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Experiments have shown that graphene-supported Ni-single atom catalysts (Ni-SACs) provide a promising strategy for the electrochemical reduction of CO 2 to CO, but the nature of the Ni sites (Ni-N 2 C 2 , Ni-N 3 C 1 , Ni-N 4 ) in Ni-SACs has not been determined experimentally. Here, we apply the recently developed grand canonical potential kinetics (GCP-K) formulation of quantum mechanics to predict the kinetics as a function of applied potential (U) to determine faradic efficiency, turn over frequency, and Tafel slope for CO and H 2 production for all three sites. We predict an onset potential (at 10 mA cm −2 ) U onset  = −0.84 V (vs. RHE) for Ni-N 2 C 2 site and U onset  = −0.92 V for Ni-N 3 C 1 site in agreement with experiments, and U onset  = −1.03 V for Ni-N 4 . We predict that the highest current is for Ni-N 4 , leading to 700 mA cm −2 at U = −1.12 V. To help determine the actual sites in the experiments, we predict the XPS binding energy shift and CO vibrational frequency for each site. Single atom catalysts (SACs) are promising in electrocatalysis but challenging to characterize. Here, the authors apply a recently developed quantum mechanical grand canonical potential kinetics method to predict reaction mechanisms and rates for CO 2 reduction at different sites of graphene-supported Ni-SACs.

Electrocatalytic nanocarbon (EN) is a class of material receiving intense interest as a potential replacement for expensive, metal-based electrocatalysts for energy conversion and chemical production applications. The further development of EN will require an intricate knowledge of its catalytic behaviors, however, the true nature of their electrocatalytic activity remains elusive. This review highlights work that contributed valuable knowledge in the elucidation of EN catalytic mechanisms. Experimental evidence from spectroscopic studies and well-defined molecular models, along with the survey of computational studies, is summarized to document our current mechanistic understanding of EN-catalyzed oxygen, carbon dioxide and nitrogen electrochemistry. We hope this review will inspire future development of synthetic methods and in situ spectroscopic tools to make and study well-defined EN structures. Electrocatalytic nanocarbon (EN) is a class of materials receiving intense interest as next generation electrocatalysts. Although impressive platforms, work is still required to develop our mechanistic understanding of them to that of molecular electrocatalysts.

Two-dimensional (2D) transition metal dichalcogenides (TMDs) have stimulated the modern technology due to their unique and tunable electronic, optical, and chemical properties. Therefore, it is very important to study the control parameters for material preparation to achieve high quality thin films for modern electronics, as the performance of TMDs-based device largely depends on their layer number, grain size, orientation, and morphology. Among the synthesis methods, chemical vapor deposition (CVD) is an excellent technique, vastly used to grow controlled layer of 2D materials in recent years. In this review, we discuss the different growth routes and mechanisms to synthesize high quality large size TMDs using CVD method. We highlight the recent advances in the controlled growth of mono- and few-layer TMDs materials by varying different growth parameters. Finally, different strategies to control the grain size, boundaries, orientation, morphology and their application for various field of are also thoroughly discussed.

The integration of various two-dimensional (2D) materials on wafers enables a more-than-Moore approach for enriching the functionalities of devices 1 – 3 . On the other hand, the additive growth of 2D materials to form heterostructures allows construction of materials with unconventional properties. Both may be achieved by materials transfer, but often suffer from mechanical damage or chemical contamination during the transfer. The direct growth of high-quality 2D materials generally requires high temperatures, hampering the additive growth or monolithic incorporation of different 2D materials. Here we report a general approach of growing crystalline 2D layers and their heterostructures at a temperature below 400 °C. Metal iodide (MI, where M = In, Cd, Cu, Co, Fe, Pb, Sn and Bi) layers are epitaxially grown on mica, MoS 2 or WS 2 at a low temperature, and the subsequent low-barrier-energy substitution of iodine with chalcogens enables the conversion to at least 17 different 2D crystalline metal chalcogenides. As an example, the 2D In 2 S 3 grown on MoS 2 at 280 °C exhibits high photoresponsivity comparable with that of the materials grown by conventional high-temperature vapour deposition (~700–1,000 °C). Multiple 2D materials have also been sequentially grown on the same wafer, showing a promising solution for the monolithic integration of different high-quality 2D materials. High-quality crystalline two-dimensional layers of metal halides can be on mica, MoS 2 or WS 2 at temperatures below 400 °C.

The properties of van der Waals (vdW) materials often vary dramatically with the atomic stacking order between layers, but this order can be difficult to control. Trilayer graphene (TLG) stacks in either a semimetallic ABA or a semiconducting ABC configuration with a gate-tunable band gap, but the latter has only been produced by exfoliation. Here we present a chemical vapor deposition approach to TLG growth that yields greatly enhanced fraction and size of ABC domains. The key insight is that substrate curvature can stabilize ABC domains. Controllable ABC yields ~59% were achieved by tailoring substrate curvature levels. ABC fractions remained high after transfer to device substrates, as confirmed by transport measurements revealing the expected tunable ABC band gap. Substrate topography engineering provides a path to large-scale synthesis of epitaxial ABC-TLG and other vdW materials. The semiconducting ABC configuration of trilayer graphene is more challenging to grow on large scales than its semimetallic ABA counterpart. Here, an approach to trilayer growth via chemical vapor deposition is presented that utilizes substrate curvature to yield enhanced fraction and size of ABC domains.

The design of high‐entropy single‐atom catalysts (HESAC) with 5.2 times higher entropy compared to single‐atom catalysts (SAC) is proposed, by using four different metals (FeCoNiRu‐HESAC) for oxygen reduction reaction (ORR). Fe active sites with intermetallic distances of 6.1 Å exhibit a low ORR overpotential of 0.44 V, which originates from weakening the adsorption of OH intermediates. Based on density functional theory (DFT) findings, the FeCoNiRu‐HESAC with a nitrogen‐doped sample were synthesized. The atomic structures are confirmed with X‐ray photoelectron spectroscopy (XPS), X‐ray absorption (XAS), and scanning transmission electron microscopy (STEM). The predicted high catalytic activity is experimentally verified, finding that FeCoNiRu‐HESAC has overpotentials of 0.41 and 0.37 V with Tafel slopes of 101 and 210 mVdec−1 at the current density of 1 mA cm−2 and the kinetic current densities of 8.2 and 5.3 mA cm−2, respectively, in acidic and alkaline electrolytes. These results are comparable with Pt/C. The FeCoNiRu‐HESAC is used for Zinc–air battery applications with an open circuit potential of 1.39 V and power density of 0.16 W cm−2. Therefore, a strategy guided by DFT is provided for the rational design of HESAC which can be replaced with high‐cost Pt catalysts toward ORR and beyond. This study introduces high‐entropy single‐atom catalysts (HESAC) incorporating four metals in FeCoNiRu‐HESAC. The catalyst is predicted to have an ORR overpotential of 0.44 V, which is verified experimentally to be 0.41 V (acidic electrolyte) and 0.37 V (alkaline electrolyte). A Zinc–air battery based on this catalyst achieves an open circuit potential of 1.39 V and a power density of 0.16 W cm−2.

Tissue engineering has provided an alternative strategy for the regeneration of functional tissues for drug screening and disease intervention. The central challenge in the development of mature and functional excitable tissues is to design and construct advanced conductive biomaterials that can guide cells to form electrically interconnected networks. The objective of this study was to develop reduced graphene oxide modified silk nanofibrous biomaterials with controllable surface deposition on the nanoscale. A vacuum filtration system was applied to attain reduced graphene oxide nanolayer deposition. The results demonstrate that with this method, a uniform and compact reduced graphene oxide nanolayer was formed, and the conductivity and nanofibrous morphology of the materials was well controlled. The composite nanofibrous scaffolds were applied for the engineering of cardiac tissues and demonstrated a great ability to promote tissue formation and functions, including the expression of cardiac-specific proteins, the formation of sarcomeric structures and gap junctions, and tissue contraction. External electrical stimulation further enhanced the maturation level of cardiac tissues cultured on these conductive scaffolds. All these results demonstrated the great potential of reduced graphene oxide functionalized silk biomaterials fabricated using our method for recapitulating electrical microenvironments for the regeneration of functional excitable tissues.

Significant changes in the Raman spectrum of single-layer graphene grown on a copper film were observed after the spontaneous oxidation of the underlying substrate that occurred under ambient conditions. The frequencies of the graphene G and 2D Raman modes were found to undergo red shifts, while the intensities of the two bands change by more than an order of magnitude. To understand the origin of these effects, we further characterized the samples by scanning tunneling microscopy （STM）, scanning tunneling spectroscopy （STS）, and atomic force microscopy （AFM）. The oxidation of the substrate produced an appreciable corrugation in the substrate without disrupting the crystalline order of the graphene overlayer and/or changing the carrier doping level. We explain the red shifts of the Raman frequencies in terms of tensile strain induced by corrugation of the graphene layer. The changes in Raman intensity with oxidation arise from the influence of the thin cuprous oxide film on the efficiency of light coupling with the graphene layer in the Raman scattering process.

Dopamine is a key neurotransmitter that plays essential roles in the central nervous system, including motor control, motivation, arousal, and reward. Thus, abnormal levels of dopamine directly cause several neurological diseases, including depressive disorders, addiction, and Parkinson’s disease (PD). To develop a new technology to treat such diseases and disorders, especially PD, which is currently incurable, dopamine release from living cells intended for transplantation or drug screening must be precisely monitored and assessed. Owing to the advantages of miniaturisation and rapid detection, numerous electrical techniques have been reported, mostly in combination with various nanomaterials possessing specific nanoscale geometries. This review highlights recent advances in electrical biosensors for dopamine detection, with a particular focus on the use of various nanomaterials (e.g., carbon-based materials, hybrid gold nanostructures, metal oxides, and conductive polymers) on electrode surfaces to improve both sensor performance and biocompatibility. We conclude that this review will accelerate the development of electrical biosensors intended for the precise detection of metabolite release from living cells, which will ultimately lead to advances in therapeutic materials and techniques to cure various neurodegenerative disorders.

CH3NH3PbI3-xClx species were fabricated as light-absorbing layers for perovskite solar cells (PSCs), by employing NH4I, NH4Br, and NH4Cl as additives via annealing at 100 °C for different times. Solutions containing CH3NH3I, PbI2, and PbCl2 (4:1:1 molar ratio) in N,N-dimethylformamide were used to prepare perovskites with NH4I, NH4Br, and NH4Cl as additives, at concentrations of 0.1 M and 0.3 M. The additives helped increase the grain size and reduce pinholes in the perovskite films, as confirmed by field-emission scanning electron microscopy. The X-ray diffraction profiles of CH3NH3PbI3-xClx clearly showed peaks at 14° and 28° for the samples with additives, indicative of crystallinity. The best PSC performance with a power conversion efficiency of 9.13%, was achieved using 0.1 M NH4I by annealing for 5 min, whereas the power conversion efficiency of the perovskite solar cells without additives was 5.40%.