Abstract
The electrochemical conversion of carbon dioxide (CO2) to useful chemical fuels is a promising route toward the achievement of carbon neutral and carbon negative energy technologies. Copper (Cu)- and Cu oxide-derived surfaces are known to electrochemically convert CO2 to high-value and energy-dense products. However, the nature and stability of oxidized Cu species under reaction conditions are the subject of much debate in the literature. Herein, we present the synthesis and characterization of copper-titanate nanocatalysts, with discrete Cu-O coordination environments, for the electrochemical CO2 reduction reaction (CO2RR). We employ real-time in situ X-ray absorption spectroscopy (XAS) to monitor Cu species under neutral-pH CO2RR conditions. Combination of voltammetry and on-line electrochemical mass spectrometry with XAS results demonstrates that the titanate motif promotes the retention of oxidized Cu species under reducing conditions for extended periods, without itself possessing any CO2RR activity. Additionally, we demonstrate that the specific nature of the Cu-O environment and the size of the catalyst dictate the long-term stability of the oxidized Cu species and, subsequently, the product selectivity.
Highlights
The impacts of climate change and global warming have become a topical subject in both the political and scientific landscapes in recent times
Under CO2 reduction reaction (CO2RR) conditions, we focused on maximizing the time-resolution of the in situ XANES spectra, employing a narrower energy range for the measurements and an increased scan speed
Given the similarities in the XANES features and Linear combination fit (LCF) Cu-intercalated NTO (Cu) species composition determined under CO2RR conditions, we have drawn on the EXAFS fit results obtained in the absence of CO2 to relate the structural changes to the electrochemical activity and product distributions discussed
Summary
The impacts of climate change and global warming have become a topical subject in both the political and scientific landscapes in recent times. Copperand copper oxide-derived surfaces are the most active catalysts that can electrochemically convert CO2 to high-value and energy-dense C2 and C3 products.[8] Previous studies have demonstrated that surface geometry,[9,10] oxidation state,[11,12] particle size,[13,14] morphology,[15−17] and electrolyte composition[18,19] impact the selectivity and efficiency of the CO2RR. In situ X-ray absorption spectroscopy (XAS) was used to determine the oxidation state and local coordination environment of the copper in Cu:NTO and CuO@NTO nanoparticles under the relevant CO2RR conditions and to establish a relationship between these parameters and the product selectivity determined by on-line electrochemical mass spectrometry (OLEMS) and NMR
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