CO₂‐reduction, catalyzed by metal electrodes

Abstract

The electrochemical reduction of CO 2 proceeds in aqueous electrolytes with large overpotential, since the first step of the CO 2 reduction, i.e., CO 2 − anion radical formation, requires highly negative potential. The product distribution from the CO 2 reduction depends greatly on the electrode metal. Cu yields CH 4 , C 2 H 4 and alcohols; Au, Ag and Zn give CO as the main product; Pb, Hg, In, Sn, Cd and Tl form HCOO − ; Ni, Fe and Pt do not reduce CO 2 whereas H 2 evolves from the electrolysis of H 2 O. The reason is rationalized in terms of the adsorption of CO 2 − anion radical on the electrode metals. The CO 2 reduction at the single crystal electrodes of Cu and Pt metals is summarized, and the mechanism of the hydrocarbon formation at Cu electrode is discussed in detail. The rate of CO 2 reduction is enhanced by increased transport of CO 2 to the electrode; such as the solid polymer electrolytes, the gas diffusion electrodes, the electrolyses under high pressure or in nonaqueous electrolytes.

Carbon Solving Carbon's Problems: Recent Progress of Nanostructured Carbon‐Based Catalysts for the Electrochemical Reduction of CO2

“…[18,19] These metals can be separated into three distinct groups: formic acid producing metals (Sn, Hg, Pb, Bi), CO producing metals (Au, Ag and Zn) and Cu in its own group due to its ability to produce a range of higher order hydrocarbons. [5,20] However, these metal electrocatalysts face many issues; primarily poor selectivity, loss of efficiency toward competing hydrogen evolution, poor stability and inactivation by CO. [10] For the CO 2 RR and other processes, carbon based electrocatalysts and supports have shown to be very stable and efficient in operation. [13,16,21,22] Whether applied as totally metal free or as carbon-metal composites, development of cost effective carbon based material with equal or better activity to precious metal benchmarks could potentially realise energy storage/conversion devices for mainstream applications.…”

“…[15,42] Reducing CO 2 electrochemically proceeds quite simply from a thermodynamic standpoint with standard electrode potentials toward aqueous reduction products (pH 7) referenced to NHE shown in Reaction (1) and (4) - (8). [5,8] …”

“…Much of the criticism regarding renewable energy points to issues of intermittency and baseload power capability, aspects that advanced conversion and storage technologies can address. [5] However, the relatively high cost and low energy densities of current energy conversion/storage devices greatly hinders their commercial integration into renewable energy systems. A long proposed method of energy conversion and storage is through the CO 2 reduction reaction (CO 2 RR) into useful molecules such as: methane, formic acid, carbon monoxide (CO) etc.…”

Carbon-Supported Fe Catalysts forCO2Electroreduction to High-Added Value Products: A DEMS Study: Effect of the Functionalization of the Support

“…In recent years, different metallic electrodes have been studied for the electrochemical reduction of carbon dioxide, since the product distribution strongly depends on the used material, surface metallic arrangement, and surface energy [11][12][13][14][15][16][17]. Copper has been found to be one of the most effective electrode materials for the CO 2 reduction process at atmospheric pressure and room temperature in aqueous solutions [11,12,16].…”

“…Copper has been found to be one of the most effective electrode materials for the CO 2 reduction process at atmospheric pressure and room temperature in aqueous solutions [11,12,16]. On the other hand, CO 2 is hardly reduced on group VIII-X metal electrodes such as Fe, Co, and Ni, under similar conditions [15][16][17].…”