Investigation on performance of Pd/Al ₂O ₃-C catalyst synthesized by microwave assisted polyol process for electrooxidation of formic acid

A Pd/Al ₂O ₃-C catalyst with α-Al ₂O ₃ and Vulcan XC-72 carbon black as a mixture support for direct formic acid fuel cell (DFAFC) has been prepared by a microwave-assisted polyol process for the first time. The as-prepared Pd/Al ₂O ₃-C catalysts with different mass ratios of α-Al ₂O ₃ to XC-72 carbon have been characterized by XRD, EDAX, XPS, TEM, HRTEM, and electrochemical measurements in this study. The results show that the activity of the catalyst with α-Al ₂O ₃ as the support is lower than that of the catalyst with carbon black as the support, owing to α-Al ₂O ₃ having poor electrical conductivity. However, the activity of the catalyst with α-Al ₂O ₃ and Vulcan XC-72 carbon black as a mixture support is evidently enhanced. The Pd/Al ₂O ₃-C catalyst with a mass ratio of α-Al ₂O ₃ to XC-72 carbon of 1:2 presents the narrowest particle size distribution on the surface of the mixture support, which exhibits the best activity and stability for formic acid electrooxidation among all the samples. Its current density of the positive anodic peak of formic acid electrooxidation is up to 36.97 mA cm ^-2. Pd/Al ₂O ₃-C catalyst with a suitable ratio of α-Al ₂O ₃ to XC-72 carbon shows a better catalytic activity for formic acid electrooxidation and a higher stability than Pd/C, resulting from the addition of α-Al ₂O ₃ improving its electrooxidation ability for formic acid due to an anti-corrosion property of α-Al ₂O ₃ and a metal-support interaction between the Pd nanoparticles and the α-Al ₂O ₃.