Balancing H^* Adsorption/Desorption by Localized 4f Orbital Electrons of Lanthanide Dopants in Carbon-Encapsulated MoP...

MoP is one of the most efficient catalysts for hydrogen evolution reaction (HER). However, molybdenum ion exhibits a strong adsorption ability for H^* due to the abundant states in the conduction bands associated with the dispersed nature of Mo 4d electrons, which is difficult to change through interactions with other transition metal dopants of d orbital electrons. Herein, lanthanide (Ln: La, Ce, Sm, Gd, and Yb) dopants of localized 4f orbital are used to hybridize with d and p orbitals of MoP to balance the H^* adsorption energy to significantly enhance the HER activity. Density functional theory calculations indicate that the localized 4f orbital of Ln extended 4d orbital electronic density states of Mo to modulate the electron configuration near the Fermi level. Among various Ln-doped MoP with carbon-encapsulated catalysts (Ln-MoP@C) catalysts, Gd-MoP@C containing Mo 4d, C 2p, P 3p, and Gd 4f and 5d orbitals form significant states at the Fermi level, leading to the high intrinsic HER activity with low overpotentials of 74 and 134 mV at 10 mA cm^-2 in alkaline and acid electrolytes, respectively. This study provides a guiding principle for selecting dopants to tune electronic structures and enhance the intrinsic catalytic activities of transition metal catalysts through f-d-p orbital coupling.