Influence of dipping cycle on SILAR synthesized NiO thin film for improved electrochemical performance

In situ optimization of deposition layers in Ni-Co phosphate electrodes with ML-assisted predictive validation for superior supercapacitor

The successive ionic layer adsorption and reaction (SILAR) methodology provides an economically viable and uncomplicated strategy for the fabrication of electrode materials intended for applications in energy storage. The present work focuses on synthesizing Ni-Co phosphate nanoparticles on nickel foam (NF) through the controlled deposition of multiple layers using the SILAR method. The amorphous phase of the Ni-Co phosphate on the electrodes was confirmed via XRD analysis. In contrast, the existence of the phosphate group was confirmed through FT-IR and EDS analysis. The XPS analysis shows that nickel and cobalt exist in varying oxidation states of Ni2+/Ni3+ and Co2+/Co3+, facilitating a reversible charge storage process, while phosphorus is present in its pentavalent state. The electrode demonstrated exceptional performance at a current density of 1 mA cm-2, achieving a high areal capacitance of 426.47 mF cm-2 (equivalent to 2132 F g-1). Additionally, it exhibited remarkable rate capability at 5 mA cm-2, retaining 76.4% of the capacitance observed at 1 mA cm-2. Moreover, the material exhibited remarkable cyclic stability following 5000 cycles of charge-discharge at 5 mA cm-2, maintaining 77.92% of its original capacitance in a three-electrode setup. Additionally, the trained ML model showed high predictive accuracy. The predicted capacitance of 2129 F g-1 closely matched the experimental value of 2132 F g-1, demonstrating the model's reliability. These findings underscore the potential of SILAR-grown Ni-Co phosphate for supercapacitor applications, further enhanced by integrating ML for performance prediction.

Facile and cost-effective NiO/MgO-SiO2 composites for efficient oxygen evolution reaction and asymmetric supercapacitor systems

Biomass waste from grapefruit peel extract was used for the preparation of MgO-SiO2 composites in situ in order to develop effective electrocatalytic composites based on NiO/MgO-SiO2. The MgO-SiO2 composites were subsequently deposited with NiO using a modified hydrothermal method. The synthesized materials were analyzed to investigate their morphology, crystal structure, chemical composition, functional group, and optical band gap. The structural analysis allowed us to determine the orientation of the nanoparticles, the cubic phase of NiO and MgO, the significant loss of optical band gap, and the enriched functional groups on the surface of NiO/MgO-SiO2 composites. The electrochemical properties were investigated in the presence of an alkaline solution of KOH. To study the oxygen evolution reaction (OER) in 1 M KOH aqueous solution, different NiO/MgO-SiO2 composites were investigated. It was found that the NiO/MgO-SiO2 composite that contained the highest amount of MgO-SiO2 (sample 3) had a lower overpotential than the NiO/MgO-SiO2 composite with the lowest amount of MgO-SiO2. Sample 3 exhibited an overpotential of 230 mV at 10 mA cm-2 over a period of 40 hours with excellent stability. The superior electrochemical activity of the NiO/MgO-SiO2 composite (sample 3) was demonstrated in an energy storage device using 3 M KOH aqueous solution, and asymmetric supercapacitor devices were fabricated in 3 M KOH solution. According to the ASC's specifications, a specific capacitance of 344.12 F g-1 and an energy density of 7.31 W h kg-1 were found for the device at a fixed current density of 1.5 A g-1. After over 40 000 galvanic charge-discharge repeatable cycles at 1.5 A g-1, sample 3 of the NiO/MgO-SiO2 composite exhibited excellent cycling stability with 88.9% percent capacitance retention. During the performance evaluation of the NiO/MgO-SiO2 composites, grapefruit peel extract was confirmed as a potential biomass waste for the fabrication of high-performance energy conversion and storage devices.

Automated Instrument for the Deposition of Thin Films Using Successive Ionic Layer Adsorption and Reaction

The development and improvement of thin film deposition techniques is an important research topic to obtain new materials at submicro and nano scale with high homogeneity and thickness control. Here, we designed and built an automated device for the deposition of binary or ternary compound films using Successive Ionic Layer Adsorption and Reaction (SILAR). The instrument is integrated by three different systems. The first system consists of a mobile platform of two degrees of freedom. The second part has an 8-bit microcontroller used to adjust the velocities along the horizontal and vertical axes. The third, the control system, uses a mobile app that can be implemented in smart devices, developed in free code software for programming and monitoring the main deposition parameters of the SILAR device such as the number of cycles, the immersion and emersion velocities, the residence time at each step, and the number of reactors. The performance of our instrument was verified through the deposition of PbS films, varying the number of deposition cycles to study the variations in the film thickness and structure, and assessed by profilometry, Raman spectroscopy, X-ray diffraction and atomic force microscopy. The system demonstrated is useful to obtain crystalline films with controllable thicknesses.

SILAR Deposition of Metal Oxide Nanostructured Films

Methods for the fabrication of thin films with well controlled structure and properties are of great importance for the development of functional devices for a large range of applications. SILAR, the acronym for Successive Ionic Layer Adsorption and Reaction, is an evolution and combination of two other deposition methods, the Atomic Layer Deposition and Chemical Bath Deposition. Due to a relative simplicity and low cost, this method has gained increasing interest in the scientific community. There are, however, several aspects related to the influence of the many parameters involved, which deserve further deepening. In this review article, the basis of the method, its application to the fabrication of thin films, the importance of experimental parameters, and some recent advances in the application of oxide films are reviewed. At first the fundamental theoretical bases and experimental concepts of SILAR are discussed. Then, the fabrication of chalcogenides and metal oxides is reviewed, with special emphasis to metal oxides, trying to extract general information on the effect of experimental parameters on structural, morphological and functional properties. Finally, recent advances in the application of oxide films prepared by SILAR are described, focusing on supercapacitors, transparent electrodes, solar cells, and photoelectrochemical devices.

High-rate transition metal-based cathode materials for battery-supercapacitor hybrid devices

With the rapid development of portable electronic devices, electric vehicles and large-scale grid energy storage devices, there is a need to enhance the specific energy density and specific power density of related electrochemical devices to meet the fast-growing requirements of energy storage. Battery-supercapacitor hybrid devices (BSHDs), combining the high-energy-density feature of batteries and the high-power-density properties of supercapacitors, have attracted mass attention in terms of energy storage. However, the electrochemical performances of cathode materials for BSHDs are severely limited by poor electrical conductivity and ion transport kinetics. As the rich redox reactions induced by transition metal compounds are able to offer high specific capacity, they are an ideal choice of cathode materials. Therefore, this paper reviews the currently advanced progress of transition metal compound-based cathodes with high-rate performance in BSHDs. We discuss some efficient strategies of enhancing the rate performance of transition metal compounds, including developing intrinsic electrode materials with high conductivity and fast ion transport; modifying materials, such as inserting defects and doping; building composite structures and 3D nano-array structures; interfacial engineering and catalytic effects. Finally, some suggestions are proposed for the potential development of cathodes for BSHDs, which may provide a reference for significant progress in the future.

Annealing effects on structural and photovoltaic properties of the dip-SILAR-prepared bismuth oxyhalides (BiOI, Bi7O9I3, Bi5O7I) films

Bismuth oxyhalides are becoming a promising contender for photovoltaic applications due to its non-toxic nature and decent optical properties. This study mainly deals with clarifying the effects of phase transformations on the structure, optical, and electrical properties of BiOI thin film prepared via dip-successive ionic layer adsorption and reaction (SILAR) method at different annealing temperatures ranging from 100 to 400 °C. Therefore, significant phase transformations (i.e., the existence of Bi7O9I3 and Bi5O7I have been confirmed at 300 °C and 400 °C, respectively) appeared in the produced films, which were mainly due to the change of annealing temperatures. The experimental results confirmed that produced films achieved the maximum current density and efficiency and minimum current density and efficiency at 100 °C and 400 °C, respectively. Experimental results were also showed that with increasing the annealing temperature from 100 to 400 °C, the indirect bandgap risen from 1.77 to 2.96 eV while the crystallite size decreased from 17.62 to 12.99 nm. The energy band diagram with electrolyte explained the observed poor electrical properties during the phase transformation. Hence, this result will add positive impacts on the new information on findings for the dip-SILAR-prepared BiOI photovoltaic cells.

Effect of the molar concentration of pyrrole monomer on the rate of polymerization, growth and hence the electrochemical behavior of highly pristine PPy flexible electrodes

The rate of polymerization decides growth and hence electrochemical properties of the electrodes of conducting polymers synthesized by SILAR method are affected by molar concentration of the precursors. Present work describes the effect of molar concentration of Pyrrole monomer on the rate of polymerization and hence the electrochemical performance of highly pristine PPy flexible electrodes. 304 grade flexible stainless steel strips were coated with the PPy using aqueous solutions of 0.025M, 0.05 M and 0.1M pyrrole in 0.5 M H₂SO₄ separately and 30% H₂O₂. XRD patterns substantiate the formation of amorphous PPy. The peak at 1560 cm⁻¹ in FTIR confirms the formation of polypyrrole. SEM images of the FEs prepared using different molar concentration shows gradual superficial growth. All FEs were electrochemically analyzed for their supercapacitive performance by the electrochemical techniques like cyclic voltammetry, galvanostatic charge discharge study and electrochemical impedance spectroscopy. It was found that, the specific capacitance increases with molar concentration of pyrrole. The pristine PPy FEs prepared with 0.1 M Pyrrole exhibit specific capacitance as high as 899.14 Fg^-1 at 5 mVs^-1 in 0.2 M Na₂SO₄.