The electrocatalytic activity and selectivity of ethylene glycol oxidation into value-added chemicals at iron-group electrodes in alkaline media

Selective electrocatalytic conversion via ethylene glycol oxidation reaction (EGOR) at abundant Iron-group catalysts could be a promising and sustainable approach to produce value-added C1 and C2 chemicals. However, the corresponding intrinsic electrocatalytic activity and selectivity of EGOR on Iron-group electrodes are still ambiguous, which is urgent to be revealed. The linear scanning voltammetry (LSV) results show that Co and Ni rather than Fe exhibit considerably high activity, and the CoIV and NiIII sites formed at high potential might be crucial for the fast EGOR revealed by LSV and operando electrochemical impedance spectroscopy (EIS). Then, the in-situ electrochemical infrared absorption spectroscopy (IRAS) and high-performance liquid chromatography (HPLC) are used to obtain a general understanding of reaction pathways and product distributions in alkaline media. Specifically, a parallel C1 pathway (formate) without CO2 generation and C2 pathway (glycollate, oxalate) is confirmed on Co and Ni surfaces. The C1 pathway is dominated on the Ni surface with a ∼60% selectivity of formate, while the C2 pathway is favorable on the Co surface with a ∼43% selectivity of glycollate at 1.60 V vs. RHE. In addition, the Ni electrode showed a higher yield rate of carboxylate products. This work may offer theoretical guidance for the design of noble-metal-free electrocatalysts towards efficient selective electrooxidation of EG to value-added chemicals.