The key to carbon-neutral, green hydrogen production is proton exchange membrane (PEM) electrolysers, which use electrolysis to extract hydrogen as either a liquid or gas, central to this is the porous transport layer (PTL). Titanium is considered the optimal material for the PTL due to its unique balance of corrosion resistant properties (at low pH and high voltage anodic conditions) and relatively low material/processing cost vs. precious metal alternatives such as platinum. However, the cost of titanium is still a barrier to adoption of PEM technology.
Using low energy intensity titanium powder feedstocks, including both “recycled” hydride-de-hydride (HDH) Ti-6Al-4V and as-Kroll extracted titanium sponge fines (CP-Ti sponge) could reduce the cost of these components, especially when combined with efficient production processes like Field Assisted Sintering Technology (FAST). Titanium powder can be blended with salts like sodium chloride (NaCl), sintered using FAST, then the salt dissolved away to leave a porous titanium plate.
The combination of these factors allows both the financial and environmental costs of using manufactured titanium parts to be greatly reduced. This has the potential to accelerate the uptake of carbon-neutral green hydrogen energy production, making it a widely financially viable, clean energy solution.
Under the instruction of the Manufacturing Technology Centre (MTC), Dr Simon Graham and Nigel Adams used the FCT-HPD25 FAST equipment at the Royce Discovery Centre at the University of Sheffield to successfully produce porous titanium plates.
By blending titanium powder and innovative NaCl salt-based space holding inserts, they produced complex titanium bipolar plates with an intricate internal flow field channel and integrated porous transport layer. Additionally, this method was more rapid than Hot Isostatic Pressing (HIP) due to the higher heating rates and shorter dwell times required.
The demonstrators were used to showcase the potential of this new manufacturing route in reducing both the capital cost (CapEx) and operating efficiency cost (OpEx) of a large and high performance PEM electrolyser stack.
Additionally, low energy intensity powder materials, including both “recycled” hydride-de-hydride (HDH) Ti-6Al-4V and as-Kroll extracted titanium sponge fines (CP-Ti sponge) were evaluated and proven to consolidate effectively. Showing that alternative, circular economy methods are possible for processing titanium into complex hydrogen electrolyser components at a viable cost with sustainability benefits.