The promotional effect of Ag in activated carbon supported Pt-Ag nanoalloy electrocatalyst towards alkaline ethanol oxidation reaction: A kinetic study

Due to the scarcity of fossil fuels and their severe environmental consequences, the development of high efficiency energy conversion devices such as fuel cells (FCs) has gained considerable attention. The specific energy conversion efficiency of FC is highly influenced by the activity of the electrocatalysts. Platinum (Pt) is widely used as an electrocatalyst due to its high activity and stability, but high cost and depletion of resources hinder its commercialization. One of the workable strategies for the practical application of Pt is to reduce its content by alloying with non-precious metals and simultaneously maintain its electrochemical performance. In this context, we developed a low Pt-loaded Pt-Ag/AC alloy electrocatalyst. The electrocatalytic activity and kinetics of the as-synthesized catalyst were evaluated by cyclic voltammetry (CV), chronoamperometry (CA), and electrochemical impedance spectroscopy (EIS) using the three-electrode electrochemical workstation at room temperature. The electrocatalytic investigations reveal that the resultant AC-supported Pt-Ag with Pt: Ag = 1.8:2.3 at% has higher activity i.e., 32.7 mA cm-2 as compared to that of Pt/AC (20.8 mA cm-2) in an alkaline electrolyte and makes it an efficient electrocatalyst for the electro-oxidation of ethanol. The electron donation from Ag to Pt during the alloying process helps in weakening the interaction with CO and other intermediate species, thereby lowering their binding and poisoning effect on the surface, which may partly be responsible for the improved catalytic performance of Pt-Ag/AC. The activated carbon (AC) support also favors charge transport by reducing ohmic resistance. The cyclic stability studies also reveal that Pt-Ag/AC performs significantly better than Pt/AC with a current retention of 65.2 % and 48.3 % till 1000 cycles, respectively. Therefore, alloying Pt with earth-abundant Ag under rational composition provides optimized surface and electronic properties that result in improved ethanol electro-oxidation activity while reducing the utilization of precious noble metals.