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Multifunctional Metal Oxides: Synthesis and Applications
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Multifunctional Metal Oxides: Synthesis and Applications

A special issue of Molecules (ISSN 1420-3049). This special issue belongs to the section "Inorganic Chemistry".

Deadline for manuscript submissions: closed (1 February 2024) | Viewed by 12220

Special Issue Editor

Prof. Dr. Yanxin Chen

E-Mail Website
Guest Editor
Fujian Institute of Research on the Structure of Matter, Chinese Academy of Sciences, Fuzhou, China
Interests: photochemical/photoelectrochemical energy conversion; photocatalysis and photo-reforming; self-organized TiO2 nanotube arrays; direct ethanol fuel cells; electrochemically shape-controlled synthesis
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

In past decades, we have witnessed a rapid depletion of natural energy sources and the production of tons of waste polluting the environment. In recent years, as a renewable and sustainable energy source, solar-driven water splitting and the reduction of carbon dioxide (CO2) with photoelectrochemical (PEC) cells has been studied extensively, since the use of these cells represents a promising method to simultaneously tackle the energy crisis and environmental issues. Their use produces hydrogen in a clean and sustainable way, and converts CO2 into fuels or chemicals. This Special Issue will serve as a resource or guideline for researchers who are currently focusing on multifunctional metal oxides (MMO), as well as for those who are interested in versatile semiconductor-based PEC applications. Because of their importance and future prospects, a number of architectures with their own features have been formed by various synthesis and growth methods. This Special Issue will present some of the newest developments in the above research area, with the aim of fostering further scientific discussion of the true potential of this topic, encouraging future research.

Prof. Dr. Yanxin Chen
Guest Editor

Manuscript Submission Information

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Keywords

  • photoelectrochemical (PEC)
  • reduction of carbon dioxide (CO2)
  • solar-driven water splitting
  • multifunctional metal oxides (MMO)

Published Papers (9 papers)

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Research

12 pages, 4440 KiB  
Article
MOF-Derived CeO2 Nanorod as a Separator Coating Enabling Enhanced Performance for Lithium–Sulfur Batteries
by Hao Xiao, Jian Qin, Haodong Wang, Xiaoxu Lai, Pei Shi, Chi Chen and Dan Sun
Molecules 2024, 29(8), 1852; https://doi.org/10.3390/molecules29081852 - 18 Apr 2024
Viewed by 399
Abstract
The deployment of Li–S batteries in the commercial sector faces obstacles due to their low electrical conductivity, slow redox reactions, quick fading of capacity, and reduced coulombic efficiency. These issues stem from the “shuttle effect” associated with lithium polysulfides (LiPSs). In this work, [...] Read more.
The deployment of Li–S batteries in the commercial sector faces obstacles due to their low electrical conductivity, slow redox reactions, quick fading of capacity, and reduced coulombic efficiency. These issues stem from the “shuttle effect” associated with lithium polysulfides (LiPSs). In this work, a haystack-like CeO2 derived from a cerium-based metal-organic framework (Ce-MOF) is obtained for the modification of a polypropylene separator. The carbon framework and CeO2 coexist in this haystack-like structure and contribute to a synergistic effect on the restriction of LiPSs shuttling. The carbon network enhances electron transfer in the conversion of LiPSs, improving the rate performance of the battery. Moreover, CeO2 enhances the redox kinetics of LiPSs, effectively reducing the “shuttle effect” in Li–S batteries. The Li–S battery with the optimized CeO2 modified separator shows an initial discharge capacity of 870.7 mAh/g at 2 C, maintaining excellent capacity over 500 cycles. This research offers insights into designing functional separators to mitigate the “shuttle effect” in Li–S batteries. Full article
(This article belongs to the Special Issue Multifunctional Metal Oxides: Synthesis and Applications)
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13 pages, 5569 KiB  
Article
Facile Synthesis of Cu-Doped ZnO Nanoparticles for the Enhanced Photocatalytic Disinfection of Bacteria and Fungi
by Ruichun Nan, Shurui Liu, Mengwan Zhai, Mengzhen Zhu, Xiaodong Sun, Yisong Chen, Qiangqiang Pang and Jingtao Zhang
Molecules 2023, 28(20), 7232; https://doi.org/10.3390/molecules28207232 - 23 Oct 2023
Cited by 1 | Viewed by 1194
Abstract
In this study, Cu-doped ZnO was prepared via the facile one-pot solvothermal approach. The structure and composition of the synthesized samples were characterized by XRD (X-ray diffraction), TEM (transmission electron microscopy), and XPS (X-ray photoelectron spectroscopy) analyses, revealing that the synthesized samples consisted [...] Read more.
In this study, Cu-doped ZnO was prepared via the facile one-pot solvothermal approach. The structure and composition of the synthesized samples were characterized by XRD (X-ray diffraction), TEM (transmission electron microscopy), and XPS (X-ray photoelectron spectroscopy) analyses, revealing that the synthesized samples consisted of Cu-doped ZnO nanoparticles. Ultraviolet–visible (UV-vis) spectroscopy analysis showed that Cu-doping significantly improves the visible light absorption properties of ZnO. The photocatalytic capacity of the synthesized samples was tested via the disinfection of Escherichia coli, with the Cu-ZnO presenting enhanced disinfection compared to pure ZnO. Of the synthesized materials, 7% Cu-ZnO exhibited the best photocatalytic performance, for which the size was ~9 nm. The photocurrent density of the 7% Cu-ZnO samples was also significantly higher than that of pure ZnO. The antifungal activity for 7% Cu-ZnO was also tested on the pathogenic fungi of Fusarium graminearum. The macroconidia of F. graminearum was treated with 7% Cu-ZnO photocatalyst for 5 h, resulting in a three order of magnitude reduction at a concentration of 105 CFU/mL. Fluorescence staining tests were used to verify the survival of macroconidia before and after photocatalytic treatment. ICP-MS was used to confirm that Cu-ZnO met national standards for cu ion precipitation, indicating that Cu-ZnO are environmentally friendly materials. Full article
(This article belongs to the Special Issue Multifunctional Metal Oxides: Synthesis and Applications)
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10 pages, 2470 KiB  
Communication
In Situ Observation of Cellular Structure Changes in and Chain Segregations of Anabaena sp. PCC 7120 on TiO2 Films under a Photocatalytic Device
by Xiaoxin Wang, Jingtao Zhang, Qi Li, Ran Jia, Mei Qiao and Wanling Cui
Molecules 2023, 28(20), 7200; https://doi.org/10.3390/molecules28207200 - 20 Oct 2023
Viewed by 557
Abstract
Cyanobacteria outbreaks are serious water pollution events, causing water crises around the world. Photocatalytic disinfection, as an effective approach, has been widely used to inhibit blue algae growth. In this study, a tiny reaction room containing a TiO2 film was designed to [...] Read more.
Cyanobacteria outbreaks are serious water pollution events, causing water crises around the world. Photocatalytic disinfection, as an effective approach, has been widely used to inhibit blue algae growth. In this study, a tiny reaction room containing a TiO2 film was designed to fulfill in situ optical observation of the destruction process of a one-dimensional multicellular microorganism, Anabaena sp. PCC 7120, which is also a typical bacterial strain causing water blooms. It was found that the fragment number increased exponentially with the activation time. The fracture mechanics of the algae chains were hypothesized to be the combining functions of increased local tensile stress originated from the cell contracting as well as the oxidative attacks coming from reactive oxygen species (ROSs). It was assumed that the oxidative species were the root cause of cellular structure changes in and chain fractures of Anabaena sp. PCC 7120 in the photocatalytic inactivation activity. Full article
(This article belongs to the Special Issue Multifunctional Metal Oxides: Synthesis and Applications)
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8 pages, 3680 KiB  
Communication
Trapping an Ester Hydrate Intermediate in a π-Stacked Macrocycle with Multiple Hydrogen Bonds
by Bin Wang, Zi-Ang Nan, Qing Li, Jin Liu, Zi-Xiu Lu, Wei Wang, Zhu Zhuo, Guo-Ling Li and You-Gui Huang
Molecules 2023, 28(15), 5705; https://doi.org/10.3390/molecules28155705 - 28 Jul 2023
Viewed by 768
Abstract
Ester hydrates, as the intermediates of the esterification between acid and alcohol, are very short-lived and challenging to be trapped. Therefore, the crystal structures of ester hydrates have rarely been characterized. Herein, we present that the mono-deprotonated ester hydrates [CH3OSO2 [...] Read more.
Ester hydrates, as the intermediates of the esterification between acid and alcohol, are very short-lived and challenging to be trapped. Therefore, the crystal structures of ester hydrates have rarely been characterized. Herein, we present that the mono-deprotonated ester hydrates [CH3OSO2(OH)2]−, serving as the template for the self-assembly of a π-stacked boat-shaped macrocycle (CH3OSO2(OH)2)0.67(CH3OSO3)1.33@{[ClLCoII]6}·Cl4·13CH3OH·9H2O (1) (L = tris(2-benzimidazolylmethyl) amine), can be trapped in the host by multiple NH···O hydrogen bonds. In the solution of CoCl2, L, and H2SO4 in MeOH, HSO4− reacts with MeOH, producing [CH3OSO3]− via the ester hydrate intermediate of [CH3OSO3(OH)2]−. Both the product and the intermediate serve as the template directing the self-assembly of the π-stacked macrocycle, in which the short-lived ester hydrate is firmly trapped and stabilized, as revealed by single-crystal analysis. Full article
(This article belongs to the Special Issue Multifunctional Metal Oxides: Synthesis and Applications)
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14 pages, 2392 KiB  
Article
Tröger’s Base-Derived Thermally Activated Delayed Fluorescence Dopant for Efficient Deep-Blue Organic Light-Emitting Diodes
by Ze-Ling Wu, Xin Lv, Ling-Yi Meng, Xu-Lin Chen and Can-Zhong Lu
Molecules 2023, 28(12), 4832; https://doi.org/10.3390/molecules28124832 - 17 Jun 2023
Cited by 1 | Viewed by 1145
Abstract
The development of efficient deep-blue emitters with thermally activated delayed fluorescence (TADF) properties is a highly significant but challenging task in the field of organic light-emitting diode (OLED) applications. Herein, we report the design and synthesis of two new 4,10-dimethyl-6H,12H-5,11-methanodibenzo[b,f][1,5]diazocine ( [...] Read more.
The development of efficient deep-blue emitters with thermally activated delayed fluorescence (TADF) properties is a highly significant but challenging task in the field of organic light-emitting diode (OLED) applications. Herein, we report the design and synthesis of two new 4,10-dimethyl-6H,12H-5,11-methanodibenzo[b,f][1,5]diazocine (TB)-derived TADF emitters, TB-BP-DMAC and TB-DMAC, which feature distinct benzophenone (BP)-derived acceptors but share the same dimethylacridin (DMAC) donors. Our comparative study reveals that the amide acceptor in TB-DMAC exhibits a significantly weaker electron-withdrawing ability in comparison to that of the typical benzophenone acceptor employed in TB-BP-DMAC. This disparity not only causes a noticeable blue shift in the emission from green to deep blue but also enhances the emission efficiency and the reverse intersystem crossing (RISC) process. As a result, TB-DMAC emits efficient deep-blue delay fluorescence with a photoluminescence quantum yield (PLQY) of 50.4% and a short lifetime of 2.28 μs in doped film. The doped and non-doped OLEDs based on TB-DMAC display efficient deep-blue electroluminescence with spectral peaks at 449 and 453 nm and maximum external quantum efficiencies (EQEs) of 6.1% and 5.7%, respectively. These findings indicate that substituted amide acceptors are a viable option for the design of high-performance deep-blue TADF materials. Full article
(This article belongs to the Special Issue Multifunctional Metal Oxides: Synthesis and Applications)
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11 pages, 2732 KiB  
Article
Surfactant Additives Containing Hydrophobic Fluorocarbon Chains and Hydrophilic Sulfonate Anion for Highly Reversible Zn Anode
by Jinxian Huang, Zhao Fu, Chuan-Fu Sun and Wenzhuo Deng
Molecules 2023, 28(10), 4177; https://doi.org/10.3390/molecules28104177 - 18 May 2023
Viewed by 1520
Abstract
Aqueous zinc-ion batteries (AZIBs) show enormous potential as a large-scale energy storage technique. However, the growth of Zn dendrites and serious side reactions occurring at the Zn anode hinder the practical application of AZIBs. For the first time, we reported a fluorine-containing surfactant, [...] Read more.
Aqueous zinc-ion batteries (AZIBs) show enormous potential as a large-scale energy storage technique. However, the growth of Zn dendrites and serious side reactions occurring at the Zn anode hinder the practical application of AZIBs. For the first time, we reported a fluorine-containing surfactant, i.e., potassium perfluoro-1-butanesulfonate (PPFBS), as an additive to the 2 M ZnSO4 electrolyte. Benefitting from its hydrophilic sulfonate anion and hydrophobic long fluorocarbon chain, PPFBS can promote the uniform distribution of Zn2+ flux at the anode/electrolyte interface, allowing the Zn/Zn cell to cycle for 2200 h. Furthermore, PPFBS could inhibit side reactions due to the existence of the perfluorobutyl sulfonate (C4F9SO3−) adsorption layer and the presence of C4F9SO3− in the solvation structure of Zn2+. The former can reduce the amount of H2O molecules and SO42− in contact with the Zn anode and C4F9SO3− entering the Zn2+-solvation structure by replacing SO42−. The Zn/Cu cell exhibits a superior average CE of 99.47% over 500 cycles. When coupled with the V2O5 cathode, the full cell shows impressive cycle stability. This work provides a simple, effective, and economical solution to the common issues of the Zn anode. Full article
(This article belongs to the Special Issue Multifunctional Metal Oxides: Synthesis and Applications)
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13 pages, 3061 KiB  
Article
Recovery of Li2CO3 from Spent LiFePO4 by Using a Novel Impurity Elimination Process
by Wen-Lan Chen, Chi Chen, Hao Xiao, Cheng-Wei Chen and Dan Sun
Molecules 2023, 28(9), 3902; https://doi.org/10.3390/molecules28093902 - 05 May 2023
Cited by 2 | Viewed by 2354
Abstract
The large-scale implementations of lithium iron phosphate (LFP) batteries for energy storage systems have been gaining attention around the world due to their quality of high technological maturity and flexible configuration. Unfortunately, the exponential production of LFP batteries is accompanied by an annual [...] Read more.
The large-scale implementations of lithium iron phosphate (LFP) batteries for energy storage systems have been gaining attention around the world due to their quality of high technological maturity and flexible configuration. Unfortunately, the exponential production of LFP batteries is accompanied by an annual accumulation of spent batteries and a premature consumption of the lithium resource. Recycling souring critical battery materials such as Li2CO3 is essential to reduce the supply chain risk and achieve net carbon neutrality goals. During the recovery of Li2CO3, impurity removal is the most crucial step in the hydrometallurgy process of spent LiFePO4, which determines the purity of Li2CO3. By investigating and comparing the results of impurity elimination from the purified Li+-containing liquids with strong and weak alkalis under identical pH conditions, respectively, a strategy based on an alkali mixture has been proposed. The purified Li+-containing liquid was, thereafter, concentrated and sodium carbonate was added in order to precipitate Li2CO3. As a result, a high purity Li2CO3 (99.51%) of battery grade was obtained. LiFePO4 prepared with the recovered Li2CO3 and FePO4 as raw materials also displayed a comparative high capacity and stable cycle performance to the commercial product and further verified the electrochemical activity of the recovered materials. Full article
(This article belongs to the Special Issue Multifunctional Metal Oxides: Synthesis and Applications)
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14 pages, 79283 KiB  
Article
Cerium Synchronous Doping in Anatase for Enhanced Photocatalytic Hydrogen Production from Ethanol-Water Mixtures
by Mei-Hong Tong, Yan-Xin Chen, Tian-Ming Wang, Shi-Wei Lin, Gen Li, Qian-Qian Zhou, Rui Chen, Xia Jiang, Hong-Gang Liao and Can-Zhong Lu
Molecules 2023, 28(6), 2433; https://doi.org/10.3390/molecules28062433 - 07 Mar 2023
Cited by 3 | Viewed by 1849
Abstract
Cerium element with a unique electric structure can be used to modify semiconductor photocatalysts to enhance their photocatalytic performances. In this work, Ce-doped TiO2 (Ce/TiO2) was successfully achieved using the sol-gel method. The structural characterization methods confirm that Ce was [...] Read more.
Cerium element with a unique electric structure can be used to modify semiconductor photocatalysts to enhance their photocatalytic performances. In this work, Ce-doped TiO2 (Ce/TiO2) was successfully achieved using the sol-gel method. The structural characterization methods confirm that Ce was doped in the lattice of anatase TiO2, which led to a smaller grain size. The performance test results show that the Ce doped in anatase TiO2 significantly enhances the charge transport efficiency and broadens the light absorption range, resulting in higher photocatalytic performance. The Ce/TiO2 exhibited a photocurrent density of 10.9 μA/cm2 at 1.0 V vs. Ag/AgCl, 2.5 times higher than that of pure TiO2 (4.3 μA/cm2) under AM 1.5 G light. The hydrogen (H2) production rate of the Ce/TiO2 was approximately 0.33 μmol/h/g, which is more than twice as much as that of the pure anatase TiO2 (0.12 μmol/h/g). This work demonstrates the effect of Ce doping in the lattice of TiO2 for enhanced photocatalytic hydrogen production. Full article
(This article belongs to the Special Issue Multifunctional Metal Oxides: Synthesis and Applications)
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13 pages, 3136 KiB  
Article
Cerium-Doped Iron Oxide Nanorod Arrays for Photoelectrochemical Water Splitting
by Hai-Peng Zhao, Mei-Ling Zhu, Hao-Yan Shi, Qian-Qian Zhou, Rui Chen, Shi-Wei Lin, Mei-Hong Tong, Ming-Hao Ji, Xia Jiang, Chen-Xing Liao, Yan-Xin Chen and Can-Zhong Lu
Molecules 2022, 27(24), 9050; https://doi.org/10.3390/molecules27249050 - 19 Dec 2022
Cited by 4 | Viewed by 1732
Abstract
In this work, a simple one-step hydrothermal method was employed to prepare the Ce-doped Fe2O3 ordered nanorod arrays (CFT). The Ce doping successfully narrowed the band gap of Fe2O3, which improved the visible light absorption performance. [...] Read more.
In this work, a simple one-step hydrothermal method was employed to prepare the Ce-doped Fe2O3 ordered nanorod arrays (CFT). The Ce doping successfully narrowed the band gap of Fe2O3, which improved the visible light absorption performance. In addition, with the help of Ce doping, the recombination of electron/hole pairs was significantly inhibited. The external voltage will make the performance of the Ce-doped sample better. Therefore, the Ce-doped Fe2O3 has reached superior photoelectrochemical (PEC) performance with a high photocurrent density of 1.47 mA/cm2 at 1.6 V vs. RHE (Reversible Hydrogen Electrode), which is 7.3 times higher than that of pristine Fe2O3 nanorod arrays (FT). The Hydrogen (H2) production from PEC water splitting of Fe2O3 was highly improved by Ce doping to achieve an evolution rate of 21 μmol/cm2/h. Full article
(This article belongs to the Special Issue Multifunctional Metal Oxides: Synthesis and Applications)
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