Attenuated total reflection infrared spectroscopy for studying electrochemical cycling of hydrogen, carbon, and nitrogen-containing molecules

In situ ATR-IR has obtained significant insights into mechanisms of electrochemical hydrogen, nitrogen, and carbon cycling reactions, which provide guidelines on the rational design of more advanced catalysts/interfaces for achieving carbon neutrality. Electrochemical cycling of hydrogen, carbon, and nitrogen-containing molecules is of great importance to tackling energy and environmental crises and composes a central piece of the net-zero emissions scenario. Obtaining an in-depth understanding of interfacial processes with molecular-level information is a cornerstone to developing more advanced electrocatalysts and electrochemical interfaces and further improving reaction efficiencies to meet industrial requirements. Among various in situ characterization techniques that can probe the interfacial processes, attenuated total reflection infrared spectroscopy (ATR-IR) has gained considerable attention most recently. A systematic review of its applications is expected to stimulate further efforts in studying the above-mentioned electrochemical reactions. Herein, we summarize the basic principles of in situ ATR-IR and its applications in understanding mechanisms of electrochemical hydrogen, carbon, and nitrogen cycling reactions, including identification of key reaction intermediates and pathways, deciphering the impacts of interfacial environments, and revealing the structure-to-performance relationship on electrocatalysts. Outlooks on challenges and opportunities faced by ATR-IR in further studying these reactions are also provided.