Proton transfer mediator for boosting the current density of biomass electrooxidation to the ampere level

Abstract

Lack of catalysts that can simultaneously achieve high current densities and faradaic efficiencies poses substantial barriers to the widespread implementation of biobased alcohol and aldehyde electrooxidation. To tackle kinetic challenges, we proposed a strategy of using a transfer mediator to accelerate the proton coupled electron transfer during dehydrogenation of biobased alcohols and aldehydes on the surface of Ni(OH)₂. Taking 5-hydroxymethylfurfural (HMF) as an example, through DFT calculations, it is found that the embedding of phosphate on Ni(OH)₂ can elongate the O–H bond of the HMF molecule and promote its breaking. By coupling with the modification of the bandgap of Ni(OH)₂ by Ru, the energy barrier of the HMF dehydrogenation process drastically reduces theoretically. Experiments show that the catalytic performance of PO₄/Ru–Ni(OH)₂/NF is much higher than that of Ni(OH)₂/NF, and a current density of more than 1000 mA cm⁻² at a potential of 1.45 V with high selectivity for FDCA (98%) and a faradaic efficiency of 97% are obtained. Characterization and in situ measurements demonstrate the modulation of the bandgap by Ru and the acceleration of the proton-coupled electron transfer process on the surface of PO₄/Ru–Ni(OH)₂/NF, consistent with theoretical calculations. This work proposes an original concept for improving electrochemical performance and supports it experimentally, providing a new idea for scientifically designing industrial scale performance catalysts for biobased alcohol and aldehyde electrooxidation in the future.