Research

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13 pages, 3835 KiB

Open AccessArticle

Preparation of S-C₃N₄/AgCdS Z-Scheme Heterojunction Photocatalyst and Its Effectively Improved Photocatalytic Performance

by Yuhong Lin, Zhuoyuan Chen, Chang Feng, Li Ma, Jiangping Jing, Jian Hou, Likun Xu, Mingxian Sun and Dongchu Chen

Molecules 2024, 29(9), 1931; https://doi.org/10.3390/molecules29091931 - 24 Apr 2024

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Abstract

In this study, S-doped graphitic carbon nitride (S-C₃N₄) was prepared using the high-temperature polymerization method, and then S-C₃N₄/AgCdS heterojunction photocatalyst was obtained using the chemical deposition method through loading Ag-doped CdS nanoparticles (AgCdS NPs) on [...] Read more.

In this study, S-doped graphitic carbon nitride (S-C₃N₄) was prepared using the high-temperature polymerization method, and then S-C₃N₄/AgCdS heterojunction photocatalyst was obtained using the chemical deposition method through loading Ag-doped CdS nanoparticles (AgCdS NPs) on the surface of S-C₃N₄. Experimental results show that the AgCdS NPs were evenly dispersed on the surface of S-C₃N₄, indicating that a good heterojunction structure was formed. Compared to S-C₃N₄, CdS, AgCdS and S-C₃N₄/CdS, the photocatalytic performance of S-C₃N₄/AgCdS has been significantly improved, and exhibits excellent photocatalytic degradation performance of Rhodamine B and methyl orange. The doping of Ag in collaboration with the construction of a Z-scheme heterojunction system promoted the effective separation and transport of the photogenerated carriers in S-C₃N₄/AgCdS, significantly accelerated its photocatalytic reaction process, and thus improved its photocatalytic performance. Full article

(This article belongs to the Special Issue Electroanalysis of Biochemistry and Material Chemistry)

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10 pages, 5246 KiB

Open AccessArticle

Surface Charge Effects for the Hydrogen Evolution Reaction on Pt(111) Using a Modified Grand-Canonical Potential Kinetics Method

by Shaoyu Kong, Min Ouyang, Yi An, Wei Cao and Xiaobo Chen

Molecules 2024, 29(8), 1813; https://doi.org/10.3390/molecules29081813 - 17 Apr 2024

Viewed by 334

Abstract

Surface charges of catalysts have important influences on the thermodynamics and kinetics of electrochemical reactions. Herein, we develop a modified version of the grand-canonical potential kinetics (GCP-K) method based on density functional theory (DFT) calculations to explore the effect of surface charges on [...] Read more.

Surface charges of catalysts have important influences on the thermodynamics and kinetics of electrochemical reactions. Herein, we develop a modified version of the grand-canonical potential kinetics (GCP-K) method based on density functional theory (DFT) calculations to explore the effect of surface charges on reaction thermodynamics and kinetics. Using the hydrogen evolution reaction (HER) on the Pt(111) surface as an example, we show how to track the change of surface charge in a reaction and how to analyze its influence on the kinetics. Grand-canonical calculations demonstrate that the optimum hydrogen adsorption energy on Pt under the standard hydrogen electrode condition (SHE) is around −0.2 eV, rather than 0 eV established under the canonical ensemble, due to the high density of surface negative charges. By separating the surface charges that can freely exchange with the external electron reservoir, we obtain a Tafel barrier that is in good agreement with the experimental result. During the Tafel reaction, the net electron inflow into the catalyst leads to a stabilization of canonical energy and a destabilization of the charge-dependent grand-canonical component. This study provides a practical method for obtaining accurate grand-canonical reaction energetics and analyzing the surface charge induced changes. Full article

(This article belongs to the Special Issue Electroanalysis of Biochemistry and Material Chemistry)

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10 pages, 4904 KiB

Open AccessArticle

Investigation of the Performance of Hastelloy X as Potential Bipolar Plate Materials in Proton Exchange Membrane Fuel Cells

by Jiacheng Zhong, Zimeng Liu, Meng Zhang, Feng Liu, Wenjin Li, Beirui Hou, Wenmin Zhang, Chunwang Zhao and Mingxing Gong

Molecules 2024, 29(6), 1299; https://doi.org/10.3390/molecules29061299 - 14 Mar 2024

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Abstract

The phase, mechanical properties, corrosion resistance, hydrophobicity, and interfacial contact resistance of Hastelloy X were investigated to evaluate its performance in proton exchange membrane fuel cells (PEMFCs). For comparison, the corresponding performance of 304 stainless steel (304SS) was also tested. Hastelloy X exhibited [...] Read more.

The phase, mechanical properties, corrosion resistance, hydrophobicity, and interfacial contact resistance of Hastelloy X were investigated to evaluate its performance in proton exchange membrane fuel cells (PEMFCs). For comparison, the corresponding performance of 304 stainless steel (304SS) was also tested. Hastelloy X exhibited a single-phase face-centered cubic structure with a yield strength of 445.5 MPa and a hardness of 262.7 HV. Both Hastelloy X and 304SS exhibited poor hydrophobicity because the water contact angles were all below 80°. In a simulated PEMFC working environment (0.5 M H₂SO₄ + 2 ppm HF, 80 °C, H₂), Hastelloy X exhibited better corrosion resistance than 304SS. At 140 N·cm⁻², the interfacial contact resistance of Hastelloy X can reach as low as 7.4 mΩ·cm². Considering its overall performance, Hastelloy X has better potential application than 304SS as bipolar plate material in PEMFCs. Full article

(This article belongs to the Special Issue Electroanalysis of Biochemistry and Material Chemistry)

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10 pages, 1622 KiB

Open AccessArticle

Li⁺ Conduction in a Polymer/Li_1.5Al_0.5Ge_1.5(PO₄)₃ Solid Electrolyte and Li-Metal/Electrolyte Interface

by Qinghui Li, Xiaofen Wang, Linlin Wang, Shyuan Zhu, Qingdong Zhong, Yuanyuan Li and Qiongyu Zhou

Molecules 2023, 28(24), 8029; https://doi.org/10.3390/molecules28248029 - 10 Dec 2023

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Abstract

The solid oxide electrolyte Li_1.5Al_0.5Ge_1.5(PO₄)₃ (LAGP) with a NASICON structure has a high bulk ionic conductivity of 10⁻⁴ S cm⁻¹ at room temperature and good stability in the air because of the [...] Read more.

The solid oxide electrolyte Li_1.5Al_0.5Ge_1.5(PO₄)₃ (LAGP) with a NASICON structure has a high bulk ionic conductivity of 10⁻⁴ S cm⁻¹ at room temperature and good stability in the air because of the strong P⁵⁺-O²⁻ covalence bonding. However, the Ge⁴⁺ ions in LAGP are quickly reduced to Ge³⁺ on contact with the metallic lithium anode, and the LAGP ceramic has insufficient physical contact with the electrodes in all-solid-state batteries, which limits the large-scale application of the LAGP electrolyte in all-solid-state Li-metal batteries. Here, we prepared flexible PEO/LiTFSI/LAGP composite electrolytes, and the introduction of LAGP as a ceramic filler in polymer electrolytes increases the total ionic conductivity and the electrochemical stability of the composite electrolyte. Moreover, the flexible polymer shows good contact with the electrodes, resulting in a small interfacial resistance and stable cycling of all-solid-state Li-metal batteries. The influence of the external pressure and temperature on Li⁺ transfer across the Li/electrolyte interface is also investigated. Full article

(This article belongs to the Special Issue Electroanalysis of Biochemistry and Material Chemistry)

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14 pages, 5389 KiB

Open AccessArticle

Photoelectrocatalytic Processes of TiO₂ Film: The Dominating Factors for the Degradation of Methyl Orange and the Understanding of Mechanism

by Yuhui Xiong, Sijie Ma, Xiaodong Hong, Jiapeng Long and Guangjin Wang

Molecules 2023, 28(24), 7967; https://doi.org/10.3390/molecules28247967 - 06 Dec 2023

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Abstract

Various thicknesses of TiO₂ films were prepared by the sol–gel method and spin-coating process. These prepared TiO₂ films exhibit thickness-dependent photoelectrochemical performance. The 1.09-μm-thickTiO₂ film with 20 spin-coating layers (TiO₂-20) exhibits the highest short circuit current of 0.21 [...] Read more.

Various thicknesses of TiO₂ films were prepared by the sol–gel method and spin-coating process. These prepared TiO₂ films exhibit thickness-dependent photoelectrochemical performance. The 1.09-μm-thickTiO₂ film with 20 spin-coating layers (TiO₂-20) exhibits the highest short circuit current of 0.21 mAcm⁻² and open circuit voltage of 0.58 V among all samples and exhibits a low PEC reaction energy barrier and fast kinetic process. Photoelectrocatalytic (PEC) degradation of methyl orange (MO) by TiO₂ films was carried out under UV light. The roles of bias, film thickness, pH value, and ion properties were systematically studied because they are the four most important factors dominating the PEC performance of TiO₂ films. The optimized values of bias, film thickness, and pH are 1.0 V, 1.09 μm, and 12, respectively, which were obtained according to the data of the PEC degradation of MO. The effect of ion properties on the PEC efficiency of TiO₂-20 was also analyzed by using halide as targeted ions. The “activated” halide ions significantly promoted the PEC efficiency and the order was determined as Br > Cl > F. The PEC efficiency increased with increasing Cl content, up until the optimized value of 30 × 10⁻³ M. Finally, a complete degradation of MO by TiO₂-20 was achieved in 1.5 h, with total optimization of the four factors: 1.0 V bias, 1.09-μm-thick, pH 12, and 30 × 10⁻³ M Cl ion content. The roles of reactive oxygen species and electric charge of photoelectrodes were also explored based on photoelectrochemical characterizations and membrane-separated reactors. Hydrogen peroxide, superoxide radical, and hydroxyl radical were found responsible for the decolorization of MO. Full article

(This article belongs to the Special Issue Electroanalysis of Biochemistry and Material Chemistry)

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17 pages, 5260 KiB

Open AccessArticle

Electrospun Nanofibrous Conduit Filled with a Collagen-Based Matrix (ColM) for Nerve Regeneration

by Yuanjing Hou, Xinyu Wang, Yiyu Wang, Xia Chen, Benmei Wei, Juntao Zhang, Lian Zhu, Huizhi Kou, Wenyao Li and Haibo Wang

Molecules 2023, 28(22), 7675; https://doi.org/10.3390/molecules28227675 - 20 Nov 2023

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Abstract

Traumatic nerve defects result in dysfunctions of sensory and motor nerves and are usually accompanied by pain. Nerve guidance conduits (NGCs) are widely applied to bridge large-gap nerve defects. However, few NGCs can truly replace autologous nerve grafts to achieve comprehensive neural regeneration [...] Read more.

Traumatic nerve defects result in dysfunctions of sensory and motor nerves and are usually accompanied by pain. Nerve guidance conduits (NGCs) are widely applied to bridge large-gap nerve defects. However, few NGCs can truly replace autologous nerve grafts to achieve comprehensive neural regeneration and function recovery. Herein, a three-dimensional (3D) sponge-filled nanofibrous NGC (sf@NGC) resembling the structure of native peripheral nerves was developed. The conduit was fabricated by electrospinning a poly(L-lactide-co-glycolide) (PLGA) membrane, whereas the intraluminal filler was obtained by freeze-drying a collagen-based matrix (ColM) resembling the extracellular matrix. The effects of the electrospinning process and of the composition of ColM on the physicochemical performance of sf@NGC were investigated in detail. Furthermore, the biocompatibility of the PLGA sheath and ColM were evaluated. The continuous and homogeneous PLGA nanofiber membrane had high porosity and tensile strength. ColM was shown to exhibit an ECM-like architecture characterized by a multistage pore structure and a high porosity level of over 70%. The PLGA sheath and ColM were shown to possess stagewise degradability and good biocompatibility. In conclusion, sf@NGC may have a favorable potential for the treatment of nerve reconstruction. Full article

(This article belongs to the Special Issue Electroanalysis of Biochemistry and Material Chemistry)

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12 pages, 4364 KiB

Open AccessCommunication

Mechanistic Study on the Corrosion of (La,Sr)(Co,Fe)O_3-δ Cathodes Induced by CO₂

by Na Xu, Shijiao Zhang, Qiongyu Zhou, Hairui Wang, Lina Zhao and Zhanlin Xu

Molecules 2023, 28(22), 7490; https://doi.org/10.3390/molecules28227490 - 08 Nov 2023

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Abstract

Solid Oxide Fuel Cell (SOFC) cathodes operating in ambient atmospheric conditions inevitably encounter CO₂ contamination, leading to sustained performance deterioration. In this investigation, we examined the impact of CO₂ on three variants of (La,Sr)(Co,Fe)O_3-δ cathodes and employed the distribution of [...] Read more.

Solid Oxide Fuel Cell (SOFC) cathodes operating in ambient atmospheric conditions inevitably encounter CO₂ contamination, leading to sustained performance deterioration. In this investigation, we examined the impact of CO₂ on three variants of (La,Sr)(Co,Fe)O_3-δ cathodes and employed the distribution of relaxation times method to distinguish distinct electrochemical processes based on impedance spectra analysis. We meticulously analyzed and discussed the corrosion resistance of these (La,Sr)(Co,Fe)O_3-δ cathodes under high CO₂ concentrations, relying on the experimental data. Electrochemical impedance spectroscopy results revealed that La_0.6Sr_0.4Co_0.2Fe_0.8O_3-δ (LSCF−6428), La_0.4Sr_0.6Co_0.2Fe_0.8O_3-δ (LSCF−4628), and La_0.4Sr_0.6Co_0.2Fe_0.7Nb_0.1O_3-δ (LSCFN−46271) cathodes exhibited persistent degradation when exposed to CO₂ at temperatures of 650 °C or 800 °C during the durability-testing period. An increase in electrode polarization resistance was observed upon CO₂ introduction to the electrode, but electrode performance recovered upon returning to a pure air environment. Furthermore, X-ray diffraction and scanning electron microscopy analyses confirmed that CO₂ did not cause permanent damage to the (La,Sr)(Co,Fe)O_3-δ cathodes. These findings indicate that the (La,Sr)(Co,Fe)O_3-δ cathodes exhibit excellent resistance to CO₂-induced corrosion. Full article

(This article belongs to the Special Issue Electroanalysis of Biochemistry and Material Chemistry)

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11 pages, 6188 KiB

Open AccessArticle

Gallium-Doped Hydroxyapatite: Shape Transformation and Osteogenesis Activity

by Wei Shuai, Jianguo Zhou, Chen Xia, Sirui Huang, Jie Yang, Lin Liu and Hui Yang

Molecules 2023, 28(21), 7379; https://doi.org/10.3390/molecules28217379 - 01 Nov 2023

Viewed by 955

Abstract

In this study, we employed a chemical precipitation method to successfully synthesize nanoparticles of gallium-doped hydroxyapatite (Ga-HAp). The microstructure of Ga-HAp was precisely tailored by modulating the concentration of gallium ions. Our findings unequivocally demonstrate that gallium ions exert a pronounced inhibitory influence [...] Read more.

In this study, we employed a chemical precipitation method to successfully synthesize nanoparticles of gallium-doped hydroxyapatite (Ga-HAp). The microstructure of Ga-HAp was precisely tailored by modulating the concentration of gallium ions. Our findings unequivocally demonstrate that gallium ions exert a pronounced inhibitory influence on the growth of HAp crystals, and this inhibitory potency exhibits a direct correlation with the concentration of gallium. Furthermore, gallium ions facilitate the metamorphosis of HAp nanoparticles, transitioning them from nanoneedles to nanosheets. It is worth noting, however, that gallium ions exhibit a limited capacity to substitute for calcium ions within the crystal lattice of HAp, with the maximum substitution rate capped at 4.85%. Additionally, gallium plays a pivotal role in constraining the release of ions from HAp, and this behavior remains consistent across samples with varying Ga doping concentrations. Our in vitro experiments confirm that Ga-doped HAp amplifies both the proliferation and osteogenic differentiation of bone marrow mesenchymal stem cells. Full article

(This article belongs to the Special Issue Electroanalysis of Biochemistry and Material Chemistry)

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15 pages, 3574 KiB

Open AccessArticle

High Hardness, Excellent Hydrophobicity, and Favorable Corrosion Resistance of Plasma-Sprayed FeCrMoSi Amorphous Coatings on 304 Stainless Steel

by Jiacheng Zhong, Beirui Hou, Wenmin Zhang, Shitao Zhang, Yuantao Zhao, Chunwang Zhao and Wenge Li

Molecules 2023, 28(18), 6718; https://doi.org/10.3390/molecules28186718 - 20 Sep 2023

Viewed by 723

Abstract

The FeCrMoSi amorphous coatings were fabricated on the surface of a 304 stainless steel (SS) base material using atmospheric plasma spraying. A comprehensive investigation was carried out to evaluate the structure, morphology, adhesion to base material, hardness, hydrophobicity, interfacial contact resistance, and corrosion [...] Read more.

The FeCrMoSi amorphous coatings were fabricated on the surface of a 304 stainless steel (SS) base material using atmospheric plasma spraying. A comprehensive investigation was carried out to evaluate the structure, morphology, adhesion to base material, hardness, hydrophobicity, interfacial contact resistance, and corrosion resistance of the coatings. The results show a remarkable hardness of 1180.1 HV, a strong bond strength of up to 64.3 N/mm², and excellent hydrophobicity with a water contact angle reaching 141.2°. Additionally, in an acidic environment with fluoride ions (0.5 M H₂SO₄ + 2 ppm HF, 80 °C), the FeCrMoSi amorphous coating demonstrated superior corrosion resistance compared with 304 SS while maintaining similar electroconductibility. Detailed analysis of the structural characteristics and corrosion resistance of FeCrMoSi amorphous coatings provided valuable insights into their mechanics. These promising results signify a bright future for FeCrMoSi amorphous coatings in various industrial sectors, including transportation, petroleum, and electric power industries. Full article

(This article belongs to the Special Issue Electroanalysis of Biochemistry and Material Chemistry)

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Review

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25 pages, 12420 KiB

Open AccessReview

Progress in Promising Semiconductor Materials for Efficient Photoelectrocatalytic Hydrogen Production

by Weisong Fu, Yan Zhang, Xi Zhang, Hui Yang, Ruihao Xie, Shaoan Zhang, Yang Lv and Liangbin Xiong

Molecules 2024, 29(2), 289; https://doi.org/10.3390/molecules29020289 - 05 Jan 2024

Viewed by 1250

Abstract

Photoelectrocatalytic (PEC) water decomposition provides a promising method for converting solar energy into green hydrogen energy. Indeed, significant advances and improvements have been made in various fundamental aspects for cutting-edge applications, such as water splitting and hydrogen production. However, the fairly low PEC [...] Read more.

Photoelectrocatalytic (PEC) water decomposition provides a promising method for converting solar energy into green hydrogen energy. Indeed, significant advances and improvements have been made in various fundamental aspects for cutting-edge applications, such as water splitting and hydrogen production. However, the fairly low PEC efficiency of water decomposition by a semiconductor photoelectrode and photocorrosion seriously restrict the practical application of photoelectrochemistry. In this review, the mechanisms of PEC water decomposition are first introduced to provide a solid understanding of the PEC process and ensure that this review is accessible to a wide range of readers. Afterwards, notable achievements to date are outlined, and unique approaches involving promising semiconductor materials for efficient PEC hydrogen production, including metal oxide, sulfide, and graphite-phase carbon nitride, are described. Finally, four strategies which can effectively improve the hydrogen production rate—morphological control, doping, heterojunction, and surface modification—are discussed. Full article

(This article belongs to the Special Issue Electroanalysis of Biochemistry and Material Chemistry)

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19 pages, 3566 KiB

Open AccessReview

Research Progress of Perovskite-Based Bifunctional Oxygen Electrocatalyst in Alkaline Conditions

by Kailin Fu, Weijian Chen, Feng Jiang, Xia Chen and Jianmin Liu

Molecules 2023, 28(20), 7114; https://doi.org/10.3390/molecules28207114 - 16 Oct 2023

Cited by 1 | Viewed by 1115

Abstract

In light of the depletion of conventional energy sources, it is imperative to conduct research and development on sustainable alternative energy sources. Currently, electrochemical energy storage and conversion technologies such as fuel cells and metal-air batteries rely heavily on precious metal catalysts like [...] Read more.

In light of the depletion of conventional energy sources, it is imperative to conduct research and development on sustainable alternative energy sources. Currently, electrochemical energy storage and conversion technologies such as fuel cells and metal-air batteries rely heavily on precious metal catalysts like Pt/C and IrO₂, which hinders their sustainable commercial development. Therefore, researchers have devoted significant attention to non-precious metal-based catalysts that exhibit high efficiency, low cost, and environmental friendliness. Among them, perovskite oxides possess low-cost and abundant reserves, as well as flexible oxidation valence states and a multi-defect surface. Due to their advantageous structural characteristics and easily adjustable physicochemical properties, extensive research has been conducted on perovskite-based oxides. However, these materials also exhibit drawbacks such as poor intrinsic activity, limited specific surface area, and relatively low apparent catalytic activity compared to precious metal catalysts. To address these limitations, current research is focused on enhancing the physicochemical properties of perovskite-based oxides. The catalytic activity and stability of perovskite-based oxides in Oxygen Reduction Reaction/Oxygen Evolution Reaction (ORR/OER) can be enhanced using crystallographic structure tuning, cationic regulation, anionic regulation, and nano-processing. Furthermore, extensive research has been conducted on the composite processing of perovskite oxides with other materials, which has demonstrated enhanced catalytic performance. Based on these different ORR/OER modification strategies, the future challenges of perovskite-based bifunctional oxygen electrocatalysts are discussed alongside their development prospects. Full article

(This article belongs to the Special Issue Electroanalysis of Biochemistry and Material Chemistry)

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