Design and preparation of MoO₂/MoS₂ as negative electrode materials for supercapacitors

Highlights: • MoO₂/MoS₂ is successfully synthesized and is firstly served as negative electrodes for supercapacitors. • The MoO₂/MoS₂ electrode displays a high specific capacitance of 433.3 F g^-1 at a scan rate of 5 mV s^-1. • The MoO₂/MoS₂ electrode indicates higher specific capacitance than that of pure MoO₂ and pure MoS₂. • The capacitance retention of MoO₂/MoS₂ is 84.41% after 5000 cycles, which is superior to pure MoO₂ and pure MoS₂. In this work, the MoO₂/MoS₂ composite material with unique flower-like microsphere structure is prepared via a facile hydrothermal synthesis. Furthermore, the composite material is served as negative electrode for supercapacitors. Ascribe to the synergistic effect, including the improved electron conductivity, the coexistence of two energy storage mechanisms, and a stable flower-like microsphere structure, the as-fabricated MoO₂/MoS₂ exhibits a high specific capacitance of 433.3 F g⁻¹ at a scan rate of 5 mV s⁻¹ and a superior cycling stability of 84.41% retention after 5000 cycles compared to that of pure MoO₂ (33.33% retention after 2000 cycles) and pure MoS₂ (58.33% retention after 2000 cycles) at a current density of 1 A g⁻¹ in 1 M Na₂SO₄ electrolyte. Moreover, we also synthesize a series of MoO₂/MoS₂ electrode materials, which are used to further illustrate the synergistic effect in MoO₂/MoS₂ composite materials. This work signifies such materials as negative electrodes exhibit bright application prospects for supercapacitors.