Optimizing Formic Acid Electro-oxidation Performance by Restricting the Continuous Pd Sites in Pd–Sn Nanocatalysts
Tao Shen, Yun Lu, Mingxing Gong, Tonghui Zhao, Yezhou Hu, Deli Wang
Abstract
Bimetallic Pd-based electrocatalysts usually show enhanced activity toward the formic acid oxidation reaction (FAOR), while the ensemble effects on FAOR are less investigated compared with the electronic effects. Here, a series of Pd–Sn nanocatalysts with an Sn/SnOx-enriched surface are prepared via a facile method. The apparent FAOR performance is mainly determined by the inhibiting effect of tensile strains caused by lattice expansion and promoting effect of ensemble effects through restricting the continuous Pd sites. All the Pd–Sn alloys show enhanced specific activities, indicating that the ensemble effects play a main role in promoting the FAOR performance. The inhibiting effect of tensile strains results in a volcanic-type relationship between the specific activity and strains. The enhancement in stability shows a similar trend as revealed by the chronoamperometry and carbon monoxide (CO) stripping results. Both the improved FAOR activity and stability on Pd–Sn nanocatalysts could be attributed to the reason that the binding strength of adsorbed formate and CO on discontinuous Pd sites was much weaker than that on continuous Pd sites. This work suggests that restricting the continuous Pd sites through ensemble effects is an effective strategy to promote the FAOR performance of Pd-based electrocatalysts.