Boosting Formate Production in Electrocatalytic CO₂ Reduction over Wide Potential Window on Pd Surfaces

Abstract

Facile interconversion between CO and formate/formic acid (FA) is of broad interest in energy storage and conversion and neutral carbon emission. Historically, electrochemical CO reduction reaction to formate on Pd surfaces was limited to a narrow potential range positive of -0.25 V (vs RHE). Herein, a boron-doped Pd catalyst (Pd-B/C), with a high CO tolerance to facilitate dehydrogenation of FA/formate to CO, is initially explored for electrochemical CO reduction over the potential range of -0.2 V to -1.0 V (vs RHE), with reference to Pd/C. The experimental results demonstrate that the faradaic efficiency for formate (η) reaches ca. 70% over 2 h of electrolysis in CO-saturated 0.1 M KHCO at -0.5 V (vs RHE) on Pd-B/C, that is ca. 12 times as high as that on homemade or commercial Pd/C, leading to a formate concentration of ca. 234 mM mg Pd, or ca. 18 times as high as that on Pd/C, without optimization of the catalyst layer and the electrolyte. Furthermore, the competitive selectivity ηη on Pd-B/C is always significantly higher than that on Pd/C despite a decreases of η and an increases of the CO faradaic efficiency (η) at potentials negative of -0.5 V. The density functional theory (DFT) calculations on energetic aspects of CO reduction reaction on modeled Pd(111) surfaces with and without H-adsorbate reveal that the B-doping in the Pd subsurface favors the formation of the adsorbed HCOO*, an intermediate for the FA pathway, more than that of *COOH, an intermediate for the CO pathway. The present study confers Pd-B/C a unique dual functional catalyst for the HCOOH ↔ CO interconversion.

Metal Nanoclusters: New Paradigm in Catalysis for Water Splitting, Solar and Chemical Energy Conversion

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Enhancing Electroreduction of CO2 to Formate of Pd Catalysts Loaded on TiO2 Nanotubes Arrays by N, B‐Support Modification

“…It should be poninted out that Pd is still the most promising cathode catalyst that enables to convert CO 2 into formate at very low overpotential . However, we also note that the high selectivity for CO 2 ER to formate is limited to very narrow potential window negative to 0 V (vs RHE) in KHCO 3 , which may restric the synthesis rate of formate product . According to the study of Gao et al., the product of CO 2 ER is greatly influenced by the hydrogen adsorbed state on Pd surface, i. e., the formation of the α+β PdH x @PdH x active phase above −0.2 V (vs RHE) facilitates formate production.…”

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Porous Palladium Nanomeshes with Enhanced Electrochemical CO2‐into‐Syngas Conversion over a Wider Applied Potential

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