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Mixed-dimensional heterostructures provide additional freedom to construct diverse functional electronic and optoelectronic devices, gaining significant interest. Herein, highly-aligned pseudo-1D tellurium is epitaxially grown on 2D monolayer transition metal dichalcogenides (TMDs), including MoSe2, MoS2, and WS2. A one-pot chemical vapor deposition (CVD) technique eliminates the normally required transfer steps, thereby producing mixed-dimensional heterostructures with an ultraclean interface. The controllable epitaxial growth of Te/TMD heterostructures are verified by Raman, scanning probe microscopy (SPM), and transmission electron microscopy (TEM) observation. The photoluminescence results indicate that the emission from TMDs is quenched in the heterostructure, confirming the efficient transfer of photogenerated carriers from TMDs to Te. Additionally, the mixed-dimensional p-n Te/MoSe2 heterojunction photodetector presents self-driven behavior with high responsivity (328 mA W-1), external quantum efficiency (79%), and specific detectivity (8.2 x 10(9) Jones). The modified facile synthesis strategy and proposed growth mechanism in this study shed light on synthesizing mixed-dimensional heterojunctions. This opens avenues for fabricating functional devices with reduced sizes and high densities, further enabling miniaturization and integration opportunities.

Metal batteries using lithium, sodium, potassium, zinc, etc., as anodes have garnered tremendous attention in rechargeable batteries because of their highly desirable theoretical energy densities. However, large-scale application of these metal batteries is impeded by dendrite growth on the anode surface, which may penetrate the separator, leading to battery failure. Two dimensional (2D) materials featured by excellent mechanical strength and flexibility, tunable electronic properties and controllable assembly are promising materials for the construction of dendrite-free metal batteries. In this review, we summarize recent advancements of 2D materials for their potential use in critical components of dendrite-free batteries used as: (1) a host or artificial solid-electrolyte for metal anodes; (2) a solid electrolyte or modifier for electrolyte; and (3) an enhancement component for separators design. We conclude that 2D materials hold great promise for tackling the problems associated with dendrite formation by functioning as mechanical reinforcement and metal deposition regulators, along with improved safety, performance, and durability of batteries. Finally, this review discusses new perspectives and future directions in the field of 2D materials towards safe, high-energy metal batteries.

Following publication of the original article [1], the authors noticed that a footnote denoting equal contribution was omitted and the affiliations for the corresponding author are given incorrectly. The following footnote should have been included for authors “Hoilun Wong and Yuyin Li contributed equally to this work.” The corresponding author “Zhengtang Luo” is affiliated only in “Department of Chemical and Biological Engineering and William Mong Institute of Nano Science and Technology, Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong”. These correction do not affect any results or conclusions of the publication. The original article has been corrected. © 2023, Korea Nanotechnology Research Society (KoNTRS).

Strong CO adsorption and facile CO dimerization are the key challenges in electrochemical CO2 reduction towards multi-carbon (C2+) products. We recently showed that CoPc immobilized on a single-walled carbon nanotube can selectively reduce CO2 to methanol. This is enabled through molecular strain, which dramatically improves the CO adsorption energy to CoPc, which in turn facilitates methanol formation. We now examine the extended Phthalocyanine (PcEx) dual atom catalyst (DAC), which is intrinsically strained and contains two catalyst centers, making it a candidate for reducing CO to C2+ products. Using Quantum Mechanics (QM), we screened 20 elements embedded in the PcEx, seeking catalysts with weak hydrogen binding, strong CO binding, and facile CO dimerization. We identified Fe, Ru, Co, and Ir as the best performers and subsequently evaluated the entire CO to C2H4 mechanism (9 steps) using each of these elements as catalysts. In terms of limiting potential and overall exergonicity, we identified CoPcEx as the best catalyst, followed by IrPcEx. We then examined the full CO to C2H4 mechanism on the bimetallic IrCoPcEx catalyst using grand canonical QM to obtain the reaction energetics as a function of applied potential. We conclude that the bimetallic IrCoPcEx is most promising for efficiently converting CO to ethylene. © 2023

Dual-atom catalysts (DACs) have recently emerged as promising and high-activity catalysts for the oxygen reduction reaction (ORR), a key process in many electrochemical energy conversion devices. However, the ORR mechanism and kinetics on DACs has not yet been established. To address this problem, we employed grand canonical potential kinetics (GCP-K) with CANDLE solvation. The behavior of the free energy and grand canonical potential for ORR and hydrogen evolution reaction (HER) intermediates (OO*, OOH*, O*, OH*, and H*) and their corresponding transition states at constant charges were calculated and converted to free energy as a function of applied potential to predict current density as a function of applied potential for ORR (through the associative pathway) and the competitive HER on iron-nickel DAC (FeNiN6-DAC). We find a Tafel slope of 281 mV dec−1 for ORR, comparable with the experimental Tafel slope of 169 mV dec−1 at the current density of −1.7 mA cm−2. The change in concentration of ORR reaction intermediates on FeNiN6-DAC as a function of applied potentials indicates that the dominant intermediate is OH* at potentials >0.25 V vs. RHE. The charge transfer and spin density of Fe active sites reaches a maximum during each proton transfer step. The partial density of states of 3d orbitals on the Fe site indicates that the 3dx2-y2 orbital is near the Fermi level, while the position of the 3dz2 orbital and Fermi level reaches a minimum along the first reaction step of. These insights into the fundamental aspects of ORR on DACs provide guidance for the design of efficient catalysts.

The practical application of naturally abundant sodium (Na) metal anodes with high energy densities is hindered by large volume expansion and dendrite formation during battery operation. This work reports the synthesis of tin selenide nanoparticles uniformly grown on highly conductive, porous 3D graphene foam (SnSe@GF) as a stable host for Na metal anodes and the underlying conversion reactions as their energy storage mechanism. The SnSe@GF electrode prepared via hydrogel coating and phase transformation sustains remarkable reversibility after 1500 cycles in asymmetric cells and delivers extraordinary cyclic stability and low overpotentials for 2000 h at 1 mA cm−2 and 1 mAh cm−2 in symmetric cells. The conversion of crystalline SnSe into low-crystallinity Na15Sn4 and Na2Se dual nucleation sites after pre-sodiation is responsible for the outstanding performance according to the in-situ microscopy and density functional theory calculations. The conversion enables the in-situ formation of a unique interface that possesses high Na affinity featured by abundant active sites, contributing to uniform Na nucleation/plating and dendrite suppression, thus give rising to superior stability and electrochemical performance of the SnSe@GF electrode. The rational design of the current 3D architecture can shed new insights into the development of Na hosts for next-generation rechargeable batteries.

With a high specific capacity and low electrochemical potentials, metal anode batteries that use lithium, sodium and zinc metal anodes, have gained great research interest in recent years, as a potential candidate for high-energy-density storage systems. However, the uncontainable dendrite growth during the repeated charging process, deteriorates the battery performance, reduces the battery life and more importantly, raises safety concerns. With their unique properties, two-dimensional (2D) materials, can be used to modify various components in metal batteries, eventually mitigating the dendrite growth, enhancing the cycling stability and rate capability, thus leading to safe and robust metal anodes. In this paper, we review the recent advances of 2D materials and summarize current research progress of using 2D materials in the applications of (i) anode design, (ii) separator engineering, and (iii) electrolyte modifications by guiding metal ion nucleation, increasing ion conductivity, homogenizing the electric field and ion flux, and enhancing the mechanical strength for safe metal anodes. The 2D material modifications provide the ultimate solution for obtaining dendrite-free metal anodes, realizes the high energy storage application, and indicates the importance of 2D materials development. Finally, in-depth understandings of subsequent metal growth are lacking due to research limitations, while more advanced characterizations are welcome for investigating the metal deposition mechanism. The more facile and simplified preparation of 2D materials possess great prospects in high energy density metal anode batteries, and thus fulfils the development of EVs.

As an environmentally friendly biodegradable material, poly(butylene adipate-co-terephthalate) (PBAT) has been commercialized as a shopping bag, but its high gas permeability weaken its practicability in mulch, cling film and other fields. Two kinds of barrier materials, poly(propylene carbonate) (PPC) and organically modified montmorillonite (OMt), are used to prepare PBAT/PPC/OMt composites, and the mechanical properties are improved by chain extender (Joncryl® ADR 4468). The dispersion and arrangement of nanomaterials in blends are studied with different molding methods and their effects on the gas barrier and mechanical properties are studied as well. Dissipative particle dynamics are used to simulate the rate at which O2 molecules pass through the modified PBAT films. The results show that 1 wt% of chain extender can increase the tensile stress and tear strength by about 10% and 15%, respectively. The OMt is preferentially distributed in the PBAT matrix and has a more uniform degree of orientation in the blown film, which is beneficial to the improvement of gas barrier properties. Eventually, the mechanical properties and gas permeability of PBAT films can be regulated through the adjustment of processing methods and the synergistic effect of PPC and OMt, providing a new way for high-performance packaging or agricultural mulching film materials. © 2023

A new reactive force field based on quantum mechanical data for describing formation of the Zn electrode-electrolyte interface (EEI) chemistry in aqueous zinc-ion batteries (ZIBs) is developed. This is the first demonstration in which Reactive Molecular Dynamics (RMD) simulation is used to follow the Zn reduction and anode structural evolution at the EEI. It is found that under axial pressure, Zn dendrite formation is inhibited. This is associated with accelerated ion transport and reduction while increasing preference towards horizontal (002) plane growth. Pressure-induced desolvation of Zn ions within the electric double layer, which promotes faster reduction kinetics is observed. It is found that axial pressure stabilizes adatoms on the (002) plane by decreasing axial atom stress during nucleation and by increasing favorable lateral adatom diffusion, which reduces atomic scale dendrite formation. Finally, these are confirmed results by experimental characterization and electrochemical tests. © 2023 Wiley-VCH GmbH.

Owing to the moderate redox potential and high safety, Zn metal anodes have been garnering great attention. However, the poor reversibility and limited-service period caused by side reactions and dendrites hinder their applications. Here, a novel anode material consisting of a hexagonal 1T-Vanadium diselenide (1T-VSe2) film on graphene is developed as a zincophilic template to epitaxially electrodeposit hexagonal closest packed Zn to replace the conventional metal substrates in Zn batteries. The 1T-VSe2/Zn anode induces a horizontally (002)-oriented plate-like Zn crystal deposition morphology instead of randomly oriented grains that prompts the compact Zn deposition. According to density functional theory calculations, the VSe2 substrate exhibits a higher Zn adsorption (-0.54 eV) than the graphene (-0.38 eV) or neat Zn (-0.48 eV) counterparts, leading to the enhanced zincophilicity and a lower nucleation overpotential, in agreement with the experimental results. The force field-based molecular dynamics simulations visualize Zn nucleation and morphological evolution at the atomistic level. The rapid adatom diffusion on VSe2 leads to layer-by-layer Zn electrodeposits with higher fraction of the (002) facets to effectively prohibit dendrite formation. The symmetric cell with 1T-VSe2/Zn delivers an ultra-stable cyclic life of 2500 h with 50 mV overpotential at 1 mA cm(-2) and 1 mAh cm(-2).

To date, the synthesis of high-quality 2D crystals using vapor deposition methods usually requires high temperature, hindering the integration of 2D materials with Si circuits and exacerbating energy consumption. Exploring low-temperature growth strategies and understanding synthesis mechanism are critical for the practical application of 2D materials. Herein, a van der Waals (vdW) template-assisted growth of 2D crystals (including PbI2, CdI2, BiI3, CuI, Sb2Te3, and Bi2Se3) is reported, the growth temperature decreases by maximum 35% compared with traditional vapor deposition. The low-temperature 2D growth process resulting from the low surface diffusion barrier of precursors on vdW surfaces is proposed, confirmed by the density functional theory and molecular dynamics calculations. Particularly, the grown 2D crystals can be peeled off from vdW templates easily and transferred to arbitrary substrates for functional applications and the exfoliated vdW templates can be reused for another round of growth. Although the growth temperature is reduced greatly, the excellent photoelectric performance of grown 2D crystals is demonstrated, benefitting from high crystalline quality. These findings provide a universal method for the low-temperature synthesis of high-crystallinity 2D materials toward applications in flexible electronics. © 2022 Wiley-VCH GmbH.

Lithium metal battery has high theoretical specific capacity but suffers from dendrite growth that leads to low Columbic Efficiency (CE) and uncontrolled volume expansion during cycling. Here, we develop a method for fabrication of a nitrogen-doped carbon-coating as a lithophilic diffusion barrier layer, by carbonizing polydopamine (PDA) on three-dimensional (3D) porous stainless steel (called Nitrogen-doped carbon stainless steel, N-C-SS) mesh, and used it as the current collector for Li metal anode. With this layer, we observed significant suppression of Li dendrite formation during Li deposition. More specifically, the N-C-SS/Li anode in symmetric cells exhibit stable cycling for over 1800 h, 4 times longer than the bare Li electrode. Similarly, the fabricated half cells retain an average CE of 98.1% after cycling 400 times and show a low overpotential of 12 mV, while for fabricated full cells, they retain 98.6% of their initial capacity 140 mA h g−1 after 200 cycles at 3C. Density functional theory (DFT) calculation results show that N-C-SS surface enables higher diffusion barrier, with more negative Li adsorption energy than the untreated SS surface or Cu or Li substrate, which guides Li nucleation and suppresses dendrite growth on the barrier layer. An additional advantage of SS framework is that the 3D SS mesh skeleton distributes Li along with the mesh uniformly and provides ample voids to accommodate high Li loading (>10 mA h cm−2), while simultaneously minimizes local current density. © 2020