https://tandfonline.com/doi/pdf/10.1080/14686996.2019.1599694

New development of atomic layer deposition: processes, methods and applications.

Energy storage and conversion systems, including batteries, supercapacitors, fuel cells, solar cells, and photoelectrochemical water splitting, have played vital roles in the reduction of fossil fuel usage, addressing environmental issues and the development of electric vehicles. The fabrication and surface/interface engineering of electrode materials with refined structures are indispensable for achieving optimal performances for the different energy-related devices. Atomic layer deposition (ALD) and molecular layer deposition (MLD) techniques, the gas-phase thin film deposition processes with self-limiting and saturated surface reactions, have emerged as powerful techniques for surface and interface engineering in energy-related devices due to their exceptional capability of precise thickness control, excellent uniformity and conformity, tunable composition and relatively low deposition temperature. In the past few decades, ALD and MLD have been intensively studied for energy storage and conversion applications with remarkable progress. In this review, we give a comprehensive summary of the development and achievements of ALD and MLD and their applications for energy storage and conversion, including batteries, supercapacitors, fuel cells, solar cells, and photoelectrochemical water splitting. Moreover, the fundamental understanding of the mechanisms involved in different devices will be deeply reviewed. Furthermore, the large-scale potential of ALD and MLD techniques is discussed and predicted. Finally, we will provide insightful perspectives on future directions for new material design by ALD and MLD and untapped opportunities in energy storage and conversion.

Atomic/molecular layer deposition for energy storage and conversion.

Aluminum hydride (AlH3) is one of the most promising hydrogen storage materials that has a high theoretical hydrogen storage capacity (10.08 wt%) and relatively low dehydriding temperature (100–200 °C). In this work, we present a cost-effective route to synthesize the α-AlH3 nano-composite by using cheap metal hydrides and aluminum chloride as starting reagents and to achieve liquid state reactive milling. The LiH/AlCl3 and MgH2/AlCl3 reaction systems were systemically explored. The phase identification of the obtained products was carried out by XRD and the morphology observed by TEM characterization. It was found that the α-AlH3 nano-composite can be successfully synthesized by reactive milling of commercial AlCl3 and LiH in a neutral ionic liquid ([2-Eim] OAc). Based on XRD analysis and TEM observation, an average grain size of 56 nm can be obtained by the proposed mechanochemical process. By setting the isothermal dehydrogenation temperature between 80 and 160 °C, the as-synthesized α-AlH3 nano-composite exhibits an advantage in hydrogen desorption capacity and has fast dehydriding kinetics. The hydrogen desorption content of 9.93 wt% was achieved at 160 °C, which indicates the potential utilization of the prepared nanocomposite in hydrogen storage applications.

Ionic liquids as an efficient medium for the mechanochemical synthesis of α-AlH3 nano-composites

All-inorganic perovskite quantum dots suffer from poor stability in a humid and heat environment. In this article, CsPbBr3 quantum dots (CsPbBr3 QDs) are stabilized by coating nanoscale alumina on a CsPbBr3 QDs-silica luminescent sphere (CsPbBr3 QDs-SLS) via atomic layer deposition (ALD). Utilizing the intrinsic reactivity differences toward precursors, the surface defect sites of CsPbBr3 QDs are selectively passivated. The inorganic alumina coating layers can effectively reduce the ion migration and crystal deformation of CsPbBr3 QDs. In situ quartz crystal microbalance measurements show that organic ligands remain attached to the CsPbBr3 QDs surface during the ALD coating process. NMR, XPS, and first-principles calculations are performed to reveal the interaction strength between CsPbBr3 QDs-SLS and precursors. The surface passivation of alumina on CsPbBr3 QDs-SLS effectively stabilizes the QDs without reducing the photoluminescent quantum yield.

Bottom up Stabilization of CsPbBr3 Quantum Dots-Silica Sphere with Selective Surface Passivation via Atomic Layer Deposition

Graphene-based nanomaterials are promising bifunctional electrocatalysts for overall water splitting (OWS) to produce hydrogen and oxygen as sustainable fuel sources because graphene-based bifunctional electrocatalysts can provide distinct features such as large surface areas, more active sites and facile synthesis of multiple co-doped nanomaterials. Based on this, this review will present recent advancements in the development of various bifunctional graphene-based electrocatalysts for OWS reactions and discuss advancements in the tuning of electronic surface-active sites for the electrolytic splitting of water. In addition, this review will evaluate perspectives and challenges to provide a deep understanding of this emerging field.

Recent Progress in Graphene-Based Nanostructured Electrocatalysts for Overall Water Splitting

A fluidized bed coupled rotary reactor has been designed for coating on nanoparticles (NPs) via atomic layer deposition. It consists of five major parts: reaction chamber, dosing and fluidizing section, pumping section, rotary manipulator components, as well as a double-layer cartridge for the storage of particles. In the deposition procedure, continuous fluidization of particles enlarges and homogenizes the void fraction in the particle bed, while rotation enhances the gas-solid interactions to stabilize fluidization. The particle cartridge presented here enables both the fluidization and rotation acting on the particle bed, demonstrated by the analysis of pressure drop. Moreover, enlarged interstitials and intense gas–solid contact under sufficient fluidizing velocity and proper rotation speed facilitate the precursor delivery throughout the particle bed and consequently provide a fast coating process. The cartridge can ensure precursors flowing through the particle bed exclusively to achieve high utilization without static exposure operation. By optimizing superficial gas velocities and rotation speeds, minimum pulse time for complete coating has been shortened in experiment, and in situ mass spectrometry showed the precursor usage can reach 90%. Inductively coupled plasma-optical emission spectroscopy results suggested a saturated growth of nanoscale Al2O3 films on spherical SiO2 NPs. Finally, the uniformity and composition of the shells were characterized by high angle annular dark field-transmission electron microscopy and energy dispersive X-ray spectroscopy.

Fluidized bed coupled rotary reactor for nanoparticles coating via atomic layer deposition.

Aluminum hydride (AlH3), with gravimetric hydrogen capacity exceeding 10 wt. %, has shown a great potential as an alternative energy storage material. Due to its high reactivity, the practical utilization of AlH3 relies on its safe storage, handling, and transportation. During its storage, hydrogen would be slowly released through the reaction with moisture and oxygen under ambient conditions. When mixed with other fuels during transportation, the heat generated from interparticle friction may lead to a temperature rise, resulting in rapid hydrogen release and may even trigger explosion. Thus, it is imperative to passivate the AlH3 particles to prevent its reactions with moisture and oxygen and insulate them from friction heat. In this paper, microscale α-AlH3 particles were passivated by nanometer Al2O3 layers via atomic layer deposition. Conformal amorphous Al2O3 films were coated around the crystalline α-AlH3 particles, serving as physical barriers to prevent reactions. Through hydrothermal aging tests, the retained hydrogen capacity of passivated particles was four times higher than the untreated sample. At the same time, alumina films prevented the transfer of friction heat to inner cores, reducing the potential risks associated with handling or transportation. The overall hydrogen capacity reduction was as less as 5%, primarily due to the mass gain of Al2O3 encapsulation layers. The dehydrogenation speed of passivated AlH3 particles was about the same as that of untreated samples, indicating that this is a feasible technique to stabilize AlH3 without sacrificing its energy release capacity.

Surface passivation of aluminum hydride particles via atomic layer deposition

Iron(II,III) oxide (Fe3O4) nanoparticles have shown great promise in many magnetic-related applications such as magnetic resonance imaging, hyperthermia treatment, and targeted drug delivery. Nevertheless, these nanoparticles are vulnerable to oxidation and magnetization loss under ambient conditions, and passivation is usually required for practical applications. In this work, a home-built rotating fluidized bed (RFB) atomic layer deposition (ALD) reactor was employed to form dense and uniform nanoscale Al2O3 passivation layers on Fe3O4 nanoparticles. The RFB reactor facilitated the precursor diffusion in the particle bed and intensified the dynamic dismantling of soft agglomerates, exposing every surface reactive site to precursor gases. With the aid of in situ mass spectroscopy, it was found that a thicker fluidization bed formed by larger amount of particles increased the residence time of precursors. The prolonged residence time allowed more thorough interactions between the particle surfaces and the...

Surface passivation of Fe3O4 nanoparticles with Al2O3 via atomic layer deposition in a rotating fluidized bed reactor

The stability of aluminum (Al) nanoparticles is a key issue that determines the energy performance of solid fuels, Al-based green propellants, and fuel cells. The surface native oxide shell (Al2O3)...

Ultrathin Zirconia Passivation and Stabilization of Aluminum Nanoparticles for Energetic Nanomaterials via Atomic Layer Deposition

Spatial atomic layer deposition (SALD) is a promising technology with the aim of combining the advantages of excellent uniformity and conformity of temporal atomic layer deposition (ALD), and an industrial scalable and continuous process. In this manuscript, an experimental and numerical combined model of atmospheric SALD system is presented. To establish the connection between the process parameters and the growth efficiency, a quantitative model on reactant isolation, throughput, and precursor utilization is performed based on the separation gas flow rate, carrier gas flow rate, and precursor mass fraction. The simulation results based on this model show an inverse relation between the precursor usage and the carrier gas flow rate. With the constant carrier gas flow, the relationship of precursor usage and precursor mass fraction follows monotonic function. The precursor concentration, regardless of gas velocity, is the determinant factor of the minimal residual time. The narrow gap between precursor injecting heads and the substrate surface in general SALD system leads to a low Peclet number. In this situation, the gas diffusion act as a leading role in the precursor transport in the small gap rather than the convection. Fluid kinetics from the numerical model is independent of the specific structure, which is instructive for the SALD geometry design as well as its process optimization.

Duan Chenlong

Papers

Fluidized bed coupled rotary reactor for nanoparticles coating via atomic layer deposition.

Surface passivation of aluminum hydride particles via atomic layer deposition

Surface passivation of Fe3O4 nanoparticles with Al2O3 via atomic layer deposition in a rotating fluidized bed reactor

Ultrathin Zirconia Passivation and Stabilization of Aluminum Nanoparticles for Energetic Nanomaterials via Atomic Layer Deposition

Mechanistic modeling study on process optimization and precursor utilization with atmospheric spatial atomic layer deposition