Low-Content Co-Modified Carbon Nitride With Co-N Bond as an Efficient and Stable Catalyst for Electrocatalytic Oxidation of 5-Hydroxymethylfurfural

The traditional noble metal and transition metal catalysts encounter challenges due to the high cost and potential environmental pollution in the electrocatalytic 5-hydroxymethylfurfural oxidation reaction (HMFOR). The construction of the Co-N bond not only can reduce the excessive use of metals but also effectively enhances the electrocatalytic performance by increasing the electron transfer rate and promoting the adsorption of key intermediates. In this work, low-content Co-modified carbon nitride (CN) with a Co-N bond (1% Co-CN/NF) was constructed as an electrocatalytic catalyst for HMFOR, and excellent FDCA production yield could be achieved in both low-concentration (10 mM) and high-concentration HMF (100 mM). In situ/ex situ characterization combined with DFT calculation confirmed that the formation of the Co-N bond enhanced the electron transport rate during the HMFOR process, reduced the adsorption potential of HMF on the electrode, and promoted the adsorption of HMF; thus, the HMFOR performance was effectively improved. Subsequently, based on its potential application prospects, the experimental conditions were optimized by the XGBoost model of machine learning (ML) to achieve obvious performance improvement (achieving 100% of HMF conversion, 99.04% of FDCA yield, 98.86% of FE, and 24 cycles of stability) in 10 mM HMF, and the results were higher than those of currently reported organic electrocatalysts and even most Co-based electrocatalysts. It was exciting that superior FDCA productivity yield and recovery yield were obtained in a photovoltaic electrocatalysis (PVEC) system with 100 mM HMF. This work is expected to provide precise and detailed insights into the further construction of a novel low-budget, environmentally friendly, efficient, and stable HMFOR system.