Bimetallene catalyst enables energy-efficient biomass conversion

The sustainable production of fuels and value-added chemicals from biomass is a cornerstone of the future bioeconomy. 5-hydroxymethylfurfural (HMF), a platform molecule derived from lignocellulosic biomass, holds immense promise for replacing petroleum-derived building blocks. Its selective hydrogenation to 2,5-dihydroxymethylfuran (DHMF), a crucial precursor for pharmaceuticals, nucleoside analogs, and specialty polymers, is of particular interest. However, conventional thermocatalytic HMF hydrogenation often necessitates harsh conditions (high temperatures and pressures), leading to substantial energy consumption and process intensification challenges.

A recent breakthrough, published in the Chinese Journal of Catalysis, presents a compelling alternative: electrochemical hydrogenation (ECH) at ambient conditions. A research team led by Prof. Yu Chen from Shaanxi Normal University, China, has developed a highly alloyed Pd₃Pt₁ bimetallene (Pd₃Pt₁BML) that enables the energy-saving ECH of HMF to DHMF.

This novel Pd₃Pt₁ BML synthesized via a facile galvanic displacement reaction, exhibits a unique two-dimensional metallene structure. This morphology, combined with the atomically-dispersed Pt within the Pd lattice, provides distinct catalytic advantages. The catalyst demonstrates a remarkable Faradaic efficiency exceeding 93% and a DHMF selectivity surpassing 66% under mild conditions.

The exceptional performance of the Pd₃Pt₁ BML stems from a synergistic interplay of geometric and electronic effects. In-situ Raman spectroscopy provides compelling evidence of the weakened HMF adsorption on Pd sites. Density functional theory (DFT) calculations corroborate this observation, highlighting the critical role of Pt in promoting hydrogen spillover and facilitating the hydrogenation process. The atomically dispersed Pt not only mitigates catalyst poisoning by reducing the binding strength of HMF on Pd, but also serves as a source of abundant active hydrogen species, thereby accelerating the overall conversion.

A key innovation of this work is the strategic coupling of HMF ECH (at the cathode) with the formic acid oxidation reaction (FAOR) at the anode. This paired electrolysis approach circumvents the kinetically sluggish oxygen evolution reaction (OER), which typically limits the efficiency of electrochemical systems. The assembled Pd₃Pt₁ BML||Pd₃Pt₁ BML electrolyzer system reaches a current density of 10 mA cm^-2 at a remarkably low cell voltage of only 0.72 V for HMF ECH.

This presents a substantial voltage reduction of nearly 1 V compared to analogous HMF ECH systems coupled with OER, translating to a significant decrease in energy consumption. The synergistic ensemble and electronic effects of Pd-Pt structure are central to achieving both high catalytic activity and excellent selectivity toward DHMF production.