p-Block Tin Single-Atom Catalysts with Tuned p-Orbital State for Oxygen Reduction Reaction

Single-atomic p-block main-group metal catalysts have garnered increasing attention for oxygen reduction reaction (ORR) in previous studies. However, their catalytic performance is not sufficiently satisfactory, as the electronic structure of p-block metals is difficult to regulate to enable them to have appropriate adsorption free energy for the intermediate species of ORR. Herein, a Sn-N-GDY catalyst was synthesized under the guidance of density functional theory (DFT) calculations. As an innovative active site, Sn is bonded to two pyrrolic N, with two sp-N in close proximity to them. Both pyrrolic N and sp-N diminish the Sn 5p states, which reduces the adsorption energy of Sn toward ORR intermediates. Experimentally, the Sn single-atom catalyst (SAC) is prepared with an anhydrous method to mitigate the agglomeration tendency of tin. The as-synthesized Sn-N-GDY achieves a half-wave potential (E_1/2) of 0.86 V in alkaline electrolyte for ORR and exhibits exceptional cycling stability in zinc-air batteries, operating 1,147 h at 2 mA cm^-2. With better performance than most main-group ORR catalysts, this material shows excellent application potential. This work establishes a new paradigm for main-group SACs on GDY and offers a design strategy for highly efficient non-precious metal SACs.