Vanadium oxide is a promising pseudocapacitive electrode, but their capacitance, especially at high current densities, requires improvement for practical applications. Herein, a VO x @MoO 3 composite electrode is constructed through a facile electrochemical method. Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy demonstrate a modification on the chemical environment and electronic structure of VO x upon the effective interaction with the thin layer of MoO 3 . A careful investigation of the electrochemical impedance spectroscopy data reveals much enhanced power capability of the composite electrode. More charge storage sites will also be created at/near the heterogeneous interface. Due to those synergistic effects, the VO x @MoO 3 electrode shows excellent electrochemical performance. It provides a high capacitance of 1980 mF cm −2 at 2 mA cm −2 . Even at the high current density of 100 mA cm −2 , it still achieves 1166 mF cm −2 capacitance, which doubles the sum of single electrodes. The MoO 3 layer also helps to prevent VO x structure deformation, and 94% capacitance retention over 10 000 cycles is obtained for the composite electrode. This work demonstrates an effective strategy to induce interactions between heterogeneous components and enhance the electrochemical performance, which can also be applied to other pseudocapacitive electrode candidates.

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Electrochemical actuators play a key role in converting electrical energy to mechanical energy. However, a low actuation stress and an unsatisfied strain response rate strongly limit the extensive applications of the actuators. Here, we report hybrid manganese dioxide (MnO 2 ) fabricated by introducing ramsdellite (R-MnO 2 ) and Mn vacancies into birnessite (δ-MnO 2 ) nanosheets, which in situ grew on the surface of a nickel (Ni) film, forming a hybrid MnO 2 /Ni actuator. The actuator demonstrated a rapid strain response of 0.88% s −1 (5.3% intrinsic strain in 6 s) and a large actuation stress of 244 MPa owing to the special R-MnO 2 with a high density of sodium ion (Na + )-accessible lattice tunnels, Mn vacancies, and also a high Young's modulus of the hybrid MnO 2 /Ni composite. Besides, the cyclic stability of the actuator was realized after 1.2 × 10 4 cycles of electric stimulation under a frequency of 0.05 Hz. The finding of the novel hybrid MnO 2 /Ni actuator may provide a new strategy to maximize the actuating performance evidently through tailoring the lattice tunnel structure and introducing cation vacancies into electrochemical electrode materials.

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