Atomic-scale insights into the dual-functional catalytic mechanism of Pd clusters on crystalline carbon nitride

Abstract

The rational design of efficient bifunctional catalysts for the oxygen evolution reaction (OER) and oxygen reduction reaction (ORR) is crucial for advancing sustainable energy conversion technologies. In this study, spin-polarized density functional theory calculations were performed to systematically investigate palladium (Pd) clusters of different sizes (n = 1–10, 13) supported on the PTI/Li+Cl− (100) surface, which is the oxidation site in experiments. Strong metal–support interactions were found to effectively stabilize Pd clusters on PTI, ensuring robust structural integrity. Free-energy analyses reveal a distinct size-dependent catalytic behavior, with Pd4@PTI exhibiting the lowest overpotentials for OER (0.41 V) and ORR (0.95 V). Further examination of scaling relations, free-energy profiles, and electronic descriptors demonstrates that the superior performance of Pd4@PTI originates from a balanced adsorption strength of oxygen intermediates, modulated by electronic interactions between Pd clusters and the PTI substrate. These findings provide fundamental insights into the size-dependent activity of Pd clusters on PTI and offer theoretical guidance for the rational design of cost-effective and durable Pd-based catalysts for clean energy applications.