An in situ near-ambient pressure X-ray photoelectron spectroscopy study of CO 2 reduction at Cu in a SOE cell

Abstract

The cathodic behavior of a model solid oxide electrolysis cell (SOEC) has been studied by means of nearambient pressure (NAP) X-ray Photoelectron Spectroscopy (XPS) and near edge X-ray absorption fine structure (NEXAFS), aiming at shedding light on the specific role of the metallic component in a class of cermets used as electrodes. The focus is on the surface chemistry and catalytic role of Cu, the increasingly popular metallic component in electrodes used in CO 2 electrolysis and CO 2 /H 2 O co-electrolysis. The NAP-XPS and NEXAFS results, obtained in situ and operando conditions and under electrochemical control have provided important insights about the evolution of the Cu surface chemical composition. We have found that in dry CO 2 ambient carbon deposits are scavenged at low cathodic potential by the oxidising action of nascent O, while at high cathodic polarisations C grows due to activation of the CO reduction. Instead, in CO 2 /H 2 O mixtures, surface deposit of C is steady over the whole investigated potential range. The presence of adsorbed CO has also been detected during electrolysis of CO 2 /H 2 O mixtures, while no CO is found in pure CO 2 ambient.

In Situ Characterization for Boosting Electrocatalytic Carbon Dioxide Reduction

“…In addition to liquid electrolytes, the electrolytic behavior of solid oxide is often studied by near-ambient pressure XPS to detect reaction intermediates and understand mechanistic information. [76] On the basis of the chemical shift, the changes in valence states and coordination environment of the specific element can be precisely analyzed by in situ XPS. However, this surfacesensitive technique with limited detection depth cannot easily reveal the internal changes of bulk electrocatalysts.…”

In Situ Characterization of Catalysis and Electrocatalysis Using APXPS

“…25 As yet, this is the best temporal resolution of APXPS systems reported. This setup was used to study the laser-induced transient surface photovoltage (SPV) effect on Si (100). It demonstrated a monotonic increase of the SPV decay time to laser power.…”

“…Bozzini et al studied carbon deposits on Cu during CO 2 /H 2 O coelectrolysis on a model SOC. 100 Their planar cell design enabled the whole electrochemical system for X-ray beam access and helped confine the active regions of electrocatalysis to the surface for APXPS measurement.…”

“…This reflected an induced surface dipole layer at the interface, which was essentially the effective electric double layer (EDL) at the electrode/gas interface (Figure c). Bozzini et al studied carbon deposits on Cu during CO 2 /H 2 O coelectrolysis on a model SOC . Their planar cell design enabled the whole electrochemical system for X-ray beam access and helped confine the active regions of electrocatalysis to the surface for APXPS measurement.…”

How the surface state of nickel/gadolinium-doped ceria cathodes influences the electrochemical performance in direct CO2 electrolysis

“…To do so, we combine operando near ambient-pressure X-ray photoelectron spectroscopy (NAP-XPS) with online gas phase and electrical measurements over cells with porous NiGDC cathodes. It is important to underline that, contrary to the majority of CO 2 electrolysis NAP-XPS studies which concentrate to the carbon deposition mechanism [5,20,23,24,[29][30][31][32], here we employed operational conditions bellow the carbon deposition threshold, in order to focus on the surface oxidation state and lift complications related to modifications due to irreversible carbon deposition.…”