Neighboring Single Atoms Catalyst Acceleration of Hydrodehalogenation of Organic Pollutants- an Ab Intio Study

Organohalides are toxic to eco-system and human health and are increasingly found in drinking water supplies. Organohalide remediation is often achieved by hydrodehalogenation over Pd nanoparticles (Pd_nano) catalysts. Recent experimental work has found that neighboring single atom Pd catalyst surpasses the performance of Pd_nano and even isolated single atom catalysts (i-SAC) in terms of hydrodehalogenation activity and selectivity. Here, we use density functional theory calculations to develop a fundamentals understanding of the hydrodehalogenation mechanism of 4-chlorophenol on all the three catalyst. We find that the differences in behavior arises from interplay between the need to stabilize intermediates states, the configuration of accessible sites, and the ability to control bond activation. Specifically, we find that i-SAC lack the neighboring catalytic sites required for hydrodehalogenation. Nanoparticles underperform because of presence of simultaneous active bonds, increasing the probability of side reactions. The reactants also compete with solvent over nanoparticle surface for adsorption sites. n-SAC provide required neighboring catalytic sites as well as they decrease the number of active bonds, thus providing significant improvement in performance. Although this strategy has been applied to hydrodehalogenation, it can rapidly be extended to other critical water decontamination applications.