Design of Zero-Gap Alkaline Electrolyzer with Nanostructured Electrodes for Hydrogen Production

Abstract

A sustainable way to produce clean hydrogen is through water splitting. Hydrogen production by water splitting produces no CO2 emissions if the electricity is generated from a renewable source (e.g. wind, solar)[1][2]. However, it must be efficient and cost-effective enough to compete with hydrogen production from steam reforming of fossil fuel sources [3]. The overpotential losses associated with driving the oxygen evolution reaction (OER) at the anode and the hydrogen evolution reaction (HER) at the cathode in both acidic and basic environments limit the efficiency of the water electrolysis system. In this context, the electrode materials play a key role in influencing the performance of the electrolyzers. Considerable efforts have been made in recent years to obtain highly efficient and inexpensive catalytic materials. In this work, Ni alloy nanowires with very high surface area and high electrocatalytic activity have been prepared by template electrosynthesis, which is a simple and cheap bottom-up method to obtain nanoscale materials [4][5][6]. To obtain different alloy compositions, the composition of the electrodeposition bath was varied by adjusting the concentration of metal precursors and by adjusting the electrodeposition parameters (current density and deposition time). Nanostructured electrodes were used to build a laboratory-scale water electrolyzer cell for hydrogen production. The electrolyzer has a zero-gap configuration, where the membrane is sandwiched between the anode and cathode to minimize the voltage drop between the electrodes. The laboratory-scale electrochemical cell was constructed by using a laser cutter. Electrolysis was performed in a 30% w/w KOH aqueous solution. Results obtained with nanostructured electrodes were compared using planar electrodes tested in identical conditions. Electrochemical and electrocatalytic characterizations were carried out to assess the properties of nanostructured alloys for both HER and OER in alkaline electrolyte. The effect of varying operating parameters on electrolyzer cell performance was evaluated through a series of experiments. The results showed that water-alkaline electrolyzers with nickel alloy nanowire electrodes exhibited good and stable performance at room temperature. Furthermore, the use of catalysts consistently improved performance over the range of current densities tested.