Nitrogen-doped biochar-supported metal catalysts: High efficiency in both catalytic transfer hydrogenation of furfural and electrocatalytic oxygen reactions

Abstract

The versatility of several N-doped biochar-supported metal catalysts (M/N-BioC) derived from vineyard pruning waste, to promote circular bioeconomy, was evaluated in catalytic transfer hydrogenation (CTH) of furfural (FF), electrocatalytic oxygen reduction and evolution reactions (ORR and OER). The CTH of FF to prepare high valuable chemicals was performed in the presence of formic acid as hydrogen donor at 160 °C, reaching high conversion (up to 80 %) and selectivities towards furfuryl alcohol (ca. 88 %), establishing a promising catalytic route to valorise a biomass platform molecule using 3d-transition metal-based catalysts in absence of molecular hydrogen. The prepared materials also demonstrated moderate ORR electrocatalytic performance in alkaline medium with diffusion-limiting current densities between − 3.48 (Co/N-BioC) and − 1.27 mA cm−2 (Cu/N-BioC) and potential onset values of 0.88 ≥ Eonset ≥ 0.66 V vs. RHE. Additionally, the materials tested showed selectivity towards indirect pathway in which O2 is reduced to H2O2 and then further reduced to water with the number of electrons transferred per O2 molecule ranging from 2.1 to 3.6 electrons. The materials also presented moderate OER electrocatalytic performances in alkaline medium, with overpotential values between 0.48 (Co/N-BioC) and 0.63 V vs. RHE (Fe/N-BioC) and maximum current densities between 0.28 (BioC) and 42.60 mA cm−2 (Co/N-BioC). This research contributes to the development of a new type of promising (electro)catalyst based on biomass residue for biomass valorisation and energy conversion as a promising contribute to the future of biorefineries implementation.