Predicted Electrocatalyst Properties on Metal Insulator MoTe₂ for Hydrogen Evolution Reaction and Oxygen Reduction Reaction Application in Fuel Cells

Abstract

Systematic spin-polarized density functional theory (DFT) calculations were executed to study the catalytic performance of the topological insulator MoTe2 (2H, 1T, and 1T′) phase. Topological insulator materials, including robust surface states and excellent carrier mobility, are suitable for oxygen reduction reaction (ORR) and hydrogen evolution reaction (HER) catalysts. Topological materials usually have a strong contribution to the density of states close to the Fermi level and high carrier mobility, which is a prerequisite for designing highly efficient catalysts. The binding energy of hydrogen (G*H) is almost zero and is a promising candidate for producing hydrogen from water. A linear scaling relationship was established depending upon the binding strengths of ORR intermediates. The limiting potential diagram could modulate the catalytic efficiency by ΔG*OH between different activity sites on MoTe2, and a volcano plot for the ORR overpotential as a function of ΔG*OH was found. According to our analysis, the best system is 1T′-MoTe2 with a γ site for the ORR and an α′ site for the HER, which are predicted to have an overpotential of 0.20 V for the HER and 0.33 V for the ORR with spin–orbit coupling calculation. HER and ORR occur along the most favorable paths on the same phase MoTe2 but at different sites, which can be considered promising candidates for both ORR and HER. Specifically, spin–orbit coupling in a metal insulator tends to interact with oxygen molecules to contribute to the ORR process, and localized electron spin coupling can guarantee the moderate binding strength of *OH intermediates. This study may provide guidance to explore new and efficient catalysts based on the theory predictions, which has been proven to be feasible for catalyst design.

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