ONIOM Study on the Influence of Aluminium in Propylsulfonic Acid‐functionalized ZSM‐5 for Proton Transfer

Abstract Proton exchange membrane fuel cells (PEMFCs) are promising candidates for clean and efficient power sources. Zeolite nanoparticle membranes have been introduced as potential new membrane materials to improve the performance of PEMFCs. Understanding the proton transport mechanism on zeolite nanoparticle membranes at the atomic level is crucial in developing more efficient PEMFCs. We investigated the influence of aluminium to initiate proton transfer within zeolite fragments by performing geometry conformation of hydrated propylsulfonic acid‐functionalized zeolite ZSM‐5 clusters from one to six water molecules using four different ONIOM schemes; ONIOM(B3LYP:HF) and ONIOM(B3LYP:PM3) in gas phase and within polarizable continuum model (PCM) of water system. Results show that four water molecules are required for second proton dissociation to occur in Al systems, whereas at least five water molecules are needed in their counterpart systems. Analysis of the results suggests that the presence of Al atom in the zeolite backbone increases the electronegativity of the oxygen atom of the sulfonic acid. The oxygen provides an active site for the acidic proton to participate and increased the ability of hydrogen to dissociate itself and form hydronium cations. Our ONIOM calculation proves that ONIOM(B3LYP:PM3) method of calculation provides a reliable result with minimal computational cost.