Particle Size and Morphology of Carbon Dioxide Reduction Electrocatalysts Fabricated By Pulse/Pulse-Reverse Electrodeposition

A variety of techniques for management of carbon dioxide emissions from power generation facilities and other industrial sites have been under active investigation for decades, in an effort to mitigate the environmental impacts of these releases. Once such approach is electrochemical reduction, which treats the waste CO 2 as a source material for the production of value-added materials. Currently, the most promising form factor for this electrocatalytic application appears to be a stack-based system, where catalyst is immobilized on porous media that is interfaced with a liquid or solid electrolyte, and the reactant carbon dioxide is delivered to the active region by gaseous diffusion, which is orders of magnitude faster that diffusion though aqueous media. Various carbonaceous reduction products can be created depending on the composition, size, and microstructure of the catalyst particles, including formic acid/formate, carbon monoxide, alcohols, and hydrocarbons. In general, smaller catalyst particles, ideally in the nanoparticulate (« 1 μm) range, tend to yield superior catalytic performance, due to a combination of factors such as a higher density of exposed grain boundaries and a higher fraction of exposed crystalline facets that are uncommon in particles of micron size or larger. This talk will survey recent work illustrating the ability of pulse/pulse-reverse electrodeposition processes to tune the size of particles applied to gas-diffusion electrode substrates, with a primary focus on two single-metal catalyst materials relevant to carbon dioxide electroreduction: tin and copper. The former is a catalyst primarily for formic acid production, while the latter is unique among single-metal catalysts as the only element known to date to produce significant amounts of hydrocarbons and/or alcohols. Particle morphology and representative particle size will be discussed as a function of pulsed electrodeposition waveform parameters, with the goal of highlighting overarching trends across the waveform space.