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Advanced Functional Materials for Photo/Electro-Catalysts for Environmental and Energy Applications

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A special issue of Catalysts (ISSN 2073-4344). This special issue belongs to the section "Catalysis for Sustainable Energy".

Deadline for manuscript submissions: closed (30 April 2023) | Viewed by 35518

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Dr. Sekar Karthikeyan

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Guest Editor

Department of Chemistry, SRM Institute of Science and Technology Kattankulathur, India
Interests: material science; surface modification; catalysis; heterogeneous catalysis; sustainable energy; sustainable water

Dr. Boopathy Ramasamy

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Guest Editor

Department of Environment and Sustainability (IMMT), CSIR-Institute of Minerals and Materials Technology, Bhubaneshwar, India
Interests: atmospheric aerosol and its characterization; preparation of low-cost composite materials for wastewater treatment

Special Issue Information

Dear Colleagues,

The aim of the Special Issue is to establish sustainable advanced materials to address the water, atmospheric pollution and energy issues. As described in the Sustainable Development Goals (SDG6), sustainable water and sanitation are becoming increasingly more important in society, and atmospheric CO₂ emission, which causes climate change, global warming, and rising sea levels, represents another important issue. As per the Paris agreement, the global warming rate must be kept under 2 °C or lower than that related to pre-industrial level. It is thus urgent to develop innovative advanced materials with broad energy and environmental applications.

This Special Issue covers durable innovative inorganic materials, organic materials, organic/inorganic hybrid materials and advanced functional materials for sustainable water, environmental remediation, solar utilization, and conversion into solar fuels. Papers on electrocatalytic water splitting, CO₂ reduction and fuels, and photo(electro)catalytic solar fuels are also welcome.

Dr. Karthikeyan Sekar
Dr. Boopathy Ramasamy
Guest Editors

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Keywords

solar light
water depollution
photo(electro)catalytic H2 production
photo(electro)catalytic solar fuel production

Published Papers (11 papers)

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Editorial

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3 pages, 174 KiB

Open AccessEditorial

Editorial: Special Issue on Advanced Functional Materials for Photo/Electro-Catalysts for Environmental and Energy Applications

by Boopathy Ramasamy and Karthikeyan Sekar

Catalysts 2023, 13(8), 1208; https://doi.org/10.3390/catal13081208 - 13 Aug 2023

Viewed by 797

Abstract

In the last three decades, it has become clearly evident that a sustainable approach to environmental issues and non-fossil energy production is impossible without functional materials [...] Full article

(This article belongs to the Special Issue Advanced Functional Materials for Photo/Electro-Catalysts for Environmental and Energy Applications)

Research

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15 pages, 4899 KiB

Open AccessArticle

Mixed-Phase Fe₂O₃ Derived from Natural Hematite Ores/C₃N₄ Z-Scheme Photocatalyst for Ofloxacin Removal

by Sulakshana Shenoy, Mohsen M. Farahat, Chitiphon Chuaicham, Karthikeyan Sekar, Boopathy Ramasamy and Keiko Sasaki

Catalysts 2023, 13(5), 792; https://doi.org/10.3390/catal13050792 - 23 Apr 2023

Cited by 4 | Viewed by 1789

Abstract

Abatement of pharmaceutical pollutants from aquatic systems is crucial but remains a challenge. Semiconductor photocatalysis has emerged as an eco-friendly technique that utilizes renewable solar energy to address environmental issues. Naturally occurring and earth abundant hematite (Fe₂O₃) ores can be incorporated as a suitable component of a photocatalyst. Herein, Brazilian hematite was partially phase transformed into heterophase (consisting of α/γ-Fe₂O₃) by a simple single-stage heat treatment procedure. The method of synthesis was simple and economical, requiring neither solvents nor concentrated acids. The existence of α/γ-phases in the produced Fe₂O₃ (FO) was confirmed by X-ray diffraction analysis. After the phase transformation process, the local structure surrounding the Fe atoms was varied as evidenced from X-ray absorption spectroscopy. Given its low toxicity, narrow bandgap, and chemical stability, FO was further combined with g-C₃N₄ (CN) to form composites. The optical properties of the synthesized CNFO composites confirmed that the visible light harvesting ability of CN was enhanced after combining with FO. The CN sheets were grown uniformly over the surface of FO as evidenced from scanning electron microscopy. The prepared composites could degrade an aqueous solution of ofloxacin (OFX, 10 ppm) under visible light with remarkable efficacy. The performance of CNFO-5% was 4.8 times higher when compared to pure CN. The initial rate constant value for the photocatalytic degradation of OFX by CNFO-5% was 0.1271 min⁻¹. The catalyst was stable even after five repeated cycles of photodegradation. The photoluminescence spectra and electrochemical measurements confirmed the efficient separation and transfer of the photogenerated charges across their interface. The investigations on different scavengers demonstrated that superoxide anion radicals and holes played a significant role in the degradation of OFX. The mechanism for the charge transfer was proposed to be a Z-scheme heterojunction. These results point to the potential of using inexpensive, abundant, and recyclable natural hematite ores as state-of-the-art photocatalysts for the elimination of pharmaceuticals in wastewater. Full article

(This article belongs to the Special Issue Advanced Functional Materials for Photo/Electro-Catalysts for Environmental and Energy Applications)

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17 pages, 6933 KiB

Open AccessArticle

Functionalized Graphene-Incorporated Cupric Oxide Charge-Transport Layer for Enhanced Photoelectrochemical Performance and Hydrogen Evolution

by Ambati Mounika Sai Krishna, Brindha Ramasubramanian, Sheik Haseena, Priyanka Bamola, Himani Sharma, Chandreswar Mahata, Alexander Chroneos, Satheesh Krishnamurthy, Mahesh Kumar Ravva, Basavaiah Chandu, Yee-Fun Lim, Avishek Kumar, Seeram Ramakrishna, Sajal Biring, Sabyasachi Chakrabortty and Goutam Kumar Dalapati

Catalysts 2023, 13(4), 785; https://doi.org/10.3390/catal13040785 - 21 Apr 2023

Cited by 4 | Viewed by 1990

Abstract

The production of hydrogen (H₂) through photoelectrochemical water splitting (PEC-WS) using renewable energy sources, particularly solar light, has been considered a promising solution for global energy and environmental challenges. In the field of hydrogen-scarce regions, metal oxide semiconductors have been extensively researched as photocathodes. For UV-visible light-driven PEC-WS, cupric oxide (CuO) has emerged as a suitable photocathode. However, the stability of the photocathode (CuO) against photo-corrosion is crucial in developing CuO-based PEC cells. This study reports a stable and effective CuO and graphene-incorporated (Gra-COOH) CuO nanocomposite photocathode through a sol-gel solution-based technique via spin coating. Incorporating graphene into the CuO nanocomposite photocathode resulted in higher stability and an increase in photocurrent compared to bare CuO photocathode electrodes. Compared to cuprous oxide (Cu₂O), the CuO photocathode was more identical and thermally stable during PEC-WS due to its high oxidation number. Additionally, the CuO:Gra-COOH nanocomposite photocathode exhibited a H₂ evolution of approximately 9.3 µmol, indicating its potential as a stable and effective photocathode for PEC-WS. The enhanced electrical properties of the CuO:Gra-COOH nanocomposite exemplify its potential for use as a charge-transport layer. Full article

(This article belongs to the Special Issue Advanced Functional Materials for Photo/Electro-Catalysts for Environmental and Energy Applications)

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19 pages, 6544 KiB

Open AccessArticle

Highly Effectual Photocatalytic Remediation of Tetracycline under the Broad Spectrum of Sunlight by Novel BiVO₄/Sb₂S₃ Nanocomposite

by Shelly Singla, Pooja Devi and Soumen Basu

Catalysts 2023, 13(4), 731; https://doi.org/10.3390/catal13040731 - 12 Apr 2023

Cited by 9 | Viewed by 1519

Abstract

Heterojunction photocatalysts (PC) with controllable compositions and in-built electric fields have attracted extensive research interest for their use in the remediation of environmental pollutants, owing to their supreme photocatalytic activity. Here, a simple hydrothermal route synthesizing different mole ratios of BiVO₄/Sb₂S₃ is reported as the PC. The inclusion of Sb₂S₃ with BiVO₄ in the BiVO₄/Sb₂S₃ composite possesses the ability to harvest a wide spectrum of solar light, an increased surface area, and an effective charge separation of the charge carriers. The efficacy of the synthesized catalyst was gauged by the photocatalytic abatement of a recalcitrant pollutant, tetracycline. The highest decomposition efficacy of 88.7% (rate constant 0.01557 min⁻¹) was achieved with 0.3 g/L of 1:3 BiVO₄:Sb₂S₃ photocatalyst for the tetracycline under sunlight illumination for 120 min. The catalyst was found stable for up to five cycles with a significant retention of its efficacy. The post-degradation characterizations revealed that the photocatalyst is stable due to the intactness of its crystalline planes, morphology, and surface area. Further, gas chromatography–mass spectrometry (GC–MS) was performed to study the decomposed products formed by the abatement of tetracycline. Moreover, chemical oxygen demand/ total organic carbon (COD/TOC) removals of 80.9% and 85.4%, respectively, were observed for the tetracycline standards, while for real TC pills, it was found to be 78.3% and 82.1%, respectively. This signifies that the photocatalyst has good surface catalytic properties in comparison to the existing expensive and time-consuming physicochemical approaches used in industry. Full article

(This article belongs to the Special Issue Advanced Functional Materials for Photo/Electro-Catalysts for Environmental and Energy Applications)

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14 pages, 4852 KiB

Open AccessArticle

Biowaste-Derived Heteroatom-Doped Porous Carbon as a Sustainable Electrocatalyst for Hydrogen Evolution Reaction

by Raji Atchudan, Suguna Perumal, Thomas Nesakumar Jebakumar Immanuel Edison, Ashok K. Sundramoorthy, Namachivayam Karthik, Sambasivam Sangaraju, Seung Tae Choi and Yong Rok Lee

Catalysts 2023, 13(3), 542; https://doi.org/10.3390/catal13030542 - 8 Mar 2023

Cited by 9 | Viewed by 1662

Abstract

Heteroatom-doped porous carbon material (H-PCM) was synthesized using Anacardium occidentale (cashew) nut’s skin by a simple pyrolysis route. The resulting H-PCM was thoroughly characterized by various analytical techniques such as field emission scanning electron microscopy (FE-SEM) with energy-dispersive X-ray (EDX) spectroscopy, high-resolution transmittance electron microscopy (HRTEM), X-ray diffraction (XRD), Raman spectroscopy, nitrogen adsorption–desorption isotherms, X-ray photoelectron spectroscopy (XPS), and attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectroscopy. The obtained results strongly demonstrated that the synthesized H-PCM exhibited a porous nature, continuous sponge-like and sheet-like smooth morphology, and a moderate degree of graphitization/crystallinity with oxygen-, nitrogen-, and sulfur-containing functionalities in the carbon matrix. After the structural confirmation, as-prepared H-PCM has used a sustainable electrocatalyst for hydrogen evolution reaction (HER) because the metal-free carbonaceous catalysts are one of the most promising candidates. The H-PCM showed excellent HER activities with a lowest Tafel slope of 75 mV dec⁻¹ and durable stability in 0.5 M H₂SO₄ aqueous solution. Moreover, this work provides a versatile and effective strategy for designing excellent metal-free electrocatalysts from the cheapest biowaste/biomass for large-scale production of hydrogen gas through electrochemical water splitting. Full article

(This article belongs to the Special Issue Advanced Functional Materials for Photo/Electro-Catalysts for Environmental and Energy Applications)

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15 pages, 4713 KiB

Open AccessArticle

Fabrication of Reduced Ag Nanoparticle Using Crude Extract of Cinnamon Decorated on ZnO as a Photocatalyst for Hexavalent Chromium Reduction

by Intan Nurul Rizki, Takumi Inoue, Chitiphon Chuaicham, Sulakshana Shenoy, Assadawoot Srikhaow, Karthikeyan Sekar and Keiko Sasaki

Catalysts 2023, 13(2), 265; https://doi.org/10.3390/catal13020265 - 24 Jan 2023

Cited by 4 | Viewed by 1656

Abstract

The crude extract of cinnamon (after abbreviated as KM) was used to produce silver nanoparticles (AgKM). This was subsequently utilized for the hydrothermal production of a composite consisting of AgKM decorated on zinc oxide (AgKM/ZnO) as a photocatalyst for reducing hexavalent chromium (Cr(VI)). Several methods e.g., XRD, SEM, TEM, XPS, PL, and RDB-PAS were used to analyze the optical and physicochemical properties of ZnO/AgKM samples in order to better comprehend the impact of the development of the AgKM-ZnO heterojunction in comparison to pure ZnO. In 60 min, the optimized ZnO/AgKM reduced Cr(VI) by more than 98%, with a rate constant 63 times faster than that of pure ZnO. The enhancement of the separation and transportation of photogenerated electron-hole pairs, as proven by a decrease in photoluminescence intensity when compared with ZnO, was attributed to the composite’s higher Cr(VI) reduction rate. Also, the formation of a new electronic level was created when AgKM are loaded on the surface of ZnO in the composites, as shown by the energy-resolved distribution of the electron trap (ERDT) pattern resulting to enhancement of light absorption ability by narrowing the energy band gap. Thus, ZnO/AgKM composite’s photocatalytic efficacy was enhanced by its narrow energy band gap and reduced charge recombination. Therefore, the newly produced ZnO/AgKM composite can be used as a photocatalyst to purify Cr(VI)-containing wastewater. Full article

(This article belongs to the Special Issue Advanced Functional Materials for Photo/Electro-Catalysts for Environmental and Energy Applications)

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12 pages, 2564 KiB

Open AccessArticle

Green-Routed Carbon Dot-Adorned Silver Nanoparticles for the Catalytic Degradation of Organic Dyes

by Suguna Perumal, Thomas Nesakumar Jebakumar Immanuel Edison, Raji Atchudan, Ashok K. Sundramoorthy and Yong Rok Lee

Catalysts 2022, 12(9), 937; https://doi.org/10.3390/catal12090937 - 24 Aug 2022

Cited by 12 | Viewed by 1895

Abstract

Herein, a simple, cost-effective, and in-situ environmentally friendly approach was adopted to synthesize carbon dot-adorned silver nanoparticles (CDs@AgNPs) from yellow myrobalan (Terminalia chebula) fruit using a hydrothermal treatment without any additional reducing and or stabilizing agents. The as-synthesized CDs@AgNP composite was systematically characterized using multiple analytical techniques: FESEM, TEM, XRD, Raman, ATR-FTIR, XPS, and UV-vis spectroscopy. All the results of the characterization techniques strongly support the idea that the CDs were successfully made to adorn the AgNPs. This effectively synthesized CDs@AgNP composite was applied as a catalyst for the degradation of organic dyes, including methylene blue (MB) and methyl orange (MO). The degradation results revealed that CDs@AgNPs exhibit a superior catalytic activity in the degradation of MB and MO in the presence of NaBH₄ (SB) under ambient temperatures. In total, 99.5 and 99.0% rates of degradation of MB and MO were observed using CDs@AgNP composite with SB, respectively. A plausible mechanism for the reductive degradation of MB and MO is discussed in detail. Moreover, the CDs@AgNP composite has great potential for wastewater treatment applications. Full article

(This article belongs to the Special Issue Advanced Functional Materials for Photo/Electro-Catalysts for Environmental and Energy Applications)

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13 pages, 4235 KiB

Open AccessArticle

Synthesis, Characterizations and Catalysis of Sulfated Silica and Nickel Modified Silica Catalysts for Diethyl Ether (DEE) Production from Ethanol towards Renewable Energy Applications

by Karna Wijaya, Melynatri Laura Lammaduma Malau, Maisari Utami, Sri Mulijani, Aep Patah, Arief Cahyo Wibowo, Murugesan Chandrasekaran, Jothi Ramalingam Rajabathar and Hamad A. Al-Lohedan

Catalysts 2021, 11(12), 1511; https://doi.org/10.3390/catal11121511 - 11 Dec 2021

Cited by 18 | Viewed by 3087

Abstract

Sulfated silica (SO₄/SiO₂) and nickel impregnated sulfated silica (Ni-SO₄/SiO₂) catalysts have been successfully carried out for the conversion of ethanol into diethyl ether (DEE) as a biofuel. The aims of this research were to study the effects of acidity on the SO₄/SiO₂ and Ni-SO₄/SiO₂ catalysts in the conversion of ethanol into diethyl ether. This study focuses on the increases in activity and selectivity of SiO₂ with the impregnation of sulfate and Ni metal, which had good activity and acidity and were less expensive. The SO₄/SiO₂ catalysts were prepared using TEOS (Tetraethyl Orthosilicate) as a precursor and sulfuric acid with various concentrations (1, 2, 3, 4 M). The results showed that SO₄/SiO₂ acid catalyst treated with 2 M H₂SO₄ and calcined at 400 °C (SS-2-400) was the catalyst with highest total acidity (2.87 g/mmol), while the impregnation of Ni metal showed the highest acidity value at 3%/Ni-SS-2 catalyst (4.89 g/mmol). The SS-2-400 and 3%/Ni-SS-2 catalysts were selected and applied in the ethanol dehydration process into diethyl ether at temperatures 175, 200, and 225 °C. The activity and selectivity of SS-2-400 and 3%/Ni-SS-2 catalysts shown the conversion of ethanol reached up to 9.54% with good selectivity towards diethyl ether liquid product formation. Full article

(This article belongs to the Special Issue Advanced Functional Materials for Photo/Electro-Catalysts for Environmental and Energy Applications)

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Review

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30 pages, 4982 KiB

Open AccessEditor’s ChoiceReview

Recent Advances on Small Band Gap Semiconductor Materials (≤2.1 eV) for Solar Water Splitting

by Hefeng Zhang, Jiaqi Liu, Ting Xu, Wenqian Ji and Xu Zong

Catalysts 2023, 13(4), 728; https://doi.org/10.3390/catal13040728 - 12 Apr 2023

Cited by 18 | Viewed by 6099

Abstract

The conversion of solar energy into renewable H₂ fuel via photoelectrochemical and photocatalytic water splitting approaches has attracted considerable attention due to its potential to solve significant energy and environmental issues. To achieve reasonable energy conversion efficiency of 10%, which is amenable to the economic feasibility of this technology, semiconductor materials, which are the main carrier for solar H₂ production, must fulfill several important criteria. One of the most important criteria is the band gap of the semiconductor material, which should be low enough to allow the efficient absorption of incident light. This is because the band gap of semiconductor material fundamentally determines the upper limit of the theoretical energy conversion efficiency of the solar conversion system. In this work, recent advances in utilizing semiconductor material with a band gap smaller than 2.1 eV instead of the simply-defined visible-light-responsive semiconductor materials toward solar H₂ production from water splitting was reviewed. Full article

(This article belongs to the Special Issue Advanced Functional Materials for Photo/Electro-Catalysts for Environmental and Energy Applications)

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26 pages, 5491 KiB

Open AccessReview

Recent Advances in Perovskite Catalysts for Efficient Overall Water Splitting

by Conghui Si, Wenchao Zhang, Qifang Lu, Enyan Guo, Zhou Yang, Jiyun Chen, Xinya He and Jing Luo

Catalysts 2022, 12(6), 601; https://doi.org/10.3390/catal12060601 - 31 May 2022

Cited by 21 | Viewed by 5101

Abstract

Hydrogen is considered a promising clean energy vector with the features of high energy capacity and zero-carbon emission. Water splitting is an environment-friendly and effective route for producing high-purity hydrogen, which contains two important half-cell reactions, namely, the anodic oxygen evolution reaction (OER) and the cathodic hydrogen evolution reaction (HER). At the heart of water splitting is high-performance electrocatalysts that efficiently improve the rate and selectivity of key chemical reactions. Recently, perovskite oxides have emerged as promising candidates for efficient water splitting electrocatalysts owing to their low cost, high electrochemical stability, and compositional and structural flexibility allowing for the achievement of high intrinsic electrocatalytic activity. In this review, we summarize the present research progress in the design, development, and application of perovskite oxides for electrocatalytic water splitting. The emphasis is on the innovative synthesis strategies and a deeper understanding of structure–activity relationships through a combination of systematic characterization and theoretical research. Finally, the main challenges and prospects for the further development of more efficient electrocatalysts based on perovskite oxides are proposed. It is expected to give guidance for the development of novel non-noble metal catalysts in electrochemical water splitting. Full article

(This article belongs to the Special Issue Advanced Functional Materials for Photo/Electro-Catalysts for Environmental and Energy Applications)

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28 pages, 15945 KiB

Open AccessReview

A Critical Study of Cu₂O: Synthesis and Its Application in CO₂ Reduction by Photochemical and Electrochemical Approaches

by Sathya Mohan, Brahmari Honnappa, Ashil Augustin, Mariyappan Shanmugam, Chitiphon Chuaicham, Keiko Sasaki, Boopathy Ramasamy and Karthikeyan Sekar

Catalysts 2022, 12(4), 445; https://doi.org/10.3390/catal12040445 - 17 Apr 2022

Cited by 12 | Viewed by 8264

Abstract

Copper oxide (Cu₂O) is a potential material as a catalyst for CO₂ reduction. Cu₂O nanostructures have many advantages, including interfacial charge separation and transportation, enhanced surface area, quantum efficiency, and feasibility of modification via composite development or integration of the favorable surface functional groups. We cover the current advancements in the synthesis of Cu₂O nanomaterials in various morphological dimensions and their photochemical and electrochemical applications, which complies with the physical enrichment of their enhanced activity in every application they are employed in. The scope of fresh designs, namely composites or the hierarchy of copper oxide nanostructures, and various ways to improve CO₂ reduction performance are also discussed in this review. Photochemical and electrochemical CO₂ transformations have received tremendous attention in the last few years, thanks to the growing interest in renewable sources of energy and green facile chemistry. The current review provides an idea of current photochemical and electrochemical carbon dioxide fixing techniques by using Cu₂O-based materials. Carboxylation and carboxylative cyclization, yield valuable chemicals such as carboxylic acids and heterocyclic compounds. Radical ions, which are induced by photo- and electrochemical reactions, as well as other high-energy organic molecules, are regarded as essential mid-products in photochemical and electrochemical reactions with CO₂. It has also been claimed that CO₂ can be activated to form radical anions. Full article

(This article belongs to the Special Issue Advanced Functional Materials for Photo/Electro-Catalysts for Environmental and Energy Applications)

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