Investigation of thermodynamic stability and catalytic activity on Pt single atoms and small Pt clusters anchoring on MXene supports for the hydrogen evolution reaction

Abstract

The water electrolysis hydrogen evolution reaction (HER) is the cleanest method for hydrogen production. Platinum (Pt) is the most common HER catalyst, but its scarcity limits widespread application. Constructing catalysts by supporting metal atoms on supports effectively enhances metal utilization efficiency. In this work, we selected Ti₂CO₂ and oxygen-vacancy-containing Ti₂CO₂ (denoted as v-Ti₂CO₂) MXenes as supports, with Pt clusters of varying sizes (Pt_n, where n = 1–4) loaded on their surfaces to construct HER catalysts. Density functional theory (DFT) calculations were employed to investigate the effects of the Pt cluster size and support type on catalyst stability and catalytic performance. Our results reveal that Pt atoms supported on MXene surfaces tend to spontaneously aggregate, forming Pt clusters. Catalysts constructed with Pt clusters on Ti₂CO₂ (Pt_n/Ti₂CO₂) exhibit stronger hydrogen adsorption than those on v-Ti₂CO₂ (Pt_n/v-Ti₂CO₂). Among the cluster sizes considered, Pt₄ clusters supported on v-Ti₂CO₂ MXenes show superior catalytic performance, with the Pt₄/v-Ti₂CO₂ system achieving a Gibbs free energy (ΔG_H*) as low as 0.01 eV, which is close to zero. Electronic structure analysis indicates that charge transfer in Pt₄/v-Ti₂CO₂ primarily occurs between Pt and H atoms, whereas in Pt₃/v-Ti₂CO₂, the involvement of support oxygen leads to strong interactions among H, Pt, and O, resulting in stronger hydrogen adsorption. The presence of oxygen vacancies weakens this adsorption. Therefore, tuning the size of the supported Pt clusters and engineering substrate defects leverages metal–support interactions to modulate HER catalytic performance, providing a strategy for designing novel HER catalysts.