Ionically selective carbon nanotubes for hydrogen electrocatalysis in the hydrogen–bromine redox flow battery

Catalyst poisoning and leaching is a problem faced in almost all catalyst applications. A specific technology where catalyst poisoning and leaching are a major concern is the hydrogen bromine redox flow battery (H₂–Br₂ RFB), one of the most promising energy storage technologies. However, it is currently hindered through degradation of the hydrogen oxidation/evolution catalyst, caused by Br⁻/Br₃⁻ which have crossed the membrane. To prevent this degradation, Pt nanoparticles were synthesized inside 2 nm single-walled carbon nanotubes (SWCNTs). Electrochemical and spectroscopic techniques show that the Pt@SWCNT has a vastly improved stability and higher mass activity over a commercial 50% Pt/C catalyst. Density functional theory (DFT) calculations show that the stability results from the selective diffusion of H₂ and H⁺ over the Br⁻ and Br₃⁻ species through the SWCNT to the Pt catalyst, effectively protecting Pt from oxidative leaching.