Stacked Cu1.8S nanoplatelets as counter electrode for quantum dot-sensitized solar cell

It is found that the electrocatalytic activity of Cu2-xS thin films used in quantum dot-sensitized solar cells (QDSSCs) as counter electrode (CE) for the reduction of polysulfide electrolyte depends on the surface active sulfide and disulfide species and the deficiency of Cu. The preferential bonding between Cu2+ and S2-, leading to the selective formation of a Cu1.8S stacked platelet-like morphology, is determined by the cetyl trimethyl ammonium bromide surfactant and deposition temperature; the crab-like Cu-S coordination bond formed dictates the surface area to volume ratio of the Cu1.8S thin films and their electrocatalytic activity. The Cu deficiency enhances the conductivity of the Cu1.8S thin films, which exhibit near-infrared localized surface plasmon resonance due to free carriers, and UV-vis absorption spectra show an excitonic effect due to the quantum size effect. When these Cu1.8S thin films were employed as CEs in QDSSCs, a robust photoconversion efficiency of 5.2% was obtained for the film deposited at 60 °C by a single-step chemical bath deposition method

Phase Transformation and Evolution of Localized Surface Plasmon Resonance in Cu_2–<i>x</i>S Thin Films Deposited at 60 °C

Cu_2–<i>x</i>S (0 ≤ x ≤ 1) thin films deposited at low temperatures (<95 °C) have rich polymorphs due to small differences in Gibbs free energy of formation, which is critical for understanding their fundamental properties. In this work, phase transformation from djurleite to covellite is obtained by simple chemical bath deposition (CBD) without using oxidizing/reducing agents. Cu_2–<i>x</i>S thin films synthesized using cetyltrimethylammonium bromide as a surfactant at 60 °C for different deposition time exhibit red shift in optical absorption due to quantum size effect and blue shift in localized surface plasmon resonance in the near-infrared region originating from increased copper vacancy. The surface morphology of the Cu_2–<i>x</i>S thin films is influenced by the surfactant, which in turn alters the optoelectronics properties. The preferential bonding between Cu and S is determined by hydrolysis of thioacetamide to release sulfides (S^2–) and disulfides (S₂^2–) and the kinetics to reduce Cu²⁺ to Cu⁺ leading to mixed phase formation and an increase in surface to volume ratio. Through X-ray photoelectron spectroscopy and X-ray absorption near edge structure analysis, it is confirmed that both Cu²⁺ and S^2– are reduced with time of deposition and form covellite Cu–S₂^2––Cu bonds

Engineering redox active sites enriched 3D-on-2D bimetallic double layered hydroxide electrode for supercapatteries

DOI link format: http://dx.doi.org/10.1016/j.mtener.2022.101182 © 2022 Elsevier. This manuscript version is made available under the CC-BY-NC-ND 4.0 license http://creativecommons.org/licenses/by-nc-nd/4.0/The functionalization of structural nanoengineered battery-type electrodes has aided the emergence of supercapattery (SCp) subclass, which enables a wide range of applications. Herein, our research work provides a platform for two-step fabrication of nanoengineered 3D-on-2D structure as a promising approach to obtain high-performance battery-type electrodes. The hierarchical 2D NiCo bimetallic LDH NC(12)40 electrode was fabricated using electrodeposition, while the nanoengineered 3D ZIF-67 on 2D LDH electrode was achieved via pseudomorphic replication techniques. The fabricated 3D-on-2D NC(12)40-30 electrode reveals a maximum areal capacity of 1044 mC cm-2 at a current density of 4 mA cm-2 in 6 M KOH electrolyte. Furthermore, NC(12)40-30//AC was integrated as a SCp device, achieving a maximum specific capacitance of 63 F/g and maximum specific energy and power of 20.5 W/h/kg and 8522.7 W/kg, respectively, with improved capacitance retention (85%) even after 10,000 cycles. Thus, the assembled SCp coin cell displays 18-LED illumination in four different commercial LED colors, indicating the viability of the battery-type electrode for SCp development.This research was supported by Basic Science Research Program through the National Research Foundation of Korea (NRF) funded by the Ministry of Education (NRF-2014R1A6A1030419) and by the National Research Foundation of Korea (NRF) Grant funded by the Korean government (MSIT) (No. 2020112382). This work has been partially supported by the Spanish government under project PID2019-109215RB-C41 (SCALED).Peer ReviewedPostprint (author's final draft

Two-dimensional synergistic interfacial orientation on tin oxide-reinforced cobalt carbonate hydroxide heterostructures for high-performance energy storage

This document is the Accepted Manuscript version of a Published Work that appeared in final form in ACS Appl. Mater. Interfaces, copyright © 2023 after peer review and technical editing by the publisher. To access the final edited and published work seehttps://pubs.acs.org/doi/10.1021/acsami.3c10336.A hierarchical cobalt carbonate hydroxide (CCH) nanostructure with outstanding electrochemical kinetics and structural stability for energy storage is largely unknown. Herein, we report tin oxide-functionalized CCH surface-enabled unique two-dimensional (2D) interlayered heterostructures that promote high conductivity with more electroactive sites to maximize redox reactions. A simple electrodeposition technique was utilized to construct the hierarchical 2D CCH electrode, while a surface-reinforced method was employed to fabricate the 2D interlayered SnO on CCH. The fabricated SnO@CCH-8 electrode showed a maximum areal capacity of 720 mC cm–2 (specific capacitance of 515 F g–1) at a current density of 1 mA cm–2 in 3 M KOH electrolyte. The obtained results indicate that the synergetic effect of SnO in the CCH network delivers an efficient charge transfer pathway to achieve high-performance energy storage. Moreover, SnO@CCH-8//AC was devised as a hybrid supercapacitor (HSC), ensuring a maximum specific capacitance of 129 F g–1 and maximum specific energy and power of 40.25 W h kg–1 and 9000 W kg–1, respectively, with better capacitance retention (94%) even beyond 10,000 cycles. To highlight the excellent performance in real-time studies, the HSC was constructed using a coin cell and displayed to power 21 light-emitting diodes (LEDs).Peer ReviewedPostprint (author's final draft

Phase transition kinetics and surface binding states of methylammonium lead iodide perovskite

We have presented a detailed analysis of the phase transition kinetics and binding energy states of solution processed methylammonium lead iodide (MAPbI3) thin films prepared at ambient conditions and annealed at different elevated temperatures. It is the processing temperature and environmental conditions that predominantly control the crystal structure and surface morphology of MAPbI3 thin films. The structural transformation from tetragonal to cubic occurs at 60 °C with a 30 minute annealing time while the 10 minute annealed films posses a tetragonal crystal structure. The transformed phase is greatly intact even at the higher annealing temperature of 150 °C and after a time of 2 hours. The charge transfer interaction between the Pb 4f and I 3d oxidation states is quantified using XPS

Optical Fiber Sensors: Working Principle, Applications, and Limitations

Fiber‐optic technology emerged originally for applications in data transmission and telecommunications. However, sensors based on fiber‐optics have been developed rapidly because of their excellent sensing performances and capability to function in remote and harsh environments. The usage of fiber‐optic sensors has flourished in many fields over the past 30 years due to the fiber‐optic's inherent advantages: cost‐effectiveness, miniaturized size, light weight, and immunity to electromagnetic interference. This work reviews the fiber‐optic sensors based on Bragg gratings, long period gratings, interferometers, surface plasmon resonance, fluorescence, and light diffusion. Brief theory of sensing principle, fabrication method, applications, advantages and disadvantages of the different fiber‐optic sensors, are addressed. Recent progress in numerous sensing fields, including environmental, industrial, and biomedical are discussed for each class of fiber‐optic sensors. The review highlights the methods and techniques used to overcome the sensing challenges. Finally, prospect of future developments of fiber‐optic sensors is summarized