Group of Gengtao Fu from Nanjing Normal University: Cerium doping regulates CuO configuration matching for efficient electrochemical oxidation of HMF

The electrochemical oxidation of 5-hydroxymethylfurfural (HMFOR) is a promising route for the valorization of biomass towards the sustainable production of high-value 2,5-furandicarboxylic acid (FDCA). However, a fundamental challenge stems from the complex molecular structure of HMF and its derivatives, which contain multiple functional groups such as aldehyde, hydroxyl, and furan ring. Conventional catalysts like copper oxide (CuO) often force these molecules into suboptimal adsorption configurations due to geometric mismatch, resulting in high energy barriers and limited selectivity. The core issue lies in the rigid atomic arrangement of typical catalysts failing to accommodate the spatial requirements of key intermediates during the multi-step oxidation process.

Recently, the team led by Prof. Gengtao Fu at Nanjing Normal University proposed a synergistic strategy involving Ce doping to modulate both the geometric structure and electronic properties of CuO. This approach optimizes the adsorption configuration of intermediates on the catalyst surface, thereby significantly reducing steric hindrance and enhancing HMFOR performance. Experimental results show that the prepared Ce-CuO catalyst achieves an impressive FDCA Faradaic efficiency of 98.4% and a production rate of 67.0 µmol cm^-2 h^-1 at 1.45 V vs. RHE, significantly outperforming undoped CuO. Furthermore, it maintains high Faradaic efficiency over multiple cycles. A combination of in-situ/ex-situ spectroscopic techniques and theoretical calculations reveals that the introduction of Ce not only promotes electron transfer from Ce to Cu, creating electron-rich Cu sites, but also, due to the atomic radius difference, triggers a reconstruction of the coordination geometry. This dual modulation optimizes the geometric matching between active sites and reaction intermediates. Consequently, key intermediates can adopt thermodynamically favorable adsorption configurations with markedly reduced steric hindrance. For instance, the crucial intermediate HMFCA tends to adsorb on the Ce-CuO surface in a configuration much closer to its free state: the spatial compression decreases from 0.48 Å to 0.08 Å, and the molecular bending angle is significantly reduced. This leads to a substantial decrease in the energy barrier of the rate-determining step from 0.99 eV to 0.46 eV.

This study not only demonstrates an effective strategy for geometric configuration engineering via rare-earth element doping but also highlights the critical role of geometric matching in reducing steric hindrance and enhancing reaction pathway selectivity for complex electrocatalytic reactions. It provides a new paradigm for designing efficient biomass electrocatalytic conversion systems and catalysts for other multi-step electrochemical reactions.