A sustainable approach using natural phosphates impregnated with nickel hydroxide nanoparticles: a cost-effective solution for alcohol oxidation'

Abstract

This study introduces a novel and effective approach for the electrocatalytic oxidation of alcohols, showcasing the development of a highly active and cost-effective anode catalyst for methanol and ethanol. A dual-embedded Ni electrode, named (Ni@NATPhos/Ni), is based on a carbon paste electrode modified with natural phosphate impregnated with nickel ions. A layer of nickel nanoparticles was then added via electrochemical deposition, using a precise combination of wet impregnation and potentiostatic electrodeposition techniques. Characterization using XRD and TEM revealed the formation of crystalline structures such as nickel pyrophosphate (Ni₂P₂O₇) and orthophosphate (Ni₃(PO₄)₂), along with nickel hydroxides (Ni(OH)₂), resulting in well-distributed homogenous nickel nanosized particles of approximately 30 nm. The electrocatalytic performance of Ni@NATPhos/Ni was assessed and compared with an unmodified carbon paste electrode in alkaline media. With peak current densities of 110 mA cm⁻² for methanol and 83 mA cm⁻² for ethanol oxidation, the synthesized catalyst demonstrated significantly improved catalytic efficiency. After 500 CV cycles, the dual-embedded electrode Ni@NATPhos/Ni demonstrated excellent stability, retaining 70.33% and 61.58% of its initial current values for ethanol and methanol, respectively, and exhibiting high tolerance to intermediate species poisoning. Electrochemical impedance spectroscopy (EIS) conducted after stability testing revealed an increase in solution resistance, indicative of the complete oxidation of intermediate species in the alkaline solution. The synthesized Ni@NATPhos/Ni electrode emerges as a promising and robust catalyst for alcohol oxidation reactions, offering significant advancements in electrocatalytic efficiency and stability.