Revealing the Behavior of Interfacial Water in Te-Doped Bi via Operando Infrared Spectroscopy for Improving Electrochemical CO2 Reduction

For electrochemical CO2 reduction (CO2RR), proton transfer plays a major role in determining the selectivity, and the behavior of interfacial water is a key factor in the entire process. Herein, tellurium (Te)-doped bismuth (Bi) nanoparticles are prepared on ultrathin nitrogen-doped carbon nanosheets (NCNSs) via an in situ reduction method. Te doping alters the electronic structure of Bi by lowering the oxidation state and increasing oxygen vacancies. The adsorption of H2O molecules at the catalytic interface weakens, as revealed by operando attenuated total reflection surface-enhanced infrared absorption spectroscopy. The weakened water adsorption favors the formation of intermediates and, meanwhile, helps to suppress HER. With the Te dopant, a faradic efficiency above 90% for formate over a broad window from −0.8 to −1.2 V (vs RHE) is achieved, and the partial current density for formate reaches 130 mA cm–2 at −1.2 V (vs RHE) for CO2RR.