Interfacial-coupling-driven 2D Ni(OH)2/SnO2 hybrid heterostructures for carbon-free, durable supercapacitor electrodes

Low-cost, carbon-free electrodes that stay stable over long cycling are hard to make without conductive scaffolds such as graphene or carbon nanotubes. We report 2D Ni(OH) 2 /SnO 2 hybrid nanostructures prepared by a single-step hydrothermal route, in which ultrathin β-Ni(OH) 2 nanosheets grow on SnO 2 nanoparticles. XRD shows no peak shift, so the two phases form a heterointerface without lattice substitution. In a three-electrode cell in 1 M KOH, cyclic voltammetry and galvanostatic charge–discharge give consistent capacitances when both are referred to the same active mass: bare Ni(OH) 2 reaches 127 F g −1 (CV) and 97.8 F g −1 (GCD, 0.31 A g −1 ), while the SnO 2 /Ni(OH) 2 composite gives 39 F g −1 by both methods. The composite does not exceed bare Ni(OH) 2 in gravimetric capacitance; its advantage is durability, holding 92.6% of its initial capacitance after 6000 cycles. Impedance analysis returns a low, similar solution resistance (R s ≈ 0.9–1.0 Ω) for all three electrodes, with the charge-transfer resistance not resolvable within the measured frequency window. Oxide–hydroxide coupling without lattice substitution gives a stable, carbon-free electrode; we report the CV- and GCD-derived capacitances on a common basis rather than a record value.