Engineering grain boundaries at the 2D limit for the hydrogen evolution reaction

Atom-thin transition metal dichalcogenides (TMDs) have emerged as fascinating materials and key structures for electrocatalysis. So far, their edges, dopant heteroatoms and defects have been intensively explored as active sites for the hydrogen evolution reaction (HER) to split water. However, grain boundaries (GBs), a key type of defects in TMDs, have been overlooked due to their low density and large structural variations. Here, we demonstrate the synthesis of wafer-size atom-thin TMD films with an ultra-high-density of GBs, up to ~1012 cm−2. We propose a climb and drive 0D/2D interaction to explain the underlying growth mechanism. The electrocatalytic activity of the nanograin film is comprehensively examined by micro-electrochemical measurements, showing an excellent hydrogen-evolution performance (onset potential: −25 mV and Tafel slope: 54 mV dec−1), thus indicating an intrinsically high activation of the TMD GBs

Phosphate Removal by Ca-Modified Magnetic Sludge Biochar Prepared by a One-Step Hydrothermal Method

The problem of phosphorus pollution and its resource utilization has been a source of general concern. The preparation of green, renewable, and non-secondary pollution adsorbents has become a research direction. In this paper, a one-step hydrothermal preparation method of Ca-modified magnetic sludge biochar (Ca-MSBC) is used for enhancing phosphate removal. The results show that the adsorption rate of phosphate by Ca-MSBC is mainly controlled by chemisorption but is also related to physical adsorption and an internal diffusion mechanism. The maximum phosphorus adsorption capacity of Ca-MSBC was 89.25 mg g−1 at 343 K (initial phosphate concentration 500 mg L−1). After nine cycles of adsorption experiments, the adsorption capacity of 70.16 mg g−1 was still high. In addition, coexisting ions Cl−, NO3−, SO42−, and CO32− have no significant effect on the adsorption properties of phosphate. XRD, FT-IR, VSM, XPS, and N2 adsorption/desorption isotherms showed that the mechanism of phosphate removal from water by Ca-MSBC was mainly the chemical precipitation reaction of phosphate and calcium. The results of this study indicate that Ca-MSBC has potential application and environmental value as a solid waste recycling material for environmental remediation

Electrically tunable two-dimensional heterojunctions for miniaturized near-infrared spectrometers.

Miniaturized spectrometers are of considerable interest for their portability. Most designs to date employ a photodetector array with distinct spectral responses or require elaborated integration of micro & nano optic modules, typically with a centimeter-scale footprint. Here, we report a design of a micron-sized near-infrared ultra-miniaturized spectrometer based on two-dimensional van der Waals heterostructure (2D-vdWH). By introducing heavy metal atoms with delocalized electronic orbitals between 2D-vdWHs, we greatly enhance the interlayer coupling and realize electrically tunable infrared photoresponse (1.15 to 1.47 μm). Combining the gate-tunable photoresponse and regression algorithm, we achieve spectral reconstruction and spectral imaging in a device with an active footprint < 10 μm. Considering the ultra-small footprint and simple fabrication process, the 2D-vdWHs with designable bandgap energy and enhanced photoresponse offer an attractive solution for on-chip infrared spectroscopy

Direct growth of single-metal-atom chains

Single-metal-atom chains (SMACs), as the smallest one-dimensional structure, have intriguing physical and chemical properties. Although several SMACs have been realized so far, their controllable fabrication remains challenging due to the need to arrange single atoms in an atomically precise manner. Here we develop a chemical vapour co-deposition method to construct a wafer-scale network of platinum SMACs in atom-thin films. The obtained atomic chains possess an average length of up to ~17 nm and a high density of over 10 wt%. Interestingly, as a consequence of the electronic delocalization of platinum atoms along the chain, this atomically coherent one-dimensional channel delivers a metallic behaviour, as revealed by electronic measurements, first-principles calculations and complex network modelling. Our strategy is potentially extendable to other transition metals such as cobalt, enriching the toolbox for manufacturing SMACs and paving the way for the fundamental study of one-dimensional systems and the development of devices comprising monoatomic chains