Ce Promotion of In<sub>2</sub>O<sub>3</sub> for Electrochemical Reduction of CO<sub>2</sub> to Formate
Tim Wissink, Floriane A. Rollier, Valery Muravev, Jason M. J. J. Heinrichs, Rim C. J. van de Poll, Jiadong Zhu, Dimitra Anastasiadou, Nikolay Kosinov, Marta C. Figueiredo, Emiel J. M. Hensen
Abstract
High Resolution Image Download MS PowerPoint Slide In 2 O 3 is a promising electrocatalyst for CO 2 electroreduction (CO 2 ER) to formate. In 2 O 3 nanoparticles doped with Pd, Ni, Co, Zr, and Ce promoters using flame-spray pyrolysis were characterized and evaluated in a gas diffusion electrode for the CO 2 ER. Doping results in slight shifts of the In binding energy as probed by XPS, which correlates with a change of the Faradaic efficiency to formate (FE formate ) in the order Ce-doped In 2 O 3 > Zr-doped In 2 O 3 > In 2 O 3 > Pd-doped In 2 O 3 > Ni-doped In 2 O 3 > Co-doped In 2 O 3 . However, the differences in CO 2 ER performance are caused mainly by the different extent of In 2 O 3 reduction. Co-doped In 2 O 3 is prone to complete reduction to a stable Co–In alloy with a low FE formate due to a high hydrogen evolution activity. The stabilizing effect of Ce on In 2 O 3 is further demonstrated by an X-ray absorption spectroscopy study of a set of Ce-doped In 2 O 3 samples (10, 50, 90 at%), highlighting that reduction of In 2 O 3 is suppressed with increasing Ce content. Optimum performance in terms of FE formate is obtained at a Ce content of 10 at%, which is attributed to the stabilization of In 2 O 3 under negative bias up to −2 V. At higher Ce content, less active CeO 2 is formed. The highest FE formate of 86% observed for In 2 O 3 doped with 10 at% Ce, at a current density of 150 mA/cm 2, compares favorably with a FE formate of 78% for In 2 O 3 .