Platinum Atoms Dynamics on the Surface of Hexagonal Boron Nitride Containing Vacancy Defects.

Single-atom catalysts (SACs) have transformed the field of heterogeneous catalysis by enabling efficient utilization of metal atoms and enhancing the selectivity and activity of chemical reactions. The propensity of metal atoms to aggregate into nanoclusters complicates the consistent production of SACs and creates challenges in understanding their interactions with naturally defected supports. Based on the example of platinum SACs on hexagonal boron nitride, this study combines ab initio computational methods with kinetic nucleation model to propose a route to controlled fabrication of SACs through defect engineering. It shows that diffusion barriers obtained for an isolated SAC on pristine surface do not represent realistic growth conditions and highlights the importance of accounting for collective atomic behavior when modeling nucleation and growth processes. The study extends the classical Volmer-Weber mechanism of nanocluster growth to account also for the presence of surface vacancy defects and predicts the values of the single atom-to-nanocluster ratio as a function of the surface defect density and platinum loading. The effect of ambient oxygen on platinum SACs formation has been examined to investigate its role in hindering metal interactions with defects and promoting clustering.