Bifunctional Electrocatalysts for Oxygen Reduction and Borohydride Oxidation Reactions Using Ag₃Sn Nanointermetallic...

Incorporating an oxophilic metal into a noble metal to produce a cost-effective Ag₃Sn nanointermetallic catalyst is an emerging approach to enhance the catalytic activity of monometallic Ag in fuel cells, which is different from previous notions that consider a transition metal to increase the catalytic activity of Pt. The Ag₃Sn electrocatalyst is prepared by a facile electrodeposition method and exhibits high catalytic performance for the oxygen reduction reaction (ORR) and borohydride oxidation reaction (BOR). The Ag₃Sn electrocatalyst has an ORR specific activity of 0.246 mA cm^-2, 1.3 times greater than the value of commercial Pt/C (0.187 mA cm^-2) and a long-term stability with an 11 mV decrement in the half-wave potential and 7.01% loss of the diffusion-limiting current density after 2000 cycles, superior to that of Pt/C. Moreover, the Ag₃Sn electrocatalyst delivers a surprisingly higher BOR current density of 11.332 mA cm^-2 than most bimetallic Ag alloys. The better ORR catalytic activities of Ag-based alloys may arise from the ensemble effect, in which Sn atoms may promote the oxygen adsorption and Ag atoms may contribute to the removal of reaction products.