Potassium‐ion batteries (PIBs), using carbon materials as the anode, are regarded as a promising alternative to lithium‐ion batteries owing to the feasible formation of stage‐1 potassium intercalation compounds (KC8). However, due to the large radius of the potassium ion, graphite‐based electrodes still suffer poor rate capability and insufficient cycling life. In this work, a hierarchically nitrogen‐doped porous carbon (NPC) is reported for the first time. The NPC electrode delivers a high reversible capacity of 384.2 mAh g−1 after 500 cycles at a current density of 0.1 A g−1 and an outstanding rate capability of 185 mAh g−1 at 10.0 A g−1, which surpasses most of the reported carbonaceous electrodes in PIBs. The excellent performance can be ascribed to the surface‐driven behavior dominated K‐storage mechanism, which is verified by quantitative kinetics analysis. Theoretical simulation results further illuminate the enhanced K affinity in N‐doped active sites, which accounts for the superior rate performance of the NPC electrode. In addition, galvanostatic intermittent titration technique measurements further quantify the diffusion coefficient of K ions. Considering the superior electrochemical performance of the electrode and comprehensive investigation of the K storage mechanism, this work can provide fundamental references for the subsequent research of potassium‐ion batteries.

Graphene-like two-dimensional layered materials have attracted quite a lot of interest because of their sizable band gaps and potential applications. In this work, monodisperse tin disulfide (SnS2) nanosheets were successfully prepared by a simple solvothermal procedure in the presence of polyvinylpyrrolidone (PVP). Large PVP molecules absorbing on (001) facets of SnS2 would inhibit crystal growth along [001] orientation and protect the product from agglomeration. The obtained SnS2 nanosheets have diameters of ca. 0.8-1 μm and thicknesses of ca. 22 nm. Different experiment parameters were carried out to investigate the transformation of phase and morphology. The formation mechanism was proposed according to the time-dependent experiments. SnS2 nanosheets exhibit high photocatalytic H2 evolution activity of 1.06 mmol h(-1) g(-1) under simulated sunlight irradiation, much higher than that of SnS2 with different morphologies and P25-TiO2. Moreover, the as-obtained SnS2 nanosheets show excellent photoelectrochemical response performance in visible-light region.

We report the interlayer screening effects of ultrathin MoS2 nanoflakes with different thicknesses by measuring their surface potential using Kelvin probe microscope. Surface potential of pristine MoS2 nanoflakes decreased with increasing thickness, while after annealing, the trend was opposite and the screening length became smaller. These results were qualitatively explained by a charge transfer model with the built-in electric field induced by trapped charges. The transport mechanism of MoS2 nanoflakes with different thicknesses was also studied by using conductive atomic force microscopy, and the thermonic emission and Fowler-Nordheim tunneling were effective in the forward bias and reverse bias, respectively.

Theranostic agents for magnetic resonance imaging (MRI) guided photothermal therapy have attracted intensive interest in cancer diagnosis and treatment. However, the development of biocompatible theranostic agents with high photothermal conversion efficiency and good MRI contrast effect remains a challenge. Herein, PEGylated Mn2+-chelated polydopamine (PMPDA) nanoparticles were successfully developed as novel theranostic agents for simultaneous MRI signal enhancement and photothermal ablation of cancer cells, based on intrinsic manganese-chelating properties and strong near-infrared absorption of polydopamine nanomaterials. The obtained PMPDA nanoparticles showed significant MRI signal enhancement for both in vitro and in vivo imaging. Highly effective photothermal ablation of HeLa cells exposed to PMPDA nanoparticles was then achieved upon laser irradiation for 10 min. Furthermore, the excellent biocompatibility of PMPDA nanoparticles, because of the use of Mn2+ ions as diagnostic agents and biocompatible polydopamine as photothermal agents, was confirmed by a standard MTT assay. Therefore, the developed PMPDA nanoparticles could be used as a promising theranostic agent for MRI-guided photothermal therapy of cancer cells.

We report the strong catalyst–support interaction in WC‐supported RuO2 nanoparticles (RuO2‐WC NPs) anchored on carbon nanosheets with low loading of Ru (4.11 wt.%), which significantly promotes the oxygen evolution reaction activity with a η10 of 347 mV and a mass activity of 1430 A gRu−1, eight‐fold higher than that of commercial RuO2 (176 A gRu−1). Theoretical calculations demonstrate that the strong catalyst–support interaction between RuO2 and the WC support could optimize the surrounding electronic structure of Ru sites to reduce the reaction barrier. Considering the likewise excellent catalytic ability for hydrogen production, an acidic overall water splitting (OWS) electrolyzer with a good stability constructed by bifunctional RuO2‐WC NPs only requires a cell voltage of 1.66 V to afford 10 mA cm−2. The unique 0D/2D nanoarchitectures rationally combining a WC support with precious metal oxides provides a promising strategy to tradeoff the high catalytic activity and low cost for acidic OWS applications.