Unlocking Stainless Steel’s Potential for the Hydrogen Evolution Reaction Using Patterned Electrodes
Authors: Tiffin Campbell Maurice , Khan Sami , Marshall Aaron Timothy 
Published: December 2024

The world's dependence on fossil fuels for transportation and power continues to contribute to anthropogenic climate change. However, fossil fuels are depletable resources and therefore a renewable fuel and energy source is needed in the immediate future [1]. Hydrogen is an ideal candidate to replace fossil fuels. Energy can be stored in hydrogen bonds and released as electricity by hydrogen fuel cells, creating only heat and water in the process [2]. Traditionally, hydrogen is produced from steam methane reforming and coal gasification, where carbon dioxide is generated in tandem [3]. Therefore, a renewable method to produce hydrogen is needed. Hydrogen can be produced with zero carbon emissions in water electrolysis, provided the electricity used is renewable, e.g. wind, solar, hydro.

Currently, the widespread application of water electrolysers is limited by the sluggish kinetics of the oxygen/hydrogen evolution reactions (OER and HER, respectively) that require large overpotentials and complex multistep proton-coupled electron transfer processes, thus limiting the overall efficiency. Efficient electrodes for water electrolysis are based on expensive and scarce platinum group metals, further limiting the widespread application of water electrolysis [4]. Ideally, water electrolysis electrodes should have high corrosion resistance, conductivity, catalytic activity, and surface area while being low-cost, widely available and scalable. Alkaline water electrolysis allows for non-noble, low-cost, transition metal oxides to be used as they are relatively stable thermodynamically compared to acidic environments [5]. Recently, Ni-Fe layered double hydroxides were shown to have high electrocatalytic activity and stability for the OER in alkaline conditions [6]. This led to a series of studies on optimising the activity of stainless steel, owing to it being an alloy predominantly composed of Fe and Ni while being low cost, widely available and having excellent corrosion resistance.

In this research, we utilise laser surface texturing, a scalable, efficient and widely used technique to modify surface area and morphology [7]. We create microchannel arrays with 20 µm channels spaced 10-200 µm apart on stainless steel 304 (SS304), thus systematically increasing the electrodes’ surface area. The electrode performance for the OER/HER was evaluated by slow linear sweep voltammetry in a 3-electrode cell containing 1 M KOH. Results show that the HER performance is strongly influenced by surface area and morphology while OER is relatively unimpacted (Figure 1). Scanning electron microscopy (SEM) coupled with energy dispersive spectroscopy and cyclic voltammetry suggests the performance is not a result of modification of the surface composition. Tafel slope analysis shows that all textured electrodes have similar Tafel slopes to the planar electrodes, indicating that the texturing does not affect the rate-determining step revealing that increasing surface area is key to unlocking stainless steel’s potential for the HER.

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Figure 1