Tuning the Composition of Electrodeposited Bimetallic Tin–Lead Catalysts for Enhanced Activity and Durability in Carbon Dioxide Electroreduction to Formate

Abstract

Bimetallic Sn-Pb catalysts with five different Sn/Pb atomic ratios were electrodeposited on Teflonated carbon paper and non-Teflonated carbon cloth using both fluoroborate- and oxide-containing deposition media to produce catalysts for the electrochemical reduction of CO (ERC) to formate (HCOO ). The interaction between catalyst composition, morphology, substrate, and deposition media was investigated by using cyclic voltammetry and constant potential electrolysis at -2.0 V versus Ag/AgCl for 2 h in 0.5 m KHCO . The catalysts were analyzed before and after electrolysis by using SEM and XRD to determine the mechanisms of Faradaic efficiency loss and degradation. Catalysts that are mainly Sn with 15-35 at % Pb generated Faradaic efficiencies up to 95 % with a stable performance. However, pure Sn catalysts showed high initial stage formate production rates but experienced an extensive (up to 30 %) decrease of the Faradaic efficiency. The XRD results demonstrated the presence of polycrystalline SnO after electrolysis using Sn-Pb catalysts with 35 at % Pb and its absence in the case of pure Sn. It is proposed that the presence of Pb (15-35 at %) in mainly Sn catalysts stabilized SnO , which is responsible for the enhanced Faradaic efficiency and catalytic durability in the ERC.

Leaded Bronze Alloy as a Catalyst for the Electroreduction of CO2

“…Among the post transition metals (Hg, Cd, Pb, Tl, In, Sn, and Bi) with high hydrogen overpotential and negligible CO adsorption to reduce selectively CO 2 to formate in aqueous medium, lead appears to be the most straightforward and suitable cathode material for technical applications, since it combines the high‐overpotential for the parasitic hydrogen evolution reaction (HER) with lower toxicity than cadmium and mercury ,. Bimetallic metal alloys have also been applied to CO 2 RR aiming at boosting formate production due to synergistic interactions between two transition metals, or a transition metal and copper . Recently, we investigated leaded bronze as a novel cathode material for a variety of electro‐organic reactions that features the catalytic performance of lead but exhibits a higher mechanical and chemical stability .…”

“…The respective efficiencies are FE H2 ∼60 % and FE CO < 5%. Note that the missing contribution to reach 100 % total efficiency might be ascribed to the sluggish reduction of metastable tin and/or lead oxides at such low potentials ,,. Upon increase of the applied cathodic potentials, the overall efficiency of the HER decreases to a quasi‐steady value around 40 %, that one of CO slightly increases and remains relatively constant without exceeding 10 % and the one of formate increases steeply and remains in the 50‐60 % range in the potential window from −1.0 to −1.2 V. A very minor selectivity for methane is found at highest applied potentials (max FE CH4 =2.6 % at −1.17 V).…”

“…We rationalize the product selectivity of mechanically polished CuSn 7 Pb 15 electrocatalyst for CO 2 RR as follows: considering that the active surface is constituted by two well distinct phases (a Pb‐rich almost Cu‐free Pb/Sn phase and a Cu‐rich Cu/Sn phase) and that the typical products formed on them do not decompose on each other, we expect a cathode product selectivity composed of a mixture of their typical product distributions. The main chemical produced by either pristine Pb or PbSn alloys upon CO 2 RR in aqueous medium is HCOO − usually exceeding the amount of evolved H 2 from the parasitic HER in a wide potential range ,,,,,. On the other hand, the catalytic properties of the Cu‐rich Cu/Sn phase could be dominated either by its major component, by the overall alloy ensemble or by a combination of both.…”

Electrochemical reduction of CO2 on Pb–Bi–Sn metal mixtures: importance of eutectics

“…Though the majority of the work is on coinage metals such as alloys of Cu with Au [14,15], Ag [16,17], Ni, Sn and Pb [18], Ag-In [19], W-Au [20] and Pd-Pt [21]. Relatively, alloys of Pb, Sn, and Bi have received less attention for example Pb-Sn [22][23][24][25], Sn-In [26]. Therefore, it can be considered well established that alloying of metals enhances catalytic activity in several cases.…”

Scanning electrochemical microscopy screening of CO2 electroreduction activities and product selectivities of catalyst arrays

“…One of the most promising catalysts for this process is Sn/SnO 2 , which has shown high selectivity and low overpotential for CO2RF 3,4 . The adsorption and surface interaction of the radical anion CO 2 •− is a key step in the reaction mechanism influencing the overall reaction rate [5][6][7][8][9][10][11][12] . The nature of the catalytic active sites can include an active, nascent, Sn surface formed in situ by oxide reduction and the oxide itself 12 .…”