Optimizing Formic Acid Electro-oxidation Performance by Restricting the Continuous Pd Sites in Pd–Sn Nanocatalysts

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/SnO x -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.

Phase-Controlled Synthesis of Pd–Sn Nanocrystal Catalysts of Defined Size and Shape

“…Taken together, we assign the Pd 3 Sn sample to the disordered, random alloy Fm m phase although the intermetallic phase cannot be ruled out given the low intensity of the superlattice peaks. Similar challenges in phase assignment are evident in prior reports of Pd 3 Sn NPs. , …”

Improvement of electrocatalytic alcohol oxidation by tuning the phase structure of atomically ordered intermetallic Pd-Sn nanowire networks

“…As shown in Fig. 3d and Figs S1, S2, the mapping of Pd-Sn OICs demonstrates that both Pd and Sn distribute homogeneously through the whole i-NNWs [47].…”

“…(1) introducing Sn atoms with relatively large atomic radius (140 pm) into Pd atoms (137 pm) to form specific OICs would result in a strain effect [47]. When Sn atoms are not introduced, the interatomic Pd-Pd distance in the Pd with fcc structure (lattice parameter a = b = c = 3.889 Å) is 2.75 Å [22].…”

Twinned and Single-Crystal Palladium Nanocrystals for the Electrooxidation of HCOOH

“…3,6 Both Pt-and Pd-based nanomaterials have been widely investigated as catalysts for the formic acid oxidation reaction (FAOR), and Pd-based nanomaterials exhibited larger potential to be used commercially than Pt-based nanomaterials because of their higher resistance to CO poisoning than the latter ones. 1,7,8 It has been reported that the electrocatalytic activity of Pd catalysts toward the oxidation of HCOOH is structure-sensitive. 9,10 By studying the single-crystal plane, Hoshi et al reported that in HClO 4 the catalytic activities showed the order as Pd (110) < Pd (111) < Pd (100), and similar results were also reported by other researchers.…”

“…The direct formic acid (HCOOH) fuel cell is an important type of low-temperature fuel cell and has attracted much attention. − When it works, HCOOH oxidizes in the anode while an oxygen reduction reaction happens in the cathode. , Both Pt- and Pd-based nanomaterials have been widely investigated as catalysts for the formic acid oxidation reaction (FAOR), and Pd-based nanomaterials exhibited larger potential to be used commercially than Pt-based nanomaterials because of their higher resistance to CO poisoning than the latter ones. ,, It has been reported that the electrocatalytic activity of Pd catalysts toward the oxidation of HCOOH is structure-sensitive. , By studying the single-crystal plane, Hoshi et al reported that in HClO 4 the catalytic activities showed the order as Pd (110) < Pd (111) < Pd (100), and similar results were also reported by other researchers. , Because the commercial catalysts for direct HCOOH fuel cells are nanoscale, the shape-controlled synthesis of Pd-based nanocatalysts with specific crystalline shape could make a bridge between theory and application.…”