Probing competent electrocatalysts for hydrogen evolution reaction (HER) of water splitting is one of the most hopeful approaches to confront the energy and environmental crisis. Herein, we highlight ultrathin N-doped MoC nanosheets (N-MoC NSs) in the role of greatly efficient platinum-free-based electrocatalysts for the HER. The transformation of crystal phase and structure between MoO nanosheets with a thickness of ∼1.1 nm and N-MoC NSs with a thickness of ∼1.0 nm is studied in detail. Structural analyses make clear that the surfaces of the N-MoC NSs are absolutely encompassed by apical Mo atoms, hence affording an ideal catalyst prototype to expose the role of Mo atoms for the duration of HER catalysis. Theoretical calculations demonstrate that the nanosheet structure, N doping, and particular crystalline phase of MoC produce more exposed Mo active sites, including Mo atoms on the C plane and doped N atoms. Through detailed electrochemical investigations, N-MoC NSs possess HER activity with an onset potential of -48.3 mV vs RHE, Tafel slope of 44.5 mV dec, and overpotential of 99 mV vs RHE at the cathodic current density of 10 mA cm with excellent long-term stability. Lastly, the calcination temperature and dicyandiamide amount can obviously affect the phase transformation and surface structure of molybdenum carbide, resulting in an adjustable HER activity. This synthesis mechanism will facilitate the understanding and optimization of Mo-based electrocatalysts in the energy conversion field.

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The removal of highly toxic, ultra-dilute contaminants of concern has been a primary challenge for clean water technologies. Chromium and arsenic are among the most prevalent heavy metal pollutants in urban and agricultural waters, with current separation processes having severe limitations due to lack of molecular selectivity. Here, we report redox-active metallopolymer electrodes for the selective electrochemical removal of chromium and arsenic. An uptake greater than 100 mg Cr/g adsorbent can be achieved electrochemically, with a 99% reversible working capacity, with the bound chromium ions released in the less harmful trivalent form. Furthermore, we study the metallopolymer response during electrochemical modulation by in situ transmission electron microscopy. The underlying mechanisms for molecular selectivity are investigated through electronic structure calculations, indicating a strong charge transfer to the heavy metal oxyanions. Finally, chromium and arsenic are remediated efficiently at concentrations as low as 100 ppb, in the presence of over 200-fold excess competing salts.

We report an atomic-scale characterization of ZrTe_{5} by using scanning tunneling microscopy. We observe a bulk band gap of ∼80  meV with topological edge states at the step edge and, thus, demonstrate that ZrTe_{5} is a two-dimensional topological insulator. We also find that an applied magnetic field induces an energetic splitting of the topological edge states, which can be attributed to a strong link between the topological edge states and bulk topology. The relatively large band gap makes ZrTe_{5} a potential candidate for future fundamental studies and device applications.

Micro bimorph coils driven by a metalinsulator phase transition in VO2 function as powerful torsional muscles. Reversible torsional motion over one million cycles without degradation is demonstrated, with a superior rotational speed up to ca. 200,000 rpm, an amplitude of 500° per mm length, and a power density up to ca. 39 kW kg⁻¹.

The heterostructure interface provides a powerful platform for exploring rich emergent phenomena, such as interfacial superconductivity and nontrivial topological surface states. Here, SrRuO/SrIrO superlattices were epitaxially synthesized. The magnetic and magneto-transport properties of these superlattices were characterized. A broad cusp-type splitting in the zero-field-cooling/field-cooling temperature-dependent magnetization and magnetization relaxation, which follows the modified stretched function model, accompanied by double hysteresis magnetization loops were demonstrated. These physical effects were modulated by the SrIrO layer thickness, which confirms the coexistence of interfacial spin glass and ferromagnetic ordering in the superlattices. In addition, the topological Hall effect was observed at low temperatures, and it is weakened with the increase of the SrIrO layer thickness. These results suggest that a noncoplanar spin texture is generated at the SrRuO/SrIrO interfaces because of the interfacial Dzyaloshinskii-Moriya interaction. This work demonstrates that SrIrO can effectively induce interfacial Dzyaloshinskii-Moriya interactions in superlattices, which would serve as a mechanism to develop spintronic devices with perovskite oxides.

Catalytic base-free oxidation of biomass-derived glycerol represents a promising approach for the value-added utilization of glycerol. However, the commonly used Pt/carbon nanotubes (Pt/CNT) catalysts suffer from the severe deactivation, because of the strong adsorption of glyceric acid (GLYA), resulting in the serious Pt-surface poisoning and their consequent poor activity with low selectivity toward GLYA. Here, we demonstrate that integrating CeO2 with Pt/CNT could effectively alleviate the catalyst deactivation, delivering high activity and selectivity to produce GLYA. The valence band analysis and kinetic experiments suggest that the Pt-CeO2/CNT ternary interface would weaken the GLYA adsorption on Pt and lower the energy barrier for glycerol oxidation. Moreover, via the generated OH* from H2O dissociation, CeO2 can promote the oxidation of primary hydroxyl groups of glycerol, leading to a high selectivity of GLYA.

The thickness-dependent metal-insulator transition is observed in meta-stable orthorhombic SrIrO3 thin films synthesized by pulsed laser deposition. SrIrO3 films with thicknesses less than 3 nm demonstrate insulating behaviour, whereas those thicker than 4 nm exhibit metallic conductivity at high temperature, and insulating-like behaviour at low temperature. Weak/Anderson localization is mainly responsible for the observed thickness-dependent metal-insulator transition in SrIrO3 films. Temperature-dependent resistance fitting shows that electrical-conductivity carriers are mainly scattered by the electron-boson interaction rather than the electron-electron interaction. Analysis of the magneto-conductance proves that the spin-orbit interaction plays a crucial role in the magneto-conductance property of SrIrO3.