Efficient electrooxidation of 5-hydroxymethylfurfural via phosphate intercalated hydroxides: A dual-cycle mechanism

The electrooxidation of 5-hydroxymethylfurfural (HMF) has emerged as a promising way to generate high-value-added products. However, evoking high-valence state NiOOH species as active sites to realize high current density remains a challenge. Herein, we report an efficient electrocatalyst for HMF electrooxidation based on phosphate anion intercalated layered double hydroxides (NiCo-Pi-LDHs). Onset potential at 1.16 V vs. RHE and current density of 200 mA/cm2 at 1.41 V vs. RHE were realized. The intercalated phosphates act as proton transfer intermediates, facilitating the dehydrogenation of hydroxides to form oxyhydroxides while the protonated phosphate generated. The obtained oxyhydroxide oxidized HMF to 2,5-furandicarboxylic (FDCA) while cycling backward to hydroxide, accompanied by the cycle of protonated phosphate to phosphate. This novel strategy with dual-cycle of phosphate and nickel species can effectively evoke NiOOH species, thereby speeding up the reaction rate and having a great potential for biomass upgrading.