Comparison of Modifications for Enhancing the Electrooxidation Performance of Porous Ni Foil Catalytic Electrodes Derived from Paper Templates: Cu-Added Alloying and In Situ Growth of Ni-S Nanosheets

Improving the performance of porous nickel-based material used widely in the energy field is necessary. Alloying and increasing the specific surface area are essential approaches. This study used rice paper (Chinese traditional calligraphy and painting paper) as biomass templates to prepare hierarchical porous Ni and Ni-Cu foils (Ni_p and NiCu_p) with a thickness of about 60 μm by impregnating and high-temperature reduction process. The Ni₃S₂/Ni_p electrodes were prepared by an in situ-grown Ni₃S₂ nanosheet array on the struts of Ni_p via a hydrothermal process. Two modification methods using Cu-added alloying and Ni-S nanosheet growing were compared to determine their effects on the microstructure, phase, and performance in methanol oxidation (MOR) and urea oxidation (UOR). The results showed that both alloying effects and morphology control can promote MOR and UOR. Compared to the current density value of Ni_p at 0.8 V, the values of the preferred Ni₁₀Cu_p and nanosheet array Ni₃S₂/Ni_p increased by 24.5% and 27.3% for methanol oxidation and by 15.4% and 38.4% for urea oxidation, respectively. Adding Cu helped to improve electron transfer and facilitated the transition from Ni²⁺ to Ni³⁺. The large specific surface area of Ni₃S₂ nanosheets provided more active sites for the reaction. Compared to Ni₁₀Cu_p, Ni₃S₂/Ni_p with a lower impedance value exhibits better electrocatalytic performance and stability, achieving peak current densities of 269.7 mA cm⁻² (MOR) and 303.9 mA cm⁻² (UOR) at 0.8 V, maintaining 91.2% (MOR) and 102.4% (UOR) of the initial peak current density after 2000 cycles. The foil electrodes obtained under both modification strategies can be used as anode material in portable cells, and might also be applied to the oxidation of other small organic molecules.

Graphical Abstract