Electrochemical upgrading of biomass-derived 5-hydroxymethylfurfural and furfural over oxygen vacancy-rich NiCoMn-layered double hydroxides nanosheets

Rational design of low-cost and active electrocatalysts is crucial for upgrading of biomass-derived chemicals. Here, we report highly efficient catalysts ternary NiCoMn-layered double hydroxides (NiCoMn-LDHs) nanosheets which are oxygen vacancy-rich, produced under controllable conditions for the electrooxidation of both 5-hydroxymethylfurfural (HMF) to 2,5-furandicarboxylic acid (FDCA) and furfural to furoic acid (FurAc) under mild conditions, respectively. Electrochemical tests showed that the oxidation of HMF and furfural occurred prior to the oxidation of water at lower applied potentials with NiCoMn-LDHs catalysts. High yields of FDCA (91.7%) and FurAc (92.4%) were achieved in 2.5 h using 1.15 nm thick NiCoMn-LDHs nanosheets under the optimal conditions. The mechanism for the superior performance, high durability, and good faradaic efficiency has been elucidated by comprehensive characterization, which confirmed that ultrathin nanosheets expose more Co-NiOOH active sites with oxygen vacancies, facilitating the synergistic effect between HMF and furfural oxidation reaction on Co-Ni and Mn2+ states. The oxygen vacancy-rich NiCoMn-LDHs nanosheet catalysts present a novel and energy-efficient solution to obtain upgraded biochemicals.

Automated summary

A highly efficient ternary NiCoMn-layered double hydroxides (NiCoMn-LDHs) nanosheet catalyst with oxygen vacancy-rich properties has been developed for the electrooxidation of HMF and furfural to FDCA and FurAc, showing high yields and good faradaic efficiency. The mechanism for its superior performance lies in the exposure of more active sites with oxygen vacancies, promoting synergistic effects between HMF and furfural oxidation reactions.