Electrodeposited Tin‐Antimony Alloys as Novel Electrocatalysts for Selective and Stable Carbon Dioxide Reduction to Formate

Abstract

The activity of SnSb alloy films as electrocatalysts for the CO 2 reduction reaction (CO 2 RR) to formate was presented for the first time. The effects of the film composition, electrochemical potential, and nature and concentration of the supporting electrolyte on the activity and long-term stability of these catalysts were evaluated. Sn 9 Sb 1 alloy exhibited improved longterm stability when compared to pure Sn films, and this was attributed to the lower insertion of alkali and lower formation of hydride species, inhibiting the electrode disintegration. Additionally, the Sn 9 Sb 1 film exhibited the highest faradaic efficiency (F.E.) among all prepared films, including pure Sn, reaching 96.2 % at À 1.25 V vs. RHE. This was ascribed to the better balance between the number of Sn atoms (active species) exposed on the surface and the induced morphologic effect brought by the presence of Sb, generating cube-shaped crystallites. These structures have a high number of undercoordinated surface atoms (located on the steps, corners, and kinks) and grain boundaries, resulting in more "reactive" Sn atoms, which serve as CO 2 activation sites, increasing the overall activity and F.E. for formate production.

Electrochemical Reduction of CO2 to Formate on Nanoparticulated Bi−Sn−Sb Electrodes

“…For instance, He and co-workers published a detailed review about bimetallic mixtures and the studies showed an improvement in the performance for the CO 2 reduction due to the use of these systems. [19] More recently, works have continued this topic using SnÀ PbÀ Sb alloy foil, [20,21] nanoporous CuÀ Ag alloys, [22] CuÀ Sn alloys, [23][24][25][26] SnÀ Sb alloys, [27] CuÀ Sb alloys, [28] CuÀ Bi amorphous bimetallic electrocatalysts, [29] or InÀ Sn alloy core-shell nanoparticles. [30] Tin and bismuth are the most studied metals for the CO 2 RR towards formic acid/formate and, with respect to them, recent bimetallic studies have revealed that the Bi presence improves the performance of Sn catalysts, [31,32] although pure Bi catalysts outperform those combining Sn and Bi.…”

Towards the Large-Scale Electrochemical Reduction of Carbon Dioxide

“…In addition to the above-mentioned issues, another type of poisoning phenomenon was observed in a study by Hori et al [60], where a deterioration in catalyst activity was associated with the deposition of metal impurities from the electrolyte onto the catalyst surface to form a new layer that both blocks the original active sites and provides activity towards the hydrogen evolution reaction [53,55,61]. This finding was supported by later studies that indicated the deposition of metal impurities, which may be present even in trace amounts in the electrolyte, the water source, the electrocatalyst, or the support materials [62].…”

“…In terms of catalyst design, modulating the electronic structure provides the benefits of directly adjusting the binding energies of the reaction intermediates. Thus, Zhang et al [100] described several strategies for modifying the electronic structure, including the use of alloying [87,101], single-atom catalysts [102], phase-junction catalysts [61], and surface groups [69]. Among these strategies, the alloying of several metals are particularly promising for relieving the poisoning of the catalyst by intermediates.…”

“…Among these strategies, the alloying of several metals are particularly promising for relieving the poisoning of the catalyst by intermediates. For example, the deactivation rate of Pd-based catalysts, which are known to be susceptible to CO poisoning, has been shown to be minimized when certain metals are introduced into the Pd lattice [8][9][10]61]. Thus, the strong CO-binding characteristics of Pd are lowered by incorporating a metal that has a weak affinity towards CO (usually a poor HER catalyst) [101].…”

“…In addition to minimizing catalyst poisoning by tuning the binding energy, this strategy could exert control towards the desired concentration of active species on the catalyst surface. For example, the change in morphology induced by alloying an Sn catalyst with Sb was shown to provide a balanced number of active species (Sn atoms) on the catalyst surface [61].…”