Predicting Catalytic Efficiency of Nickel Nanoclusters: A Surface Activity Parameter Based Approach for Water Splitting

Nickel nanoclusters are crucial catalysts in numerous organic and inorganic reactions. In this study, we theoretically investigate the water-splitting reaction on pristine nickel nanoclusters of varying sizes. We introduce a novel metric, the Surface Activity Parameter (SAP), to systematically assess the catalytic activity of nanoclusters. Our findings reveal that adsorption energy and activation energy for the water-splitting reaction exhibit a size-dependent trend. Specifically, as cluster size increases, adsorption energy becomes more negative, stabilizing the reactant molecules more effectively, while activation energy shows an increasing trend. The relationship between SAP and adsorption energy suggests an inverse correlation, indicating that smaller clusters exhibit higher catalytic efficiency. Furthermore, our analysis shows that the variation in SAP follows an exponential decay with increasing cluster size, demonstrating a predictable trend in catalytic behavior. The study also examines molecular interactions such as bond length elongation, vibrational frequency shifts, and Ni-O bonding characteristics post-adsorption, providing a mechanistic insight into the catalytic activity of nickel nanoclusters. The insights gained from this study could facilitate the rational design of efficient nanocatalysts for water-splitting applications.