Accelerated electrochemical-chemical turnover on N-modified Co3O4 with crystalline-amorphous interfaces for efficient glycerol electrooxidation.

Abstract

Electrochemical glycerol oxidation offers a sustainable pathway for valorizing biodiesel-derived glycerol while lowering the energy demand of hydrogen production. However, Co-based catalysts are often limited by inefficient coupling between the electrochemical generation and chemical consumption of oxidized Co species. Herein, a urea-mediated strategy is developed to simultaneously tailor the morphology, surface electronic structure, and local structural order of Co3O4 electrodes. Urea directs the formation of vertically aligned nanoflakes, introduces Co-N coordination, increases the surface Co3+/Co2+ ratio, and generates defect-rich crystalline-amorphous interfacial regions. The optimized Co3O4/NF-5 electrode delivers 1000 mA cm-2 at 1.39 ± 0.02 V, maintains a formate Faradaic efficiency above 84.1 ± 1.4% over 1.3-1.8 V, and exhibits only 3.1% activity decay after 5000 cycles. Electrochemical kinetic analysis, in situ Raman spectroscopy, and potential-step measurements reveal efficient electrochemical-chemical turnover mediated predominantly by CoOOH species, with transient Co4+-associated species potentially contributing at elevated potentials. Density functional theory calculations further indicate that N incorporation modulates Co 3d states and strengthens reactant adsorption. An integrated electrolyzer operates continuously for 216 h, demonstrating device-level durability and favorable preliminary techno-economic prospects. These findings establish coupled morphological and electronic regulation as an effective strategy for promoting electrochemical-chemical turnover in glycerol electrooxidation.