Anion-exchange membrane water electrolysers are a promising approach to generate hydrogen, allowing the use of relatively cheap components and high-operating pressures; yet performance enhancements are still needed to make them competitive with alternative technologies. One way to boost performance is to move from flat sheet membranes to those with patterned surfaces; the microscale features can enhance mass transfer and catalyst utilization. Simple, tuneable, sustainable approaches would be particularly desirable. Now, Young Moo Lee and colleagues at Hanyang University, Korea Institute of Science and Technology and Xiamen University report a facile method to fabricate anion-exchange membranes with rough surfaces using reusable silicon templates, ultimately leading to improved electrolyser performance.
To make the membranes, the researchers cast a solution of poly(dibenzyl-co-terphenyl piperidinium) onto a commercial silicon plate that has pyramidal surface features with an average width of 2.5 µm. The surface pattern of the plate — which in principle could be tuned by controlled etching — is transferred to the cast membrane, and the template can be cleaned and re-used. Subsequently, catalysts are sprayed onto the membrane to coat the surface. The team find that patterning the membrane leads to 39% better water permeability and 23% better electrochemical surface area than the flat counterpart. They attribute this improvement to higher contact areas of water and catalyst, respectively, with the rough membrane surface. Using PtRu as the cathodic catalyst and a non-precious metal catalyst at the anode, the electrolyser achieves a high current density of 14.4 A cm–2 at 2 V and 80 °C in 1 M NaOH.
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