Mechanistic Insights into the Role of Elements in Ni-Co-P Catalysts for Electrochemical Conversion of 5-Hydroxymethylfurfural to 2,5-Furandicarboxylic Acid

Abstract

Ni phosphides and NiCo alloys are extensively explored for their remarkable efficiency in biomass alcohol oxidations, yet the underlying mechanisms remain inadequately understood. This study thoroughly elucidates the roles of Ni, Co, and P in improving the catalytic performance of Ni-Co-P catalysts for the electrochemical conversion of 5-hydroxymethylfurfural (HMF) to 2,5-furandicarboxylic acid (FDCA), a promising biomass-derived building block replacing terephthalic acid. Phosphorization of Ni results in the partial formation of Ni2P phase and significantly boosts the formation of the reactive NiOOH phase on the surface, which is the crucial catalytic phase for converting HMF into FDCA. The integration of Co into the heterojunction between Ni2P and NiOOH enhances the oxidation reactivity of 5-formyl-2-furancarboxylic acid (FFCA), a pivotal intermediate influencing FDCA productivity, by selectively stabilizing aldehydes, thereby promoting further oxidation rather than surface desorption. in situ/operando spectroscopic analyses consistently highlight the equal significance of the rapid generation of NiOOH and the robust adsorption of reactant molecules at the surface in achieving high catalytic performance. These insights into elemental contributions set a new standard for designing multi-component electrocatalysts for efficient biomass alcohol oxidation. Phosphorization of Ni and Co doping creates a NiOOH/Co-doped Ni2P heterojunction, facilitating HMF chemisorption and stabilizing aldehyde bonds, significantly enhancing FDCA productivity. Computational modeling outlines the entire HMF-to-FDCA conversion pathway, detailing the energetic changes driven by the heterojunction. In situ/operando Raman and IR analyses provide critical observations of changes in the catalyst surface and reactants during the reaction. image