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Iridium oxide (IrO

2D ultrathin capping agent-free Ir-based nanosheets have been fabricated via a facile strategy by thermally treating ZnIr(OH)6 perovskite hydroxide, which can serve as promising electrocatalysts for overall water splitting.

Over the past decades, despite the substantial efforts that have been devoted to the modifications of Pt nanoparticles (NPs) to tailor their selectivities for hydrogenation reactions, there are still a lack of facile strategies for precisely regulation of the surface properties of NPs, especially for those with small sizes. In this work, we propose a top-down thermal annealing strategy for tuning the surface properties of Pt-based NPs (≈4 nm) without the occurrence of aggregation. Compared to conventional bottom-up methods, the present top-down strategy can precisely regulate the surface compositions of Pt-Cd NPs and other ternary Pt-Cd-M NPs (M=Fe, Ni, Co, Mn, and Sn). The optimized Pt-Cd NPs exhibit excellent selectivity toward phenylacetylene and 4-nitrostyrene hydrogenations with a styrene selectivity and 4-aminophenyl styrene selectivity of 95.2 % and 94.5 %, respectively. This work provides a general strategy for the surface reconstructions of Pt-based NPs, and promotes fundamental research on catalyst design for heterogeneous catalysis.

The size modulation of catalyst particles represents a useful dimension to tune catalytic performances by impacting not only their surface areas but also local electronic structures. It, however, has remained inadequately explored and poorly elucidated. Here, we report the interesting size-dependent selectivity of electrochemical CO2 reduction on In2 O3 nanocrystals. 5-nm nanoparticles and 15-nm nanocubes with focused size distribution are prepared via a facile solvothermal reaction in oleylamine by carefully controlling a set of experimental parameters. They serve as the precatalysts, and are reduced to In nanocrystals while largely inherit the original size feature during electrochemical CO2 reduction. Catalyst derived from 15-nm nanocubes exhibits greater formate selectivity (>95 %) at lower overpotential and negligible side reactions compared to bulk-like samples (indium foil and 200-nm cubes) as well as the catalyst derived from smaller 5-nm nanoparticles. This unique size dependence is rationalized as a result of the competition among different reaction pathways by our theoretical computations. Smaller is not always better in the catalyst design.

Iridium oxide (IrO2) is the predominant electrocatalyst for the oxygen evolution reaction (OER) with high stability in both alkaline and harsh acidic media, but its low efficiency and high cost limit its applications. In this work, we have developed a high-throughput computational strategy based on density functional theory (DFT) and employ the machine-learning (ML) techniques to extensively explore the optimal dopants in IrO2 and enhance its OER activity. Thirty-six kinds of metal dopants are considered to substitute for Ir to form binary and ternary metal oxides with different concentrations, and the most stable surface structures are selected from a total of 4,648 structures for OER activity evaluation. By using the neural network language model (NNLM), we are able to associate the atomic environment with the formation energies of crystals and adsorption free energies of OER intermediates, which is efficient for complex compounds and accurately evaluates the structural stability and electrochemical activity. A series of potential candidates have been identified as superior OER catalysts, and some of them are novel with the lowest calculated overpotential. Our strategy could efficiently explore the promising electrocatalysts, especially for evaluating complex multi-metallic compounds.

Two-dimensional transition metal dichalcogenides (TMDs) nanomaterials, such as MoS2 and WSe2, have proved to be promising electrocatalysts for CO2 reduction, in which the reduction product is CO wi...

Superlattices are attracting extensive attention due to their unique properties. Nevertheless, the observations of superlattices are limited to those layered structures with weak interlayered interactions, and the effect of the superlattice in metal-based nanostructures on catalysis is unexplored yet. We here report a facile wet-chemical method for synthesizing two-dimensional Ru multilayered nanosheets (Ru MNSs) with a superlattice. Characterizations reveal that the superlattice is formed by stacking Ru layers with twisted angles from 2° to 30°. Owing to the strong synergy between the adjacent layers, Ru MNSs can serve as an efficient catalyst for the alkaline hydrogen evolution reaction (HER). Theoretical calculations reveal that the superlattice can induce the strain effect, which leads to lattice contraction and weak *H adsorption ability, as a result of improved HER performance. This work sheds new light on the utilization of the superlattice on enhancing catalysis in metal-based materials.

Organic electrode materials hold unique advantages for electrochemical alkali-ion storage but cannot yet fulfill their potential. The key lies in the design of structurally stable candidates that have negligible solution solubility and can withstand thousands of cycles under operation. To this end, we demonstrate here the preparation of dimensionally stable polyimide frameworks from the two-dimensional cross-linking of tetraaminobenzene and dianhydride. The product consists of hierarchically assembled nanosheets with thin thickness and abundant porosity. Its robust molecular frameworks and advantageous nanoscale features render our polymeric material a promising cathode candidate for both sodium-ion and potassium-ion batteries. Most strikingly, an extraordinary cycle life of up to 6000 cycles at 2 A g

The pursuit of selective two-electron oxygen reduction reaction to H

Almost all surfaces sensitive to the ambient environment are covered by water, whereas the impacts of water on surface-dominated colloidal quantum dot (CQD) semiconductor electronics have rarely been explored. Here, strongly hydrogen-bonded water on hydroxylated lead sulfide (PbS) CQD is identified. The water could pilot the thermally induced evolution of surface chemical environment, which significantly influences the nanostructures, carrier dynamics, and trap behaviors in CQD solar cells. The aggravation of surface hydroxylation and water adsorption triggers epitaxial CQD fusion during device fabrication under humid ambient, giving rise to the inter-band traps and deficiency in solar cells. To address this problem, meniscus-guided-coating technique is introduced to achieve dense-packed CQD solids and extrude ambient water, improving device performance and thermal stability. Our works not only elucidate the water involved PbS CQD surface chemistry, but may also achieve a comprehensive understanding of the impact of ambient water on CQD based electronics., Surface of colloidal quantum dot is sensitive to water, and the interaction could potentially alter its chemical environments. Here, Shi et al. investigate how the interaction effects the nanostructures and carrier dynamic in CQDs, and subsequently introduce meniscus-guided coating technique to mitigate CQD fusion triggered by water adsorption.

There is a lack of straightforward methods to prepare high-quality bismuthene nanosheets, or, even more challengingly, to grow their arrays due to the low melting point and high oxophilicity of bismuth. This synthetic obstacle has hindered their potential applications. In this work, it is demonstrated that the galvanic replacement reaction can do the trick. Under well-controlled conditions, large-area vertically aligned bismuthene nanosheet arrays are grown on Cu substrates of various shapes and sizes. The product features small nanosheet thickness of two to three atomic layers, large surface areas, and abundant porosity between nanosheets. Most remarkably, bismuthene nanosheet arrays grown on Cu foam can enable efficient CO

In hydrogen production, the anodic oxygen evolution reaction (OER) limits the energy conversion efficiency and also impacts stability in proton-exchange membrane water electrolyzers. Widely used Ir-based catalysts suffer from insufficient activity, while more active Ru-based catalysts tend to dissolve under OER conditions. This has been associated with the participation of lattice oxygen (lattice oxygen oxidation mechanism (LOM)), which may lead to the collapse of the crystal structure and accelerate the leaching of active Ru species, leading to low operating stability. Here we develop Sr-Ru-Ir ternary oxide electrocatalysts that achieve high OER activity and stability in acidic electrolyte. The catalysts achieve an overpotential of 190 mV at 10 mA cm-2 and the overpotential remains below 225 mV following 1,500 h of operation. X-ray absorption spectroscopy and 18O isotope-labeled online mass spectroscopy studies reveal that the participation of lattice oxygen during OER was suppressed by interactions in the Ru-O-Ir local structure, offering a picture of how stability was improved. The electronic structure of active Ru sites was modulated by Sr and Ir, optimizing the binding energetics of OER oxo-intermediates.

Here, we report a density functional theory (DFT)-based high-throughput screening method to successfully identify a type of alloy nanoclusters as the electrocatalyst for hydrogen evolution reaction (HER). Totally 7924 candidates of Cu-based alloy clusters of Cu55-nMn (M = Co, Ni, Ru, and Rh) are optimized and evaluated to screening for the promising catalysts. By comparing different structural patterns, Cu-based alloy clusters prefer the core–shell structures with the dopant metal in the core and Cu as the shell atoms. Generally speaking, the HER performance of the Cu-based nanoclusters can be significantly improved by doping transition metals, and the active sites are the bridge sites and three-fold sites on the outer-shell Cu atoms. Considering the structural stability and the electrochemical activity, core–shell CuNi alloy clusters are suggested to be the superior electrocatalyst for hydrogen evolution. A descriptor composing of surface charge is proposed to efficiently evaluate the HER activity of the alloy clusters supported by the DFT calculations and machine-learning techniques. Our screening strategy could accelerate the pace of discovery for promising HER electrocatalysts using metal alloy nanoclusters.

Monolayer CrI3 with robust ferromagnetism has been extensively studied. Its Janus structures could further enhance its applications in spintronic devices. Here we investigate the intrinsic defects and their induced magnetic properties in Janus structures. We constructed the point defects in Janus CrX1.5Y1.5 (X, Y = Cl, Br, I; X ≠ Y) monolayer, and studied the structural stability and migration barriers by first-principles calculations. The single vacancy with one halogen atom missing, is the most stable defect in Cr-rich condition, while the Cr vacancy is preferred to form in halogen-rich condition. Our results revealed that the surface defects not only enhance the intrinsic ferromagnetism of the Janus structures, but also increase the Curie temperatures effectively. The intriguing properties induced by the surface defects make the Janus chromium trihalides monolayer promising for multifunctional nanodevices.

There has been growing research interest in hydrogen bonded organic frameworks (HOFs) by virtue of their great structural crystallinity, large surface areas and porosity. Their potential in electrochemical applications, unfortunately, remains elusive because weak hydrogen bonds would dissociate in solution that eventually compromises the structural integrity. Herein, it is demonstrated that this issue may be overcome by designing and introducing multisite hydrogen bonding within HOFs. 2D molecular sheets are prepared using diaminotriazole as the linkers for the first time. In spite of the molecular thickness (≈1 nm), they are chemically stable and mechanically robust, and have diminished solubility in most polar or nonpolar organic solvents. This solution-stable HOF exhibits an excellent electrochemical performance for Na+ ion storage. In particular, it enables an exceptional cycle life of >10 000 cycles at 1 A g-1 , which is far superior to most other organic electrode materials. Theoretical simulations indicate that the activation barrier for the intralayer or interlayer diffusion of Na+ ions within the organic frameworks is small.

There is a lack of straightforward methods to prepare high-quality bismuthene nanosheets, or, even more challengingly, to grow their arrays due to the low melting point and high oxophilicity of bismuth. This synthetic obstacle has hindered their potential applications. In this work, it is demonstrated that the galvanic replacement reaction can do the trick. Under well-controlled conditions, large-area vertically aligned bismuthene nanosheet arrays are grown on Cu substrates of various shapes and sizes. The product features small nanosheet thickness of two to three atomic layers, large surface areas, and abundant porosity between nanosheets. Most remarkably, bismuthene nanosheet arrays grown on Cu foam can enable efficient CO2 reduction to formate with high Faradaic efficiency of >90%, large current density of 50 mA cm-2 , and great stability.