Measurement and Modelling of Potential Profiles in Water Electrolysers to Minimize Titanium Use

Green hydrogen is an essential component of net zero strategies for ‘difficult to decarbonize’ sectors such as heavy duty transport, domestic heating and industrial processes, but its relatively high price remains a significant challenge. The cost of production using proton exchange membrane water electrolysers (PEMWEs) depends on both CAPEX of the devices and OPEX, which is dominated by the renewable electricity price. The latter is already low and is projected to continue to decrease so reducing CAPEX is the major focus of research efforts.<br/><br/>The assumption of a highly corrosive potential at the anode bipolar plate (BPP) and porous transport layer (PTL) in a PEMWE stack often leads to selection of expensive materials such as platinum-coated titanium. In this talk, a description will be given of a physicochemical model of electrochemical potential distribution in a PTL, validated by <i>in situ </i>and <i>ex situ</i> electrochemical potential measurement. The model predicts that, under typical PEMWE operating conditions, the corrosive zone associated with the anode polarisation extends only ≈ 200 µm into the PTL from the catalyst layer, removing the need for highly corrosion-resistant materials in the bulk of the PTL and at the BPP.<br/><br/>Guided by the model, single cell PEMWE tests were carried out using anode current collectors fabricated from carbon-coated 316L stainless steel. The material was shown to be tolerant to potentials up to 1.2 V vs RHE and when tested <i>in situ</i> for 30 days at 2 A cm^-2 showed no evidence of degradation. These results strongly suggest that much of the titanium in PEMWEs may be substituted with cheaper, more abundant materials with no loss of electrolyser performance or lifetime, which would significantly reduce the cost of green hydrogen. The combined modelling and experimental approach developed here shows great promise for design optimisation of PEMWEs and other electrochemical energy conversion devices.