Modulating the electronic structure of ternary transition metal phosphide for enhanced hydrogen evolution activity

Rationally designing ternary transition-metal phosphides (TMPs) for the hydrogen evolution reaction (HER) is desirable but remains a significant challenge. Herein, ternary FeCoNiP encapsulated in a porous carbon shell, coupled with N-doped carbon nanotubes (FeCoNiP@NCNTs) are synthesized via a simple pyrolysis-phosphatization strategy derived from FeCoNi-MOF-100@dicyandiamide. Because Co/Ni enters the FeP lattice, FeCoNiP@NCNTs show a favorable catalytic performance towards the HER with low overpotential values of 86.7 and 233.5 mV at 10 mA cm^-2 in acidic and alkaline media, respectively, surpassing the HER performance of FeP@NCNTs, FeCoP@NCNTs, and FeNiP@NCNTs. Impressively, FeCoNiP@NCNTs display adequate acid-resistance capacity during the HER process, with nearly negligible decay due to the thin graphitized carbon shell structure with a thickness of 11.5-20.3 nm. The results of experiments, structural characterization, and density functional theory (DFT) calculations demonstrate that Co/Ni co-doping can modulate the adsorption and dissociation processes of H⁺ and downshift the d-band center of FeP. This work proposes a strategy for fabricating ternary TMP catalysts with heterogeneous structures for the HER.