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.