Catalytic activity of extruded and annealed Au–Ag alloys for the electro-oxidation of CH3OH and HCOOH

Abstract

The catalytic activities of Au5-xAgx (x = 0, 1, 2 and 5) alloys for the electro-oxidation of methanol (CH3OH) and formic acid (HCOOH), together with their structure and microhardness, are studied in extruded and annealed states. For the electro-oxidation of CH3OH, the catalytic activity of Au–Ag alloys increases continually with increasing x; for HCOOH, the catalytic activity of Au–Ag alloys reaches the maximum as x = 1, indicating that the Ag addition can apparently improve the catalytic activity of Au–Ag alloys. Meanwhile, the catalytic activity of annealed Au for the electro-oxidation of CH3OH and HCOOH is lower, but that of annealed Au3Ag2 is higher than the extruded counterpart, indicating that annealing treatment has a complex effect on the catalytic activity of Au–Ag alloys. This complex effect is due to the fact that the changes of texture and twin crystal fraction of Au after annealing are different from those of Au3Ag2.