Ni and Cu ion-exchanged nanostructured mesoporous zeolite: a noble metal free, efficient, and durable electrocatalyst for alkaline methanol oxidation reaction

Abstract

The direct methanol fuel cell (DMFC) is considered as one of the promising power hubs to ensure the future global energy demand. The development of an efficient and cost-effective electrocatalyst for methanol electrooxidation (MEO) is one of the keys to make DMFC viable for practical application. Herein, an effort has been made to design a low-cost, noble metal free MEO catalyst. The electrocatalyst is synthesized by a facile ion-exchange of mesoporous zeolite ZSM-5 (Zeolite Socony Mobil 5) with non-precious Ni2+ and Cu2+ ions. The detailed electrocatalytic investigations reveal that the optimum contents of Ni2+ and Cu2+ ions in ion-exchanged mesoporous ZSM-5 (Ni2Cu1-MesoZ) are required to exhibit the best electrocatalytic activity (current density and onset potential). Moreover, the MEO capacity of the developed catalyst is found to be comparatively higher than the state-of-art Pt (20%)/C catalyst. The present electrocatalyst retains the catalytic current density even after 1000 cycles of a test run without any micro-structural change. The high surface area, Brönsted acidity, abundant surface hydroxyl groups, inter-crystalline mesoporosity, effective & optimum incorporation of Ni2+/Cu2+ species in the zeolite matrix provide highly dispersed electroactive sites and fast analyte diffusion resulting in a noteworthy MEO kinetics. The CO-stripping analysis also indicates that Ni2Cu1-MesoZ has a high tolerance to CO poisoning which is one of the prime reasons for high MEO activity. The underlying results demonstrate that the impressive electrocatalytic activity and high stability of Ni2+-Cu2+ ion-exchanged mesoporous ZSM-5 would be an interesting electrode material for the commercial methanol fuel cell application. Most importantly, the present study will open up a new avenue in the MEO electrocatalyst development due to its ease of synthesis, scale-up, fabrication, stability/durability, and efficient electrocatalytic activity for alkaline direct methanol fuel cell.