Tuning the texture of high-surface area copper electrodes to enhance the product selectivity in the electrocatalytic CO2 reduction

One of the biggest challenges of our society is to decrease carbon emissions while the worldwide energy demand keeps steadily increasing. An attractive solution to decrease the impact of the ongoing climate change is to utilize the otherwise unwanted and emitted CO₂ as raw material for the electrocatalytic conversion to valuable chemicals and fuels (CO₂RR). In this way electric energy is stored in the form of chemical bonds.

An interesting CO₂RR electrocatalyst is copper, since it shows high electrocatalytic activity for the CO₂ reduction to more valuable hydrocarbons (beyond C1-products), such as ethanol or ethylene. To improve the activity and selectivity of catalysts many research efforts are directed towards nanostructured high-surface area materials. At imec we are currently testing high surface area and porous interconnected metal nanowire nanomesh electrodes based on copper. To obtain copper nanomesh electrodes we electrochemically deposit copper in a 3D-porous anodic aluminum oxide (AAO) template resulting in a polycrystalline surface texture. When applying this copper nanomesh electrodes in the aqueous CO₂RR we obtain a mixture of CO, CH₄ and C₂H₄ as products. A known strategy to tune the product selectivity is to control the copper surface texture and it was found that with (111) Cu CH₄ and with (100) Cu C₂H₄ are mainly obtained.

In this master thesis, the student will study how to obtain a preferential surface texture on copper nanomesh electrodes to increase the CO₂RR product selectivity. Different strategies will be experimentally explored such as influence of post-deposition annealing procedures, the effect of the plating bath composition & deposition conditions and/or the influence of the underlying substrate to tune the surface texture. The obtained copper nanomeshes will then be structurally characterized with special attention given to the crystal orientation. Finally, the student will test the preferentially oriented copper electrodes in an electrochemical cell for their activity towards the reduction of CO₂ and quantify the products formed. The entire experimental work of the project is carried out in the electrochemistry labs at imec.