Overcoming humidity-induced swelling of graphene oxide-based hydrogen membranes using charge-compensating nanodiamonds

Graphene oxide (GO) can form ultrapermeable and ultraselective membranes that are promising for various gas separation applications, including hydrogen purification. However, GO films lose their attractive separation properties in humid conditions. Here we show that incorporating positively charged nanodiamonds (ND⁺s) into GO nanolaminates leads to humidity-resistant, yet high-performing, membranes. While native GO membranes fail at a single run, the GO/ND⁺ composite retains up to roughly 90% of GO’s H₂ selectivity against CO₂ after several cycles under an aggressive humidity test. The addition of negatively charged ND to GO brought no such stabilization, suggesting that charge compensation acts as the main mechanism conferring humidity resistance, where ND⁺s neutralize the negative charge GO sheets. We observed a similar but inferior stabilization effect when positively charged polyhedral oligomeric silsesquioxane replaces ND⁺. The demonstrated material platform offers a solution for separating H₂ gas from its usually humid mixtures generated from fossil fuel sources or water splitting.