Constructing hollow cobalt sulfide nanocages strung by manganese molybdate nanorods for high-efficiency supercapacitors and electrocatalytic methanol oxidation

Constructing core-shell heterostuctures with rationally designed nanoarchitectures and components is a promising strategy to pursuit high-efficiency energy storage and conversion in supercapacitors (SCs) and direct methanol fuel cells (DMFCs). Herein, a multi-dimensional MnMoO₄@CoS core-shell heterostructure is designed and synthesized by stringing metal-organic framework-derived hollow CoS nanocages with MnMoO₄ nanorods. Such heterostructure provides more electroactive sites and enhanced structural stability. Theory calculations unveil that the work function difference between MnMoO₄ and CoS induces the charge redistribution and modulate interfacial electronic configuration in the MnMoO₄/CoS heterojunction. Meanwhile, a interfacial built-in electrical field is established, enhancing interfacial charge transfer efficiency and promoting the surface adsorption of electrolyte ions. By integrating all these advantages, the MnMoO₄@CoS electrode demonstrates enhanced rate capacities (933 C g⁻¹ at 1 A g⁻¹ and 623 C g⁻¹ at 10 A g⁻¹) and cycling durability (90.3 % capacity retention after 10,000 cycles) compared to bare MnMoO₄ and CoS electrodes. Moreover, the MnMoO₄@CoS electrode exhibits an appreciable electrocatalytic performance for methanol oxidation, with a current density of 294.8 mA cm⁻² at 10 mV s⁻¹ and 96.6 % current retention after 10,000 s. Our work offers a fundamental guideline for designing and engineering core-shell heterostructures with desirable electrochemical performance for SCs and DMFCs.