The protonated 2 × 4 tunnel manganese oxide nanobelts for high-efficient electrochemical rubidium enrichment

Octahedral molecular sieve – 5 (OMS-5), a typical 2 × 4 tunnel manganese oxide, is considered as an adsorbent for rubidium ion (Rb+) because of its specific tunnel structure. Also, manganese oxide-based nanomaterials are also widely used in supercapacitor energy storage and capacitor deionization electrodes due to their high specific capacitance. In this work, a series of protonated OMS-5 (H-OMS-5, H-Co-OMS-5, and H-Ni-OMS-5) nanobelts are synthesized and used as electrode materials for electrochemical enrichment of Rb+ in aqueous solution. The specific capacity values for H-OMS-5, H-Co-OMS-5, and H-Ni-OMS-5 at 1 A·g−1 are of 159, 168, and 215 F·g−1, respectively. Thanks to the unique protonated 2 × 4 tunnel structure, well regulating surface area, and excellent specific capacitance, the maximum Rb+ adsorption capacities of H-OMS-5, H-Co-OMS-5, and H-Ni-OMS-5 can reach to 390.3, 405.7, and 481.7 mg·g−1, respectively. These results indicate that the protonated 2 × 4 tunnel manganese dioxide nanobelts are of great potentials as faradaic electrode materials for selective rubidium ion enrichment applications.