Quantum Chemical Study on the Adsorption of Formic Acid on a Pt-Sn(111)/C Alloy Surface

Density functional theory (DFT) and self-consistent periodic calculations were used to investigate the adsorption of formic acid (HCOOH) and carbon monoxide (CO) at eight sites, such as top, bridge, hcp and fcc, on a Pt-Sn(111)/C surface. The vibrational frequency, electric charge, energy band and density of states of HCOOH before and after adsorption on a Pt-Sn(111)/C surface were determined. The results show that before doping, the favored adsorption site for HCOOH and CO is the fcc-Pt-3 site. After doping the surface with Sn, the Fermi level moves to the right, the conduction band broadens, and the valence and conduction bands lower slightly. The change of the electronic structure on Pt-Sn(111)/C promotes both the adsorption and dissociation of HCOOH, which can improve the performance of anode catalysts for direct formic acid fuel cells (DFAFCs). Based on the anti-poisoning analysis of the catalyst surface, it was also found that the adsorption energy of CO on Pt-Sn(111)/C surfaces is lower than that on Pt(111)/C ones. The results show that the adsorption energy of CO on Pt-Sn(111)/C decreases through two ways, and the anti-poisoning ability of the catalyst towards CO is improved after doping with Sn.