Biomass is among the most abundant renewable resources on earth. Through catalytic conversion, biomass can upgrade into a series of fuels and chemicals which can substitute traditional fossil resources, thus playing a crucial role in achieving the "carbon peaking and carbon neutrality" target.

A group of Chinese scientists have recently developed a novel MAX phase with single-atom-thick cobalt layers, achieving high-efficiency electrocatalysis of 5-hydroxymethylfurfural (HMF) oxidation coupled with hydrogen evolution.

MAX phases are a family of layered ternary metal carbides or nitrides that have attracted great attention as structural materials due to their outstanding structural diversities, mechanical properties, and application potential.

Prof. ZHANG Jian's team at the Ningbo Institute of Materials Technology and Engineering (NIMTE) of the Chinese Academy of Sciences (CAS), in cooperation with Prof. HUANG Qing's team at NIMTE and Prof. LI Youbing at Soochow University, introduced cobalt, a highly catalytic and cost-effective transition metal, into the A-site of MAX phases.

The obtained V₂(Sn_2/3Co_1/3)C MAX phase was applied as a high-efficiency electrocatalyst for the HMF oxidation along with hydrogen evolution in an alkaline electrolyte. This achieved complete biomass HMF conversion and a 94.4% 2,5-furandicarboxylic acid (FDCA) yield at 1.60 V throughout six hours in the two-electrode system.

Besides, the FDCA production rate reached 8.02±0.64 mmol_FDCA⋅g_cat.^-1⋅h^-1 in the 100 mM HMF electrolyte, surpassing many traditional electrocatalysts and thermocatalysts.

Density functional theory (DFT) calculations indicated that the Co-Sn synergy in the A-site facilitated the adsorption and electrocatalytic conversion of HMF, therefore transforming MAX phases from structural materials into functional materials.

Moreover, HMF can significantly inhibit the surface reconstruction of MAX phases and competitive oxygen evolution reaction. Therefore, the structure of MAX phases remained intact even after the electrolysis in harsh 1 M KOH alkaline electrolyte.

The excellent electrocatalytic performance and structural stability of biomass upgrading demonstrated the broad potential of MAX phases for applications in energy storage, green catalysis, and other challenging chemical environments.

Results of the study were published in Chemical Engineering Journal.

This work was supported by the National Natural Science Foundation of China, the Leading Innovative and Entrepreneur Team Introduction Program of Zhejiang, Zhejiang Province Natural Science Foundation of China, Key Research and Development Program of Zhejiang Province, Ningbo Science and Technology Bureau, and Ningbo Natural Science Foundation.

MAX phases boost electrocatalytic biomass HMF upgrading with an impressive FDCA yield (Image by NIMTE)