Design and commissioning of a high-temperature electrochemical cell for hard X-ray <i>in operando</i> studies

Solid oxide cells (SOCs) are a promising technology that can both utilize fuel efficiently in fuel cell mode (SOFC) and store energy as fuel in electrolysis mode (SOEC). Of particular interest is the ability to use clean and renewable energy to both electrolyze water to make hydrogen fuel, and convert CO 2 produced during combustion into valuable products such as syngas (H 2 + CO). As a potential cornerstone of a closed-loop sustainable energy system, we must advance our understanding of the electrocatalysts incorporated in SOCs to accelerate the energy transition. Operando X-ray absorption spectroscopy (XAS) is a proven tool for the element-specific characterization of low-temperature electrochemical cells, since it provides local structural and chemical information about the catalyst. However, operando techniques are challenging to apply to SOC studies because their operating conditions, including high-temperature operation, are very demanding. Here, we present an experimental apparatus designed to perform XAS on working electrochemical cells under realistic operating conditions. This cell design is adaptable to any beamline and can be configured to probe both fuel and air electrodes in either the fuel cell or electrolysis cell mode. We present data from commissioning at the SXRMB beamline, demonstrating the ability to obtain XAS and electrochemical measurements from cells at high temperatures. This apparatus has the potential to reveal new insights about SOC reaction mechanisms, leading to more directed design of efficient catalysts.