Evaluation of ternary iron nickel boride electrocatalysts in sustainable electrochemical energy production

Here, the potential of earth-abundant boride-based catalysts for integrated hydrogen production and biomass valorisation was explored. Durable transition metal borides were synthesised via a low temperature wet-chemical approach and incorporation of a second metal allowed amorphous monometal nickel boride to be compared with bimetallic borides (of varying Fe:Ni ratio). The composites were systematically characterised using surface (scanning electron microscopy, transmission electron microscopy, X-ray diffraction and X-ray photoelectron spectroscopy) and electrochemical techniques (voltammetry, electrochemical impedance spectroscopy, Tafel analysis) to establish their relative morphological and electrocatalytic characteristics. The optimum composition yielded Akaganeite-nickel boride (β-FeOOH-NiB) which was confined on a carbon cloth porous support. This resulted in very good performance for the alkaline hydrogen evolution reaction with low onset potential (10 mV) and overpotential of 80.3 mV vs RHE at j = 10 mA cm −2 being very competitive with respect to the Pt benchmark. 60 h stability testing resulted in potential values of −64.8 mV and −265.4 mV vs . RHE at 10 and 100 mA cm −2 , respectively, indicative of the good durability of the catalyst over this extended timescale. The ternary β-FeOOH-NiB electrocatalytic material was also confined on a pressed nickel foam substrate and examined for both the oxygen evolution reaction (OER) and glucose and glycerol electrooxidation reactions. Replacing the OER with a more thermodynamically favourable process can reduce the overall energy demand and the system required 1.51 V vs RHE to deliver 10 mA cm −2 in the presence of 0.1 M glucose and 1.52 V in the presence of 0.1 M glycerol. The data presented confirms that the β-FeOOH-NiB composite is an attractive and scalable candidate for sustainable hydrogen production, coupled with biomass derived feedstocks.