Optimized NiFeP alloy for overall water-splitting

Abstract

To achieve efficient electrochemical processes for the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER), it is essential to develop rational designs and innovative modifications to low-cost, high-performance electrocatalysts able to work in direct connection with renewable sources. This paper presents the behavior of nanostructured NiFeP electrocatalysts to use for both HER and OER. The electrodes consist of nanowire arrays with a large surface area, ensuring high electrocatalytic activity. The most promising results were obtained for the OER, with a Tafel slope of 40 mV/dec. Electrodes demonstrate good stability over time without any evident signs of performance decay. Also, in the case of operation under intermittent power supply, applying current profiles typical of a day-night cycle of photovoltaic and wind energy, good performance was obtained. A lab-scale electrolyzer was fabricated and tested for a continuous operation of 6 h at 50 and 100 mA/cm2, reaching a potential of 1.91 and 2.01 V, respectively, for overall water-spitting. Furthermore, the environmental impact of the manufacturing process of NiFeP nanowires was evaluated by applying the Life Cycle Assessment methodology, which is employed to assess the energy and environmental impacts of the life cycle of electrodes produced by the electrodeposition method.