We designed a novel multiphase Fe-doped MnO₂ electrolyte material for supercapacitors. The synergistic effects of the alternative crystal structures, appropriate crystallinity and optimal morphology are identified to be responsible for the boosted pseudocapacitive performances.

The oxygen adsorption can drastically alter the electronic properties of the 2D materials, which is usually difficult to be removed. In this work, we report the UV illumination induced desorption of the O₂ molecules from the monolayer MoS₂ surface by using the atmosphere dependent transport measurement, Kelvin probe microscopy, photoluminescence spectroscopy and X-ray photoelectron spectroscopy. Obvious increasing of the conductivity, rising of the Fermi level, and red shift of the photoluminescence peaks of the MoS₂ were observed after the UV illumination in vacuum, indicating the elimination of the depletion effect from the oxygen adsorption. Such parameter changes can be reversibly recovered by the subsequent O₂ exposure. Furthermore, obvious decreasing of the oxygen concentration after the UV illumination was also observed by X-ray photoelectron spectroscopy. Thus the UV induced O₂ photodesorption effect is evidenced. The photo-excited charge transfer mechanism is proposed to account for the photodesorption effect. These results provide a nondestructive way to clean the MoS₂ surface and manipulate the performance of the MoS₂ based devices.