Synergistic Nickel-Molybdenum Carbide-Graphite Nanofiber Composite Catalyst for Enhanced Green Hydrogen Production Through Ethanol Electrooxidation

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Abstract Novel nickel-molybdenum carbide-graphite nanofiber composite is introduced as an electrocatalyst to produce green hydrogen from ethanol electrooxidation. The proposed nanofibers have been prepared by calcinating electrospun nanofibers composed of nickel acetate tetrahydrate, molybdenum chloride, and poly (vinyl alcohol). Physicochemical characterizations have indicated that during the sintering process, nickel acetate is entirely reduced to nickel metal, and molybdenum has bonded with carbon to produce molybdenum carbide. At the same time, the used polymer has been pyrolyzed to produce a carbon nanofiber matrix embedding formed inorganic nanoparticles. Electrochemical measurements concluded that both molybdenum content and calcination temperature should be controlled to maximize the electrocatalytic activity of the proposed catalyst. Typically, the oxidation peak current density was 28.5, 28.8, 51.5, 128.3, 25.6, and 3 mA/cm2 for nanofibers prepared from an electrospun solution containing 0, 5, 10, 15, 25, and 35 wt% molybdenum carbide, respectively. Moreover, the optimum calcination temperature was found to be 1000 oC. Kinetic studies have indicated that the order of reaction is close to zero with a reaction temperature-dependent value. Moreover, it was detected that electrooxidation reaction of ethanol over the proposed nanofiber composite follows Arrhenius equation, the determined activation energy is 33 kJ/mol which indicates good catalytic activity of the introduced nanofibers. Through the application of a set of visualization-based tools and the general linear model (GLM), the optimal conditions that generate the highest current density were identified. The computations unveiled that the optimal parameter settings are as follows: Mo content at 15 wt.%, methanol concentration of 1.55 M, and reaction temperature of 59°C.

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