP through hybridization. The PC bond peak at 133.3 eV in X-ray Photoelectron Spectroscopy (XPS) confirmed SMSI effect between phosphide and CMK-5 substrate, while Co doping synergistically enhanced SMSI via charge redistribution. Density functional theory (DFT) analysis further revealed that CoMo hybrid could effectively regulate the d-band center position and electronic structure of MoP/CMK-5 composite by inducing charge redistribution, effectively balancing the hydrogen adsorption intensity of Mo site, thereby enhancing the SMSI effect. Moreover, the Co site (ΔG_H^⁎ = -0.125 eV) in Co-MoP/CMK-5 is close to the thermoneutral value, providing a key active site for optimizing HER (hydrogen evolution reaction) performance. Therefore, the catalyst exhibited a very low overpotential (62 mV@10 mA cm^-2) in 1 M KOH electrolyte. Benefiting from the spatial confinement effect of CMK-5 on nanoparticles, the catalytic activity shows almost no decay over 60 h.