Efficient Reduction of CO₂ to CO with High Current Density Using in Situ or ex Situ Prepared Bi-Based Materials

Abstract

The development of inexpensive electrocatalysts that can promote the reduction of CO2 to CO with high selectivity, efficiency, and large current densities is an important step on the path to renewable production of liquid carbon-based fuels. While precious metals such as gold and silver have historically been the most active cathode materials for CO2 reduction, the price of these materials precludes their use on the scale required for fuel production. Bismuth, by comparison, is an affordable and environmentally benign metal that shows promise for CO2 conversion applications. In this work, we show that a bismuth–carbon monoxide evolving catalyst (Bi-CMEC) can be formed under either aqueous or nonaqueous conditions using versatile electrodeposition methods. In situ formation of this thin-film catalyst on an inexpensive carbon electrode using an organic soluble Bi3+ precursor streamlines preparation of this material and generates a robust catalyst for CO2 reduction. In the presence of appropriate imidazolium based ionic liquid promoters, the Bi-CMEC platform can selectively catalyze conversion of CO2 to CO without the need for a costly supporting electrolyte. This inexpensive system can catalyze evolution of CO with current densities as high as jCO = 25–30 mA/cm2 and attendant energy efficiencies of ΦCO ≈ 80% for the cathodic half reaction. These metrics highlight the efficiency of Bi-CMEC, since only noble metals have been previously shown to promote this fuel forming half reaction with such high energy efficiency. Moreover, the rate of CO production by Bi-CMEC ranges from approximately 0.1–0.5 mmol·cm−2·h−1 at an applied overpotential of η ≈ 250 mV for a cathode with surface area equal to 1.0 cm2. This CO evolution activity is much higher than that afforded by other non-noble metal cathode materials and distinguishes Bi-CMEC as a superior and inexpensive platform for electrochemical conversion of CO2 to fuel.

CO2 Reduction: From the Electrochemical to Photochemical Approach

“…Occasionally, formate is identified as the main reduction product on Pd as probably mediated by the surface PdH x 82. There are also a handful of reports about Zn‐, In‐, or Bi‐based materials, mostly prepared from electrodeposition, for selectively reducing CO 2 to CO 83, 84, 85, 86, 87, 88, 89. Even though Co is commonly regarded as HER‐active, partially oxidized Co ultrathin layers surprisingly reduce CO 2 to formate at a very high Faradaic efficiency 90, 91.…”

Enhanced Electrochemical Methanation of Carbon Dioxide with a Dispersible Nanoscale Copper Catalyst

“…A single-step electrochemical process that can directly convert CO 2 to methane under conditions of ambient pressure and temperature may represent an attractive alternative. Of the metals explored as catalysts for electrochemical CO 2 reduction,(8) the most active and selective identified to date are gold, silver, and bismuth, (9)(10)(11)(12)(13)(14) which produce CO as their terminal product. Copper is attractive in comparison, as it produces more reduced hydrocarbon products.…”

Cu–Sn Bimetallic Catalyst for Selective Aqueous Electroreduction of CO2 to CO

“…18 Rosenthal and co-workers have reported a generalized strategy for the electrodeposition of inexpensive electrocatalytic films from triflate salts of Bi 3+ , Sb 3+ , Sn 2+ , and Pb 2+ in organic media. [19][20][21] When the Bi-based electrodes are used for electrochemical CO 2 reduction in acetonitrile with a low overpotential of 250 mV, the 4 electrocatalysts are highly selective towards CO only when an appropriate ionic liquid is present in the system (1-ethyl-3-methylimidazolium hexafluorophosphate [EMIM]PF 6 , or 1-butyl-3-methylimidazolium hexafluorophosphate [BMIM]PF 6 , with an average 81% CO FE with [25][26][27][28][29][30] mA cm −2 ). [19][20][21] These seminal studies have thus clearly indicated that non-noble catalysts have the capability to compete with noble metals for CO 2 reduction.…”