Mitigating methanol crossover using Pt–Ru catalyst coated on commercial membrane of ethanesulfonyl fluoride through layer-by-layer technique

Abstract

In this study, 10 bilayers of poly (allylamine hydrochloride) (PAH)/polystyrene sulfonic acid sodium salt (PSS) with Pt47–Ru53 catalyst are self-assembled on both sides of the commercial membrane of ethanesulfonyl fluoride via layer-by-layer technique to mitigate methanol crossover. The Pt47–Ru53 alloy catalyst is dispersed in the PAH/PSS bi-layers through the reduction of the Pt and Ru ions in the PSS. Experimental results show that the Pt47–Ru53 catalyst with an average particle size of 5nm and a layer thickness of 1.31μm, which is similar to the thickness of 10 PAH/PSS bi-layers, is coated onto both sides of the commercial membrane of ethanesulfonyl fluoride. Compared to untreated commercial membrane of ethanesulfonyl fluoride at 60°C, this composite membrane, with Pt47–Ru53 loading of 16.5μgcm−2, suppresses methanol crossover by 12% (on average) and improves output voltage and power density by 18% and 46% (@79mAcm−2), respectively. The Pt47–Ru53 catalyst in the PAH/PSS bi-layers oxidizes the crossed-over methanol and produces extra current. It also reduces the mixed potential effect in the cathode. The 10 PAH/PSS bi-layers with low methanol permeability function like a methanol barrier, blocking the crossed-over methanol. Combining these effects, the self-assembly of the PAH/PSS containing Pt47–Ru53 alloy onto the commercial membrane of ethanesulfonyl fluoride can effectively improve output voltage and power density and can suppress methanol crossover.