Co 3 O 4 -Supported NiFe-Based Sulfide/Hydroxide Heterojunction for Efficient Oxygen Evolution Reaction and Methanol Sensing

This study successfully constructed a three-dimensional composite electrode material on nickel foam (NF) by first synthesizing the precursor via a hydrothermal method, then subjecting it to calcination and final sulfidation treatment. This process yielded a Co(OH) 2 -derived Co 3 O 4 -supported NiFe-based sulfide/hydroxide heterojunction. This composite exhibits excellent oxygen evolution reaction (OER) catalytic performance, requiring an overpotential of only 205 mV to achieve a current density of 10 mA cm –2 in 1 M KOH. The Tafel slope is 29.3 mV dec –1 . After a 60 h constant current test, it maintains 93.2% of its initial current density, with the overpotential increasing by only 4 mV, demonstrating outstanding structural stability. Simultaneously, the material exhibits high sensitivity and selectivity toward methanol oxidation; the sensor demonstrated a limit of detection (LOD) of 0.1581 μM and a limit of quantification (LOQ) of 0.5270 μM for methanol. Such bifunctional characteristics underscore its potential for applications in clean energy conversion and the early screening of lung cancer within occupational cohorts. The remarkable performance enhancement originates from the effective dispersion of active sites and the facilitated electron transport enabled by the three-dimensional conductive Co 3 O 4 precursor framework, coupled with the likely synergistic effect arising from the possible formation of a heterojunction between the generated Ni 3 S 2 and the residual (oxy)hydroxides during the sulfidation process. This synergy optimizes the electronic structure of the material and improves its stability.