Hierarchical porous carbon supported NixCo1−xMoO4 nanoparticles: A high-performance electrode for asymmetric supercapacitors

Transition-metal molybdate (MMoO4) compounds have recently garnered considerable attention as an electrode material with very broad application prospects, owing to their exceptional electrochemical properties. In this study, we present the successful in-situ synthesis of NixCo1−xMoO4 bimetallic nanoparticles on a three-dimensional hierarchical porous carbon (HPC) derived from enzymatic-hydrolysis lignin. The potential of the resulting HPC/Ni0.75Co0.25MoO4 composite as a positive electrode material for asymmetric supercapacitors was thoroughly investigated. By carefully tuning the composition of the HPC/Ni0.75Co0.25MoO4 material in terms of the Ni/Co ratio and HPC content, the electrochemical performance was optimized at multiple scales. The unique nanostructure and synergistic effects among various components of the HPC/Ni0.75Co0.25MoO4 composite electrode are the key factors that contribute to its exceptional electrochemical performance. The nanostructure provides more active sites for the electrode, which improves the ion and electron transport. As a result, the HPC/Ni0.75Co0.25MoO4 composite electrode displayed an outstanding specific capacitance of 1626.2 F g−1 (813.1C g−1) at a current density of 1 A g−1, attributed to the distinctive nanostructure and strong synergistic effects among various components. The synergistic effects among various components enhance the electrochemical reactivity of the electrode, further improving its capacitance performance. Density functional theory calculations support the improved conductivity of NixCo1−xMoO4, which provides theoretical evidence for the high specific capacitance of the composite electrode. The calculations show that the doping of Ni and Co can improve the conductivity of MoO4, resulting in an increase in the electrode's specific capacitance. The assembled asymmetric supercapacitor based on the HPC/Ni0.75Co0.25MoO4 electrode delivers a high energy density of 82.2 W h kg−1 at a power density of 800 W kg−1. The wide voltage window of 1.6 V indicates its broad applicability in real-world scenarios. Notably, the device demonstrated exceptional stability, retaining 85.14 % of its capacitance after 10,000 cycles. The rational design of the HPC/Ni0.75Co0.25MoO4 composite provide outstanding train of thought for the development of high-performance bimetallic oxide materials. This research has great potential for energy-related applications, offering new avenues for synthesis and innovation in the field.