We show high activity in non-nitrogen doped and non-metal electrocatalysts based on carbon nanotubes with onset potential up to 0.73 V vs. RHE by the formation of hole defects on the walls of carbon nanotubes, followed by annealing under Ar atmosphere. From the power generation test, this catalyst can deliver a maximum output power of 55.68 mW (mg⁻¹ _{CNT cathode}). Through temperature programmed desorption (TPD) and electrochemical analysis, the creation of new active sites is correlated with the removal of high temperature CO desorbing functionalities. Residual metal impurities were examined by the use of inductively coupled plasma-mass spectroscopy (ICP-MS), high angle annular dark-field (HAADF) and electron energy loss (EELS) analysis. The extremely low amount of metal impurities and the absence of impurity coordination at the edge planes after electrochemical characterization suggest that it is unlikely that impurities directly contribute to ORR. We conclude by proposing that the origin of ORR activity is a result of carbon restructuring and the possible formation of topological defects during the removal of high temperature CO desorbing functional groups.

Nano-drilling of multiwalled carbon nanotubes (MWCNTs) has been conducted by taking advantage of CoO_x as the oxidation catalyst at a relatively low temperature of 250 °C. An increase of the I_D/I_G ratio of Raman spectroscopy, together with TEM visualization, justifies the presence of hole defects on the sidewalls, in comparison to the pristine and purified MWCNTs. Holes drilled on the basal plane of MWCNTs could increase access into the inner core as observed by the N₂ adsorption isotherm. Drilled MWCNTs (DMWCNTs) show the largest quantity of functional groups of 5.4 × 10⁻³ mol g⁻¹, which suggests that our drilling method also introduces functional groups on the edges. We also tested the electrochemical performance of our MWCNT samples as the anode material for lithium ion batteries. After 20 cycles at a current density of 25 mA h g⁻¹, the specific discharge capacities of pristine, purified and DMWCNTs are 267, 421 and 625 mA h g⁻¹, respectively. DMWCNTs exhibit the largest quantity of Li extraction from the GIC and inner core as shown by the dQ/dV discharge profiles. This suggests that increased access into the MWCNT inner core is proven to have positive effects on Li storage properties.

Off-stoichiometric CuInS₂ quantum dots (CuInS₂, a mixture of In₂S₃/CuInS₂, and a Mn-doped mixture of In₂S₃/CuInS₂) were prepared in a one-pot reaction, and the corresponding sensitized solar cells exhibit promising photovoltaic performances.

Perovskite solar cells (PSCs) have attracted a lot of interest because of their high efficiency and low cost. However, in commercial applications, standard PSCs suffer from low stability of the cell components, including the hole transportation material (HTM). Owing to their characteristics of high chemical stability, hydrophobicity, and high conductivity, carbon nanotubes (CNTs) can be an alternative electrode to use to form HTM‐free PSCs. Enhancing the interaction with perovskite is vital not only for photovoltaic performance but also for the stability of CNT‐based PSCs. Herein, oxygen‐containing functional groups are introduced into CNTs via acid treatment to enhance the chemical interactions with perovskite. The self‐recrystallization ability of the perovskite material is discovered; its morphology shows significant improvement after long‐term storage. Results show that acid oxidization of CNTs enable the self‐recrystallization characteristics of MAPbI₃‐induced interfacial improvement, such that even with a dispersed initial photovoltaic performance, through storage in an ambient medium with relative humidity of 20–50%, the PSCs possess better interface contact, which results in lower charge transfer resistance, higher photovoltaic performance, and stability. As a result, PSCs with an initial power conversion efficiency range of 3.21–7.89% finally converge to within the range of 9.54–12.14% after long‐term storage.

Self‐Recrystallization In article number 1900302, Keiko Waki and co‐workers discover the ability of functionalized carbon nanotubes to make use of the self‐recrystallization nature of perovskites. As...