Investigation of novel Cu-based catalysts for selective CO2 reduction on gas diffusion electrodes

Abstract

The increasing global warming since the last couple of decades necessitates a shift to renewable energy sources. CO2 reduction (CO2R) to energy dense products driven by renewable electricity can be a long-term solution to close the carbon cycle. The CO2 reduction reaction (CO2RR) being a kinetically sluggish reaction, requires an active catalyst for efficient conversion. The utilised catalysts for CO2RR can be evaluated in terms of activity, selectivity as well as stability. Cu is the only known element so far which produces a huge spectrum of hydrocarbon products. To begin with, this thesis reports the investigation of Cu-PTFE systems and the selectivity change with varying PTFE amounts in modified gas diffusion electrodes, showing a tilt towards C-C coupled products. Cu-PTFE composite with 50 wt. % PTFE was found to be more selective towards ethylene than other compositions. A later part of this study showed a selectivity change with increasing molar ratios of Cu-CuI composite. It was observed that the addition of CuI drives the selectivity of CO2RR in the direction of more C2+ products. The 1:4 ratio of Cu-CuI was found to be the most selective towards C2+ products with ~ 30 % ethanol at current densities of -150 mA/cm2 . Selected Cu based High Entropy Alloy catalysts were synthesized using a new “aerosol capture technique” and were tested for CO2RR in the same electrode setup as the previous electrodes. The online gas chromatography (GC) results showed abundance of H2. At the end of the thesis, after evaluation of the experimental results, future solutions for optimisation of the catalyst modified electrodes are briefly discussed.