Copper-Tin Alloys for the Electrocatalytic Reduction of CO2 in an Imidazolium-Based Non-Aqueous Electrolyte

Abstract

The ability to synthesize value-added chemicals directly from CO2 will be an important technological advancement for future generations. Using solar energy to drive thermodynamically uphill electrochemical reactions allows for near carbon-neutral processes that can convert CO2 into energy-rich carbon-based fuels. Here, we report on the use of inexpensive CuSn alloys to convert CO2 into CO in an acetonitrile/imidazolium-based electrolyte. Synergistic interactions between the CuSn catalyst and the imidazolium cation enables the electrocatalytic conversion of CO2 into CO at −1.65 V versus the standard calomel electrode (SCE). This catalyst system is characterized by overpotentials for CO2 reduction that are similar to more expensive Au- and Ag-based catalysts, and also shows that the efficacy of the CO2 reduction reaction can be tuned by varying the CuSn ratio.

Electroreduction of CO2 in Ionic Liquid-Based Electrolytes

“…The IL-based electrolyte can also adsorb and stabilize CO 2 ⋅– , which is favorable for CO 2 reduction. CuSn alloys can also efficiently reduce CO 2 in an IL-based electrolyte at low overpotential 81 due to the synergistic effect between two metals.

Figure 7 The Results of Different Cu-Based Catalysts with Various IL-Based Electrolytes (A and B) X-ray photoelectron spectroscopy of (A) Cu 2p and (B) Pd 3d levels of catalysts.

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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 Sn−Pb−Sb alloy foil, [20,21] nanoporous Cu−Ag alloys, [22] Cu−Sn alloys, [23–26] Sn−Sb alloys, [27] Cu−Sb alloys, [28] Cu−Bi amorphous bimetallic electrocatalysts, [29] or In−Sn alloy core‐shell nanoparticles [30]…”

“…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.…”

Selective CO2 Reduction over Rose’s Metal in the Presence of an Imidazolium Ionic Liquid Electrolyte

“…39,40 The formation of such species has been implicated in recent studies of CO 2 RR over CuSn alloys in the presence of [BMIM] + electrolytes. 26 It is possible that the adsorption of the imidazolium-based organics serves to mitigate the inherent activity of the RM electrode and that the imidazolium and deprotonated carbene species may show a higher affinity (or binding strength) for some of the RM constituent elements than others. For example, although the extent of imidazolium/carbene adsorption has not been previously determined for electrodeposited Bi, Sn, or Pb monometallic thin films, it is possible that such species absorb more strongly to Pb.…”

“…23−25 It has also been demonstrated that CuSn alloys can promote CO 2 RR in the presence of [BMIM] + -based ionic liquids under nonaqueous conditions. 26 In this study, we build on recent work in our lab devoted to electrochemical reduction of CO 2 over post-transition metals in the presence of [BMIM] + -based electrolytes. Since prior work has demonstrated that in the presence of [Im] + electrolytes, Bi, Sn, and Pb can all promote production of CO from CO 2 , we have now worked to benchmark each of these materials under a common set of electrolyte conditions to holistically compare their CO 2 RR selectivities and activities.…”