Collaborative Electrochemical Oxidation of the Alcohol and Aldehyde Groups of 5-Hydroxymethylfurfural by NiOOH and Cu(OH)2 for Superior 2,5-Furandicarboxylic Acid Production

Abstract

Electrochemical alcohol oxidation is considered a promisingalternative to the oxygen evolution reaction due to the production of high-valueproducts and early onset potential. Herein, we analyze the different reactivitiesof NiOOH and Cu(OH)2toward the electrochemical oxidation of alcohol andaldehyde on the furan ring and utilize their characteristics synergistically toenhance the performance of 5-hydroxymethylfurfural (HMF) to 2,5-furandicarboxylic acid (FDCA) conversion. We discovered that Cu(OH)2hashigher reactivity for the oxidation of aldehyde to carboxylic acid than NiOOH,while NiOOH exhibited excellent reactivity toward the oxidation of alcohol toaldehyde. Furthermore, NiOOH-Cu(OH)2mixed electrodes showed higheractivity and faster conversion of HMF to FDCA than individual NiOOH orCu(OH)2electrodes. The alcohol oxidation of HMF is initiated by NiOOH,and Cu(OH)2quickly converts the remaining aldehydes to carboxylic acids atthe NiOOH/Cu(OH)2interface. Further enhancement of the HMF oxidationkinetics of NiOOH/Cu(OH)2was achieved by preparing a nanofoam structure comprising nanoscale pores and nanodendriticframes, showing instantaneous conversion to FDCA without producing unreacted intermediates.