Gold Ultralow Loading on Nickel Foam for Nitrogen Electrochemical Reduction

Abstract

Gold electroless deposition on nickel foam offers several advantages over traditional electrodeposition techniques. One of the main advantages is that it can produce uniform thickness coatings on complex shapes and geometries, such as porous and three-dimensional substrates like nickel foam. The resulting gold-nickel foam composite has high surface area and good electrical conductivity, making it suitable for various electrochemical applications, including catalysis, sensing, and energy storage.In this work we focused on the development of synthetic strategies to grow and optimize the surface coverage of gold on nickel foam and the evaluation of its suitability for the electrochemical reduction of nitrogen for ammonia synthesis.The gold electroless deposition on Ni Foam has been obtained by immersion in aqueous solution containing KAuCl4 and HCl, with or without stirring and addition of a surfactant agent (Isopropyl Alcohol). Depositions were performed by varying the immersion time from 30 seconds to 30 minutes. Scanning electron microscopy (SEM) has been employed to compare different deposition conditions and to optimize the morphology of the nanofilms, allowing higher catalytic activity. The electrochemical performance of the gold deposited on nickel foam was evaluated in a standard two compartments electrochemical cell using a Pt wire as counter electrode (CE), a saturated calomel electrode (SCE, saturated KCl) as reference and 0.1 M Na2SO4 solution as electrolyte. Electrochemical active surface area (EASA) and linear sweep voltammetry (LSV) have been adopted to evaluate the active area and the overpotential toward hydrogen evolution reaction (HER). Chronoamperometry experiments were carried out at various potentials to evaluate the performance of the catalyst for the electroreduction of nitrogen and ammonia synthesis.The amount of ammonia produced was measured by the indophenol blue method.The maximum NH3 yield of 2.8x10-11 mol s-1 cm-2 was achieved at -0.045 V vs RHE. The maximum faradaic efficiency of 5.8% was achieved at more positive potential (0.015 V vs RHE) due to the HER.The results show that the gold on nickel foam exhibits excellent electrochemical stability and high conductivity.This project has received funding from the European Union’s Horizon 2020 Research and Innovation programme under grant agreement No 101006941. This project started on the 1st of November 2020 with a duration of 42 months.