The EDX result shows that the Au−Ag atomic ratio is 23.87/76.13 in AuAg3.2 NSs, which is wellconsistent with the feeding ratio of Au and Ag metal precursors (Figure S2). Furthermore, the widely tunable composition of the bimetallic Au−Ag NSs can be facilely achieved through simply altering the mole ratios of the initial metal precursors (Figure S3 and Table S1). It should be noted that the precise control on the composition of our catalysts via the one-pot synthetic strategy is more outstanding compared with other previously reported Au−Ag NPs.