Size tuning of Pt nanoparticles on ZrO2: Optimizing catalytic performance for hydrogen evolution and water-splitting reactions - A DFT study

Abstract

In heterogeneous catalysis, determining the optimal metal particle size is challenging due to the intricate relationship between particle size, electronic structure, and activity. Here, we investigate the size-dependent activity of Pt nanoparticle (PtNP)-based ZrO2 catalyst for hydrogen evolution reaction (HER) and water-splitting reaction (WSR) using density functional theory (DFT) and ab initio molecular dynamics (AIMD) simulations. By analyzing different Pt nanoparticle sizes (Pt4, Pt7, Pt11, P15, Pt19, and Pt25) supported on ZrO2, we determined their optimized geometries, and electronic structures, and calculated the hydrogen adsorption energies (ΔGH) for HER and activation energies barrier (Δ‡G) for WSR. The calculated results demonstrate that Pt11 is the optimal size for HER, exhibiting the lowest ΔGH (−0.066 eV), while Pt15 shows the lowest Δ‡G (0.24 eV) for WSR. The density of states (DOS) shows that the occupied Pt states fill the gap of ZrO2 (3.72 eV), significantly reducing the band gap (Eg) of the PtNP/ZrO2 composites. The most favorable configuration of the PtNP on ZrO2 for HER and WSR is determined to be a three-Pt-layer structure with rooflike edges which corresponds to a nanoparticle size of ∼0.70–1.55 nm for experiments. These findings can be regarded as an effort toward the design and optimization of metal-based oxide catalysts for renewable energy applications.