Electroreduction of dissolved carbon dioxide on roughened copper and molybdenum microdisk electrodes [EMBARGOED]

Abstract

The increasing levels of carbon dioxide (CO2) in the atmosphere and its consequent impact on climate change have necessitated the exploration of new solutions to mitigate its effects. The current methods such as spectroscopic and chromatographic techniques that are used to determine the concentration of CO2 have their own disadvantages such as high cost, tedious, and time consuming. Electrochemical sensors have a high potential due to its portability, precision, stability, and accuracy. However, there is a need to find alternative electrode materials since the conventional materials are relatively expensive and may be susceptible to chloride ions attack. This study investigates the electrochemical behaviour of dissolved CO2 on roughened copper (Cu) and molybdenum (Mo) microdisk electrodes, which were mechanically polished using silicon carbide papers. To date, there is no groups that have reported the electrochemical behaviour of CO2 on roughened Mo and Cu microdisk electrodes prepared via this approach. This could be because researchers may have disregarded this pretreatment step to prioritize the search for alternative materials capable of demonstrating high electrocatalytic efficiency in CO2 reduction. X-ray diffraction spectra confirm the absence of any contamination or presence of abrasive materials on the electrode surface. These findings show that the roughened electrodes exhibit a significantly higher electrocatalytic activity than the smoothened electrodes for the reduction of dissolved CO2. Unfortunately, the roughened Cu microdisk electrodes may experience dissolution and redeposition processes in the presence of chloride ions when cycling at around 0 V vs. saturated colomel electrode (SCE) which could complicate the interpretation of the electrochemical results pertinent to the reduction of CO¬2. The roughened Mo microdisk electrodes exhibit a diffusion-controlled electrochemical reaction as a linear relationship was observed between the current and square root of scan rate. Furthermore, this work demonstrates that saturating the electrolyte solution with CO2 using a bubbling time of just 20 minutes at a flow rate of 5 L min-1 for a 50 mL solution is sufficient based on the voltammograms after bubbling for different period of time. This study provides new insights into the electrochemical behaviour of dissolved CO2 on roughened Mo microdisk electrodes and highlights their potential as a promising material for CO2 reduction and other electrochemical applications. Roughened Cu microdisk electrodes may also be used but in the absence of chloride ions. Ultimately, this work contributes to the ongoing efforts to mitigate the effects of climate change and move towards a sustainable future.