Ni-Co bimetallic sulfide-derived catalysts for efficient electrooxidation of xylose to formate

Co doping tailors Ni redox chemistry and creates ultrathin nanosheet arrays. • PA-NiCoS@NF delivers 80.1% formate yield and 80.9% FE at 1.45 V vs. RHE. • Xylose oxidation requires 251 mV less potential than OER at 50 mA cm −2 . • In situ Raman identifies dynamically formed NiCoOOH as the reactive phase. Abundant xylose from agroforestry residues can be electrocatalytically oxidized to formate, offering a promising green biomass valorization strategy for carbon neutrality. Herein, a novel post-activated (PA) Ni-Co bimetallic sulfide-derived electrocatalyst supported on a nickel foam substrate for the xylose oxidation reaction (XOR), denoted as PA-NiCoS@NF, was fabricated via a facile one-step electrodeposition method. Co doping induces the formation of an ultrathin nanosheet array structure. Furthermore, it enables precise modulation of the electronic structure of the Ni centers, and the strong electronic interaction between Co and Ni bimetallic sites facilitates the oxidation of Ni 2+ to Ni 3+ . The PA-NiCoS@NF catalyst exhibits outstanding electrocatalytic performance for XOR, delivering a xylose conversion of 99.9%, a formate yield as high as 80.1% with a formate selectivity of 81.0%, a corresponding Faradaic efficiency of 80.9% at a low potential of 1.45 V vs. RHE. Additionally, the XOR delivers a current density of 50 mA·cm⁻² at only 1.39 V vs. RHE. Density functional theory calculations reveal that Co doping optimizes the adsorption behaviors of xylose and adsorbed hydroxyl species on the active sites. Furthermore, the PA-NiCoS@NF catalyst exhibits excellent cycling stability for XOR and increased anodic current responses in a preliminary LSV screening of five biomass-derived substrates. This work provides a novel and feasible strategy for the electronic structure modulation and nanostructure engineering of high-efficiency catalysts in the field of electroconversion of aldose biomass platform molecules. Download: Download high-res image (210KB) Download: Download full-size image