Density Functional Theory Study of Nanostructured Pd-C4N/XMoY (X, Y = S, Se, Te) Heterostructures for Oxygen Reduction, Oxygen Evolution, and Hydrogen Evolution Reactions

Seeking efficient, stable, and inexpensive electrocatalysts applied to water splitting and fuel cells in acidic media is still challenging for the development of renewable energy. Herein, we propose a single atom catalyst based on heterojunction composed of Pd-C4N and XMoY (X, Y = S, Se, Te), and conduct a detailed exploration of its oxygen reduction reaction (ORR), oxygen reduction reaction (OER), and hydrogen evolution reaction (HER) catalytic performance using density functional theory methods. First, all Pd-C4N/XMoY is proven to have good stability by calculating binding energy. Then, the ORR/OER electrocatalytic behavior of Pd-C4N/XMoY is investigated, and the potential-determining step of most catalysts for ORR is *OH reduction, while for the OER, it is *OH to *O. Additionally, all catalysts exhibit good catalytic activity for the ORR/OER, but only five have better catalytic activity than Pt(111). In particular, Pd-C4N/SMoSe exhibits a negligible potential barrier for the HER (-0.004 V). Pd-C4N/SeMoTe presents immense trifunctional activities toward ORR/OER/HER with overpotentials of 0.32/0.28/-0.02 V. The electronic structure analysis proves that the high activity is attributed to the good conductivity of the material itself and the adjustable binding ability of the *OH. Our report contributes to comprehending and designing more efficient single-atom catalysts to meet the demand for multifunctional catalysts.