Aqueous zinc-ion batteries are receiving considerable attention, owing to their intrinsic safety and high theoretical capacity; however, they still suffer from a limited lifespan, caused by severe side reactions and...

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Characteristics like air-stability and high carrier mobility make non-van-der-Waals layered Bi2O2Se a good prospect for planar integrated nanosystems. However, experimental investigation about its analogue Bi2O2Te is rather rare due to difficulty in synthesis. Herein, a low-pressure CVD process is proposed that is adjusted to the rigorous growth condition required, with large-scale Bi2O2Te ultrathin film obtained. Magneto-transport behavior reveals a very large anisotropic nonsaturating low-temperature magnetoresistance (∼1133% under 9 T magnetic field). Despite the contradiction between high conductivity and ferroelectricity in principle (mobile electrons screen electrostatic forces between ions), the high-conductive Bi2O2Te film here is revealed experimentally as another intrinsic ferroelectric with the polarization switchable by external electric field (predicted in Nano Lett. 2017, 17, 6309). These results prove that Bi2O2Te possesses a very narrow bandgap (∼0.15 eV), high conductivity, large magnetoresistance, and room-temperature ferroelectricity, displaying great potential as a high-performance nanoelectronic two-dimensional semiconductor and, in advanced functional devices, working in the mid-infrared region.

Following logic in the silicon semiconductor industry, the existence of native oxide and suitable fabrication technology is essential for 2D semiconductors in planar integronics, which are surface-sensitive to typical coating technologies. To date, very few types of integronics are found to possess this feature. Herein, the 2D Bi 2 O 2 Te developed recently is reported to possess large-area synthesis and controllable thermal oxidation behavior toward single-crystal native oxides. This shows that surface-adsorbed oxygen atoms are inclined to penetrate across [Bi 2 O 2 ] n 2n+ layers and bond with the underlying [Te] n 2n− at elevated temperatures, transforming directly into [TeO 4 ] n 2n− with the basic architecture remaining stable. The oxide can be adjusted to form in an accurate layer-by-layer manner with a low-stress sharp interface. The native oxide Bi 2 TeO 6 layer (bandgap of ≈2.9 eV) exhibits visible-light transparency and is compatible with wet-chemical selective etching technology. These advances demonstrate the potential of Bi 2 O 2 Te in planar-integrated functional nanoelectronics such as tunnel junction devices, field-effect transistors, and memristors.

As metal-free carbon based catalysts, boron (B)doped carbonaceous materials have proved to exhibit superior catalytic performance toward nitrogen reduction reaction. However, this strategy of heteroatom doping encounters the synthesis challenges of precise control of the doping level and homogeneous distribution of the dopants, and in particular, these materials cannot be utilized in electrochemical N 2 reduction because of poor electrical conductivity. Accordingly, via first-principles calculations, we here predicted two stable two-dimensional crystalline compounds: BC 6 N 2 and BC 4 N, which have small band gaps and uniform distribution of NRR active sp 2 -B species and holey structures. Between them, the BC 6 N 2 monolayer originally possesses nice NRR activity with limiting potentials of −0.47 V. In the proton-rich acid medium, the electronic properties of these two B−C−N monolayers could be further tailored to exhibit a metallic characteristic by H pre-adsorption. This drastically improves the conductivity and enhances their NRR performances as reflected by the limiting potentials of −0.15, −0.34, and −0.34 V for BC 6 N 2 via enzymatic, distal, and alternating mechanisms, respectively. Besides, NRR on BC 4 N through enzymatic mechanism proceeds as the limiting potential moderated from −1.20 to −0.90 V. More than that, the competing hydrogen evolution reaction can be effectively suppressed. The current investigation opens an avenue of designing a 2D crystalline phase of MFC catalysts independent of heteroatom doping and gives insightful views of surface functionalization as an impactful strategy to improve the electrocatalytic activity of metal-free catalysts.