Ultrafine Ag/MnO_x nanowire-constructed hair-like nanoarchitecture: In situ synthesis, formation mechanism and its supercapacitive property

Graphical abstract: In this work, novel hair-like (HL) nanoarchitectures constructed by ultrafine MnO_x nanowires (∼7 nm) entrapped with Ag nanoparticle were first synthesized by facile in situ reaction between Ag nanowires and KMnO₄, and a following hydrothermal method. The as-prepared HL Ag/MnO_x nanocomposites as electrode delivered a high specific capacitance and good cycle stability. - Highlights: • Ultrafine MnO_x nanowires with Ag nanoparticle dispersed on were in situ prepared. • Kirkendall effect and Ostwald ripening mechanism ascribed to developed morphology. • Desirable specific capacitance and cyclability made it candidate for supercapacitors. - Abstract: Hair-like (HL) nanoarchitectures constructed by ultrafine MnO_x nanowires (∼7 nm) with ultrafine Ag nanoparticles anchored on were synthesized by in situ facile reaction between silver (Ag) nanowires and potassium permanganate (KMnO₄), and followed by a following hydrothermal method. Based on a serious of time-dependent experiments, an orderly merged Kirkendall effect and dissolution-recrystallization (Ostwald ripening) mechanism were proposed for the formation of this novel morphology. The as-prepared HL Ag/MnO_x nanocomposites as electrode exhibited a high specific capacitance (526 Fg⁻¹ at scan rate of 5 mV s⁻¹ and 450 Fg⁻¹ at current density of 0.1 Ag⁻¹), good rate capability (ca. 45.5% retention with reference to 205 Fg⁻¹ at 50 times higher current density of 5 Ag⁻¹) and desirable cycle stability (ranging from initial of 237 Fg⁻¹ to 185 Fg⁻¹ after 800 cycles and still maintaining 87% retention compared to 800th cycle after another 2800 cycles at current density of 2 Ag⁻¹). Such desirable performance could be attributed to HL Ag/MnO_x nanocomposites core (tubular nanosheets) with uniform dispersion of the ultrafine Ag nanoparticals provides a direct pathway for electron transport while the partial connected ultrafine nanowires networks with high specific surface area provides more electronic transmission channels and easy permeation of electrolyte, decreasing the polarization of the electrode and thus enhancing the discharge capacity and high-rate capability