Investigating In Situ Corrosion Dynamics During CO₂ Reduction Using Inductively-Coupled Plasma Mass Spectrometry

There is a critical need to develop new technologies for the sustainable production of carbon-based fuels and chemicals. The electrochemical CO₂ reduction reaction (CO₂RR) provides a path to meet this need, offering opportunities to use renewable electricity to drive the conversion of CO₂ into products such as ethylene, ethanol, and methane. A challenge limiting the implementation of CO₂RR is catalyst stability during reduction. Greater fundamental understanding is needed to uncover the governing physical and chemical factors as well as mechanisms of degradation in CO₂RR operating conditions. Catalysts of interest for CO₂RR include Ag and Au, but one particularly interesting catalyst is Cu, as it can form C₂₊products. Changes to the Cu surface morphology can favor the formation of certain products.<br/><br/>The goal of this research is to quantify dynamic corrosion of Cu CO₂RR electrocatalysts. Specifically, we aim to probe the relationship between degradation rate and catalyst morphology changes and applied potential. Cu electrocatalyst degradation in CO₂RR conditions was examined in varying electrolyte pH, gas environments to isolate the effects of hydrogen evolution and CO₂RR, and potentiostatic conditions in Faradaic and non-Faradaic regions to determine the effect of catalysis. Atomic force microscopy (AFM) was used to characterize the electrode surface pre- and post- electrolysis by distinguishing nanostructures on the electrode surface and calculating surface roughness, which was found to be dependent on applied potential. While AFM allows for examination of the resulting morphology of electrode surfaces due to various experimental conditions, the use of inductively coupled plasma mass spectrometry (ICP-MS) enables on-line studies for quantifying catalyst degradation. Using a flow cell allows for simultaneous application of a potential and/or current density while sending electrolyte effluent to the ICP-MS to detect corroded catalyst species in trace amounts (low ppb level), coupling the examination of reaction and corrosion kinetics. On-line ICP-MS data indicates that during CO₂ reduction in potassium bicarbonate electrolyte, Cu degrades at negative applied potentials. Greater fundamental understanding of Cu morphology changes and degradation during CO₂RR conditions can help to steer selectivity towards desired products and improve catalyst performance. The use of on-line ICP-MS studies accelerates corrosion studies by enabling real-time measurements during reaction conditions. Elucidating the factors that drive catalyst degradation enables the assessment of the lifetime and long-term stability of electrocatalytic devices.