Mn and S-doped nickel molybdate/nickel molybdate hydrate micro-structures for supercapacitor applications

Abstract

Scientific community is still attempting to understand the synergistic interaction between heteroatom doping and the design of rational heterostructured metal oxides. This is a significant and efficient method for constructing high-capacity electrochemical energy storage systems. In the present work, manganese (Mn) and sulfur (S) are co-doped precisely into nickel molybdate and nickel molybdate-hydrate (Mn-S-NiMoO₄/NiMoO₄⋅xH₂O@NF denoted as Mn-S-NMO) using a novel chemical approach for ameliorating the charge storage kinetics. The Mn-S-NMO electrode demonstrated a higher specific capacitance of 10758.75F g⁻¹ at 6 A g⁻¹ compared to undoped NMO (2280F g⁻¹ at 6 A g⁻¹) electrode, which is one of the highest reported values for metal oxides to date. This remarkable performance is attributed to its unique crystal structure, the collaboration of dual-ion dopants, interfacial synergistic modifications, the presence of multi-valent ions, defined oxygen vacancies, improved conductivity, increased active sites, rapid ion diffusion and electron transfer, superior higher specific capacitance, charge-transfer efficiency, and reliable cycling stability. Moreover, a symmetric supercapacitor having Mn-S-NMO//Mn-S-NMO configuration achieves an energy/power density of 52.4 Wh kg⁻¹//2100 W kg⁻¹ also demonstrates durable redox cycle life with 88.7 % even after 20000 redox cycles attempted at an excessive current density of 15 Ag⁻¹. The as-obtained symmetric supercapacitor, with two devices in series, has successfully powered a “CNED” colorful panel with 42 LEDs at full brightness for 10 min, demonstrating, by synergistic modulating, the practical significance and scientific merits of the heteroatom-doped hydrated nickel molybdate electrode for real-world commercial appliances.