Boosting Oxygen Electroreduction over Strained Silver

Manipulating the strain effect of Ag without any foreign metals to boost its intrinsic oxygen reduction reaction (ORR) activity is intriguing, but it remains a challenge. Herein, we developed a class of Ag-based electrocatalysts with tunable strain structures for efficient ORR via ligand-assisted competitive decomposition of Ag–organic complexes (AgOCs). Benefiting from the superior coordination capability, 4,4′-bipyridine as a ligand triggered a stronger competition with NaBH₄ for Ag ions during reduction-induced decomposition of AgOCs in comparison with the counterparts of the pyrazine ligand and the NO₃^– anion, which moderately modulated the compressive strain structure to upshift the d-band center of the catalyst and increase the electron density of Ag. Accordingly, the O₂ adsorption was obviously improved, and the stronger repulsion effect between the Ag sites and the 4e ORR product, i.e., the electron-rich OH^–, was generated to promote the desorption of OH^– via the Ag–OH bond cleavage, which enabled more Ag sites to be regenerated after ORR. Both of these led to an enhancement to the intrinsic ORR activity of the Ag-based catalyst. This competitive decomposition of metal–organic complex strategy would provide a facile method to design other catalysts with the well-tuned strain structures for energy conversion and heterocatalysis.