Elucidating the Role of Single-Atom Pd for Electrocatalytic Hydrodechlorination

In this study, we loaded Pd catalysts onto a reduced graphene oxide (rGO) support in an atomically dispersed fashion [i.e., Pd single-atom catalysts (SACs) on rGO or Pd₁/rGO] via a facile and scalable synthesis based on anchor-site and photoreduction techniques. The as-synthesized Pd₁/rGO significantly outperformed the Pd nanoparticle (Pd_nano) counterparts in the electrocatalytic hydrodechlorination of chlorinated phenols. Downsizing Pd_nano to Pd₁ leads to a substantially higher Pd atomic efficiency (14 times that of Pd_nano), remarkably reducing the cost for practical applications. The unique single-atom architecture of Pd₁ additionally affects the desorption energy of the intermediate, suppressing the catalyst poisoning by Cl^-, which is a prevalent challenge with Pd_nano. Characterization and experimental results demonstrate that the superior performance of Pd₁/rGO originates from (1) enhanced interfacial electron transfer through Pd-O bonds due to the electronic metal-support interaction and (2) increased atomic H (H*) utilization efficiency by inhibiting H₂ evolution on Pd₁. This work presents an important example of how the unique geometric and electronic structure of SACs can tune their catalytic performance toward beneficial use in environmental remediation applications.