Synergistic engineering of MoB/Ni3S2 heterostructures in asymmetric supercapacitors for high-performance alternating current line filtering

Asymmetric supercapacitors (APCs) for AC line filtering offer extended operating voltages and enhanced energy density by coupling two dissimilar electrode materials. This study, presents a high-performance filtering APC constructed from two-dimensional layered MoB (an MBene) as the negative electrode and in-situ grown, porous Ni 3 S 2 as the positive electrode. The unique synergy between the conductive layered MoB and the vertically arranged pseudocapacitive Ni 3 S 2 nanoarchitecture can achieve rapid on/electron transport, yielding a high specific surface area capacitance of 760 μF cm −2 , a negative phase angle of 50.9° at 120 Hz, and a resistance-capacitance time constant (τ RC ) of 1.05 ms. On this basis, increasing the KOH concentration to 10 M further expands the voltage window to 0.9 V due to enhanced electrolyte conductivity and irreversible interfacial side reactions. To further enhance cycling stability and rate performance, a composite electrode integrating few-layer MoB with Ni 3 S 2 in a nanoflower morphology was designed. This optimized composite increases accessible active sites and strengthens interfacial charge transfer, boosting The 120 Hz specific capacitance to 834 μF cm −2 , raising the negative phase angle to 55°, and shortening τ RC to 0.19 ms. The work demonstrates a rational materials-design strategy that combines MBenes with transition-metal sulfides, providing both mechanistic insight and a practical route to compact, high-voltage, and ultrafast AC-filtering devices.