Enhancing carbon dioxide gas-diffusion electrolysis by creating a hydrophobic catalyst microenvironment

Abstract

Electroreduction of carbon dioxide (CO2) over copper-based catalysts provides an attractive approach for sustainable fuel production. While efforts are focused on developing catalytic materials, it is also critical to understand and control the microenvironment around catalytic sites, which can mediate the transport of reaction species and influence reaction pathways. Here, we show that a hydrophobic microenvironment can significantly enhance CO2 gas-diffusion electrolysis. For proof-of-concept, we use commercial copper nanoparticles and disperse hydrophobic polytetrafluoroethylene (PTFE) nanoparticles inside the catalyst layer. Consequently, the PTFE-added electrode achieves a greatly improved activity and Faradaic efficiency for CO2 reduction, with a partial current density >250 mA cm−2 and a single-pass conversion of 14% at moderate potentials, which are around twice that of a regular electrode without added PTFE. The improvement is attributed to a balanced gas/liquid microenvironment that reduces the diffusion layer thickness, accelerates CO2 mass transport, and increases CO2 local concentration for the electrolysis.

Recent Progresses in Electrochemical Carbon Dioxide Reduction on Copper‐Based Catalysts toward Multicarbon Products

“…[ 225 ] For example, the flow channel and diffusion layer, which are usually ignored in most lab‐based studies, can constitute different cells and affect the mass transfer as well as improve the energy efficiency when they are applied in a real electrolyzer. [ 224 ] In this section, we will mainly introduce three aspects of cell engineering, that is, electrode, electrolyte, and cell design, toward the efficient conversion of CO 2 to value‐added C 2+ products.…”

“…Hydrophilic/hydrophobic properties of the electrode have also attracted much attention in regulating the CO 2 RR performance, especially in a flow cell. [ 224,233,234 ] Adjusting the hydrophilic/hydrophobic properties of electrodes can tune the triple‐phase reaction interface, CO 2 mass transfer efficiency, and the adsorption state of intermediates. [ 235 ] Recently, De Arquer et al.…”

Electrochemical Reduction of CO2 to CO on Hydrophobic Zn Foam Rod in a Microchannel Electrochemical Reactor

“…When the potential was below −1.7 V (vs. SCE), FE CO of zinc foam began to decrease, but the hydrophobic zinc foam still maintained relatively stable at high potential. The hydrophobic zinc foam improved the selectivity of CO as it can facilitate the transport of CO 2 gas to the catalyst layer through the gas phase, reduce the distance of the liquid electrolyte required for the diffusion of CO 2 gas to the catalyst layer, which accelerated the transport of CO 2 to the catalyst and increased the steady concentration of CO 2 near the catalyst [27]. The decreased selectivity of CO on zinc foam electrode at high potential may be ascribed to the insufficient supply of CO 2 .…”

“…To verify this guess, we compared the electrochemically active surface area (ECSA) of zinc foam and hydrophobic zinc foam. The ECSA and the electrochemical double-layer capacitance is in proportion, which represents the area of an electrode that is wetted and accessible to the electrolyte [27] and can be measured by cyclic voltammetry (CV) [29]. The experiment was carried out in the N 2 -saturated 0.1 M KHCO 3 electrolyte solution.…”

Surface Microenvironment Optimization Induced Robust Oxygen Reduction for Neutral Zinc-Air Batteries

“…Optimal microenvironment could realize the enrichment of intermediates across the electrolyte/electrode interface and further promote the interfacial chemical potential-gradient. With satisfied chemical potential-gradient, the intermediate energy states or even the reaction pathways can be tailored, which will decrease the reaction energy barrier and promote the reaction kinetics 21,22 . However, most of current work were focused on elevating the intrinsic activity of catalytic sites, yet there still lacks effective strategy to optimize the surface microenvironment around active sites 23,24 .…”