Understanding the Single Atom Doping Effects in Oxygen Reduction with Atomically Precise Metal Nanoclusters

As a critical part of the fuel cell system, the oxygen reduction reaction (ORR) has been extensively investigated. Here we report the ORR performance catalyzed by atomically precise, heterometal-doped Ag nanoclusters (NCs). It is observed that Ag NCs with a single palladium or platinum atom doped in the kernel exhibit better ORR performance, with a similar to 100 mV lower onset potential compared with the monometallic counterpart. Density functional theory calculations demonstrate that the single-atom doping can impact the ORR performance by tuning the energy required for active-site exposure on the surface and the *OOH formation energy on the exposed active sites. We find the exposure of sulfur active sites on the surface of the NCs to be thermodynamically more feasible than the exposure of metal sites under an applied potential of -0.8 V vs Ag/AgCl. The formation energy of the *OOH intermediate on the catalytically active sites of the palladium-and platinum-doped NCs is nearly thermoneutral, which, in turn, translates to their higher catalytic activity. Overall, computational and experimental results consistently demonstrate the higher electrocatalytic activity of the doped NCs for the ORR. This study offers insights into the doping effects of atomically precise NCs