Benchmarking Protocols for Proton Exchange Membrane Water Electrolyser
A reliable electrochemical evaluation protocols to assess the performance of the fabricated CCMs were also developed. Several operating test parameters were investigated, where it was found that a compression of 4 kN and a water flow rate of 0.1 L/min provided better temperature control and improved overall CCM performance. Furthermore, from the porous transport layer (PTL) investigation, it was found that titanium powder sintered PTLs on both the anode and cathode sides provided a better overall electrolyser cell performance at iii high current density operation. Also investigated, were the effects of different electrolyser cell conditioning and evaluation measurement parameters on the overall CCM performance and it was found that the shortest cell conditioning time of 5 min provided the lower performance while cell conditioning times of 15 min, 30 min and 45 min showed no significant differences in their results. The addition of the open circuit voltage (OCV) step and the halving of the current-voltage measurement interval time from 5 min to 2.5 min provided the best CCM performance and improved significantly the cell performance profile at 1000 mA cm-2 over time.
Also, the effect of pore forming additives to the anode catalyst ink on the anode catalyst layer morphology and overall PEMWE cell performance was investigated. Ammonium carbonate and ammonium bicarbonate with varying weight ratios were used as pore forming additives in the catalyst ink formulation and subsequently removed during the decal transfer process. The investigation was conducted on both Nafion 212 and Nafion 115 membranes. From the investigation of pore forming additives effects, the physical characterisation of the anode catalyst layers data showed that an increase of porosity (pore size, pore quantity and pore distribution) in the anode catalyst layer was achieved in this study. The addition of pore forming substances increased the quantity of pores in the catalyst layer. The electrochemical performance evaluation of the PEMWE cell showed that the addition of pore forming additives to the anode electrode catalyst ink formulation allowed for the reduction of iridium catalyst loading while improving the electrochemical performance. The iridium catalyst loading reduction of up to 45% was achived while improving the overall cell perfomance. Furthermore, the electrochemical evaluation tests showed that the CCMs with a high number of pores in their catalyst layers had the best catalyst utilisation compared to CCMs without pore formers.