Ni3S2-La2O3 Heterojunction Loading by Lignin-Derived Porous Carbon Catalysts for Efficient HMF Oxidation

Ni 3 S 2 -La 2 O 3 heterojunction on sulfur-doped carbon is fabricated. • It achieves 99.05% HMF conversion and 96.62% FDCA selectivity. • Heterojunction boosts charge transfer and lowers reaction energy barrier. • The catalyst reconstructs into Ni(OH) 2 /La 2 O 3 as the true active phase. Herein, we report a ball milling pyrolysis route to prepare highly dispersed Ni 3 S 2 /La 2 O 3 heterostructure nanoparticles immobilized on sulfur-doped carbon (Ni 3 S 2 /La 2 O 3 @SC) for the electrocatalytic oxidation of 5-hydroxymethylfurfural (HMF). Structural characterizations combined with theoretical calculations confirm that the formation of the La 2 O 3 /Ni 3 S 2 heterojunction interface modulates the electronic structure of Ni active sites, thereby enhancing HMFOR performance. Electrochemical performance evaluation shows that Ni 3 S 2 /La 2 O 3 @SC achieves a current density of 100 mA·cm -2 at a potential of 1.697 V vs. RHE, while exhibiting enhanced kinetics for HMF oxidation. I n- situ electrochemical impedance spectroscopy (EIS) further reveals that interfacial charge transfer effectively suppresses the competing oxygen evolution reaction (OER) and promotes HMF oxidation. Through reaction monitoring by high-performance liquid chromatography (HPLC), it is demonstrated that HMF is predominantly converted to 2,5-furandicarboxylic acid (FDCA) via the HMFCA pathway. Under a constant current density of 100 mA·cm -2 , Ni 3 S 2 /La 2 O 3 @SC achieves a HMF conversion of 99.05%, an FDCA selectivity of 96.62%, and a Faradaic efficiency of 82.60%. Density functional theory (DFT) calculations further reveal that the formation of the La 2 O 3 /Ni(OH) 2 heterojunction interface not only suppresses the over-adsorption of HMF on Ni–OH sites and lowers the reaction energy barrier for the critical FDCA desorption step in HMFOR, but also enhances charge transfer between reactants and active sites, thereby facilitating the cleavage of key α-C–H and –O–H bonds during HMFOR. The above studies demonstrate the critical role of interfacial charge transfer in modulating the oxidative activity of Ni–OH active sites and enabling efficient HMFOR. Download: Download high-res image (373KB) Download: Download full-size image