Energy Efficiency Improvement of Alkaline WaterElectrolysis by using 3D Ni Cathodes Fabricated via a Double-Template Electrochemical Process

Energy Efficiency Improvement of Alkaline WaterElectrolysis by using 3D Ni Cathodes Fabricated via a Double-Template Electrochemical Process

Alkaline water electrolysis is one of the easiest methods for hydrogen production, offering the advantage ofs implicity. Moreover, it represents an environmentally friendly technology for production of high purityh ydrogen. Nevertheless, the elevated production costs due to low conversion efficiency and electricalp ower expenses can be named as the main drawbacks of electrochemical hydrogen production.

This work is focused on the development and characterization of 3D porous Ni cathodes for alkalinee Electrolyzers. The electrodes were synthesized by nickel electrodeposition on copper foams obtained fromh ydrogen bubbles dynamic templates (double-template electrochemical process). The developed electrodes were characterized by SEM, confocal laser scanning microscopy, and EDX. The electrocatalytic performance of the developed electrodes for hydrogen evolution reaction (HER) was evaluated in 30 wt.%

KOH solution by using hydrogen discharge curves and galvanostatic tests. Results show that the use oft he developed electrodes as cathodes in electrolysis systems makes possible an energy saving of ca. 25% in conditions at which industrial alkaline water electrolysis is carried out, in comparison with the smooth commercial Ni electrodes.

1. Introduction

Hydrogen is considered an ideal energy carrier that can be an alternative to fossil fuels due to the fact that hydrogen is a clean and fully recyclable substance with a practically unlimited supply (Kunzru, 2008). The electrochemical production of hydrogen by alkaline water electrolysis is one of the most promising methods with great potential of using renewable energy sources (Miltner et al., 2009). Furthermore, it represents an environmentally friendly technology for production of high purity hydrogen (Veziroglu et al.,1992). However, the high energy consumption of alkaline water electrolyzers retrains its large-scaleapplication at present.

Although platinum shows the highest activity for the hydrogen evolution reaction (HER), new electrode materials have been investigated, aiming at the reduction of the cost associated with the electrocatalyst

development. Among these materials, nickel and its alloys show a high initial electrocatalytic activity

toward the HER. The electrode activity can be enlarged by increasing the real surface area and/or the

intrinsic activity of the electrode material (Lasia, 2003).

The increase of the real surface area can be achieved by several methods: depositing Ni together with an

active metal like Al or Zn (i.e. by electrodeposition, thermal spray, etc.) followed by the dissolution of the

secondary component (Raney type electrodes); electrodeposition of Ni at large current densities,

electrodeposition of Ni on metallic opals (made of silica or polystyrene) with proper porosities and

layer/thickness, followed by a selective removal of the opal. As a result, a porous, three-dimensional (3D)

structure is obtained, characterized by a high surface roughness factor, Rf.

In our previous work (Herraiz-Cardona et al., 2012), different electrode materials were prepared by means

of a double electrochemical template technique, consisting of the nickel coating of metallic foams obtained