Role of Binder in Cu₂O Gas Diffusion Electrodes for CO₂ Reduction to C₂₊ Products

Abstract

The electrochemical CO 2 reduction reaction (CO 2 RR) to form C 2+ products was investigated to obtain high selectivity in liquid CO 2 -fed systems having the limitation of low current density. Over the past decade, flow cells with gas diffusion electrodes (GDEs) have emerged to achieve high current densities close to the industrial-relevance scale by overcoming gas diffusion limitations. However, key parameters of GDE design, including binders, were not sufficiently identified to enhance selectivity and current density for C 2+ products. Nafion, FAA-3, and polypyrrole were used to explore the effects of binder type and content on GDE properties such as porosity (gas permeability), ion conductivity, and electron conductivity for the modulation of the CO 2 RR on the Cu 2 O catalyst. The Cu 2 O GDEs with high binder content showed poor selectivity for C 2+ products because of their low exposure to the catalyst surface and decreased gas permeability. The anion exchange ionomer, FAA-3, showed high selectivity for C 2+ products and electrode stability resulting from the C−C coupling increase and suppression of the hydrogen evolution reaction, which was induced by OH − conductivity. In contrast, the cation exchange ionomer, Nafion, exhibited low electrode stability due to the loss of gas products through the catholyte and due to its excessive wettability.

Recent Advances in Electrochemical, Photochemical, and Photoelectrochemical Reduction of CO2 to C2+ Products

“…After all, to accurately produce the required product, it is essential to conduct research that considers the material and type of the substrate, the type of the binder, the type of the reactor, the operating conditions of the reactor, and the supply type of the reactant. [140][141][142] The reaction pathway for a specific C 2+ product must be manipulated by controlling the above properties. However, the complex reaction mechanism of the CO 2 ECRR has not been identified because of insufficient reaction intermediate products after the formation of CC coupling (*CO*CHO intermediate).…”

Ce4+-Doped CuO Mesoporous Nanosheets for CO2 Electroreduction to C2H6 with High Selectivity under a Wide Potential Window in a Flow Cell

“…As *CO adsorption energy in Cu-based catalysts is monotonically increased with the copper oxidation state, Cu 2+ species can be directly designed as catalysts to advance the C–C coupling toward C 2 product generation. − However, Cu 2+ species may be reduced to Cu 0 under CO 2 ER conditions, leading to the degradation of activity and durability of CO 2 ER. , Heteroatom doping can introduce new active sites and protect the valence states of Cu species through energy level hybridization with the d-band center of the original Cu-based catalyst, modulating the adsorption behaviors of the intermediates and directing the CO 2 ER pathway toward a desired C 2 product. ,, Therefore, constructing the CuO nanostructure by Ce doping can be expected to regulate the adsorption strengths of the intermediates for maneuvering C–C coupling and the hydrogenation process toward the conversion of CO 2 ER to C 2 H 6 . Recently, a gas diffusion electrode (GDE)-equipped flow-cell electrolyzer has been engineered for CO 2 ER to the desired products at commercially relevant current densities by circumventing the mass transport limitation of CO 2 , , where the gas diffusion electrode (GDE) in a flow cell should be highly hydrophobic and porous to promote CO 2 diffusion and prevent flooding. , In this study, Ce 4+ -doped CuO mesoporous nanosheets are designed for CO 2 ER to C 2 H 6 in a flow cell. Ce 4+ doping induces oxygen vacancies and modulates the electron distribution of CuO, which increases the electron density of Cu sites near Ce 4+ sites and oxygen vacancies, ensuring adequate coverage of a *CO intermediate to promote C–C coupling, while the electron-deficient Cu sites away from Ce 4+ sites and oxygen vacancies strengthen the interaction with the CH 3 CH 2 O* intermediate, favoring its further conversion to C 2 H 6 .…”

Fractal growth of a fern-like nanostructured Cu2O film electrode for electrochemical reduction of CO2 to ethanol

“…Their study revealed that an increase in the potentials and phosphate ion concentration promoted the branched-3D growth which gave maximum efficiency towards ECO 2 R. 35 Moreover, the choice of the surface chosen for electrodeposition is also an important factor that can determine the size, structure and morphology of the deposited material for electrocatalytic applications. 23,35,40 So far, many electrodeposited materials on the surfaces of Cu foil, Cu disc, PANI, Toray sheets with a gas diffusion electrode, Ni-foam and FTO 33,[41][42][43][44][45] have been reported for the application of ECO 2 R, but electrodeposition of nanostructured Cu 2 O on stainless steel (SS-316) has not been explored for ECO 2 R, even though a copper layer can be deposited rmly on SS-316. Stainless steel is known to be stable, durable, less corrosive and a good electrical conductor which can be used as an electrode and current collector in electrochemical energy storage and conversion systems.…”