Perfect Carbon Balance in Electrooxidation of 5-Hydroxymethylfurfural to Formic Acid Over Fe-MoS₂

The selective catalytic conversion of biomass-derived 5-hydroxymethylfurfural (HMF) into high-value chemicals represents a critical pathway toward sustainable chemical synthesis and carbon neutrality. However, precise control over the oxidation degree to avoid over-oxidation to CO₂ remains a formidable challenge. Herein, we report a two-dimensional (2D) Fe-MoS₂ catalyst that enables highly selective electrooxidation of HMF to formic acid (FA) with near-complete carbon retention. Leveraging the unique electronic structure of the MoS₂ substrate, the Fe-MoS₂ catalyst achieves a FA yield of 86% and a Faradaic efficiency of 95% at an applied potential of 1.52 V vs. RHE, alongside excellent cycling stability and a nearly 100% carbon balance. Mechanistic investigations reveal that the high work function and suitable valence band position of Fe-MoS₂ create an electron-rich interface that stabilizes carboxylic acid intermediates, while its large specific surface area and mesoporous architecture physically suppress over-oxidation. Density functional theory (DFT) calculations further demonstrate a lower energy barrier for FA stabilization, promoting selective oxidative bond cleavage. This work highlights the critical role of modulating catalytic selectivity for providing 100% carbon balance in biomass valorization.