A methodical strategy for achieving efficient electro-solar reduction, incorporating appropriate in situ techniques

Solar-to-fuel production via the carbon dioxide (CO₂) reduction reaction (CO2RR) is a crucial and widely discussed topic, particularly in the context of climate change. Electro-solar approaches, such as electrochemical (EC), photochemical (PC), and photoelectrochemical (PEC) methods, are promising for CO2RR due to their efficiency and mild operating conditions. The process of converting CO₂ into valuable products involves multiple steps and requires a deep understanding of reaction mechanisms and product selectivity. In situ and operando spectroscopic techniques are essential for elucidating these mechanisms. This review focuses on advanced in situ spectroscopic methods, such as X-ray absorption spectroscopy (XAS), infrared (IR) spectroscopy, Raman spectroscopy, and electron paramagnetic resonance (EPR) spectroscopy, which provide insights into CO₂ adsorption, activation, and electron-proton transfer, leading to intermediate radical formation. Additionally, advanced X-ray techniques are briefly discussed, offering refined approaches to studying CO2RR dynamics. These integrated techniques are crucial for designing and optimizing catalysts for efficient CO₂ reduction and conversion.