In situ-generated PdH<i><sub>x</sub></i> promotes electrochemical CO<sub>2</sub> conversion to CO.

Zhang, Yifan; Wang, Xiaoyuan; Zou, Yu-Ling; Xu, Yujing; Yang, Xiaoju; Li, Linfeng; Zhang, Li; Wei, Zhiming et al. · Sci Adv · 2026

basic_science · Level V

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Abstract

Palladium-based catalysts have been recognized to be active for the production of syngas with controlled carbon monoxide (CO)/hydrogen gas ratios via the electrochemical carbon dioxide (CO<sub>2</sub>) reduction reaction (CO<sub>2</sub>RR); however, the active phase remains the subject of debate. In this work, we have found that the Faradaic efficiency of CO is linearly dependent on the hydride stoichiometry of in situ-generated palladium hydride (PdH<i><sub>x</sub></i>) for palladium (Pd)-based catalysts, despite their different composition, size, and morphology, as well as the applied potential. The active phase for the production of CO via the CO<sub>2</sub>RR on the surfaces of Pd-based catalysts is revealed to be in situ-generated PdH<i><sub>x</sub></i>. In situ surface-enhanced infrared absorption spectroscopy and electro-optical imaging results demonstrate that in situ-generated PdH<i><sub>x</sub></i> is totally different from chemically synthesized PdH<i><sub>x</sub></i>. Density functional theory calculations demonstrate that the higher stoichiometry of in situ-generated PdH<i><sub>x</sub></i> promotes CO production. Our results provide insights into the rational design of Pd-based catalysts with improved CO<sub>2</sub>RR performance.