Review

46 pages, 6768 KiB

Open AccessReview

Copper Oxide-Based Photocatalysts and Photocathodes: Fundamentals and Recent Advances

by Tomasz Baran, Alberto Visibile, Michael Busch, Xiufang He, Szymon Wojtyla, Sandra Rondinini, Alessandro Minguzzi and Alberto Vertova

Molecules 2021, 26(23), 7271; https://0-doi-org.brum.beds.ac.uk/10.3390/molecules26237271 - 30 Nov 2021

Cited by 20 | Viewed by 4544

Abstract

This work aims at reviewing the most impactful results obtained on the development of Cu-based photocathodes. The need of a sustainable exploitation of renewable energy sources and the parallel request of reducing pollutant emissions in airborne streams and in waters call for new [...] Read more.

This work aims at reviewing the most impactful results obtained on the development of Cu-based photocathodes. The need of a sustainable exploitation of renewable energy sources and the parallel request of reducing pollutant emissions in airborne streams and in waters call for new technologies based on the use of efficient, abundant, low-toxicity and low-cost materials. Photoelectrochemical devices that adopts abundant element-based photoelectrodes might respond to these requests being an enabling technology for the direct use of sunlight to the production of energy fuels form water electrolysis (H₂) and CO₂ reduction (to alcohols, light hydrocarbons), as well as for the degradation of pollutants. This review analyses the physical chemical properties of Cu₂O (and CuO) and the possible strategies to tune them (doping, lattice strain). Combining Cu with other elements in multinary oxides or in composite photoelectrodes is also discussed in detail. Finally, a short overview on the possible applications of these materials is presented. Full article

(This article belongs to the Special Issue Feature Review Papers in Electrochemistry)

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26 pages, 2605 KiB

Open AccessFeature PaperReview

Electrochemical Technologies to Decrease the Chemical Risk of Hospital Wastewater and Urine

by Ángela Moratalla, Salvador Cotillas, Engracia Lacasa, Pablo Cañizares, Manuel A. Rodrigo and Cristina Sáez

Molecules 2021, 26(22), 6813; https://0-doi-org.brum.beds.ac.uk/10.3390/molecules26226813 - 11 Nov 2021

Cited by 12 | Viewed by 2275

Abstract

The inefficiency of conventional biological processes to remove pharmaceutical compounds (PhCs) in wastewater is leading to their accumulation in aquatic environments. These compounds are characterized by high toxicity, high antibiotic activity and low biodegradability, and their presence is causing serious environmental risks. Because [...] Read more.

The inefficiency of conventional biological processes to remove pharmaceutical compounds (PhCs) in wastewater is leading to their accumulation in aquatic environments. These compounds are characterized by high toxicity, high antibiotic activity and low biodegradability, and their presence is causing serious environmental risks. Because much of the PhCs consumed by humans are excreted in the urine, hospital effluents have been considered one of the main routes of entry of PhCs into the environment. In this work, a critical review of the technologies employed for the removal of PhCs in hospital wastewater was carried out. This review provides an overview of the current state of the developed technologies for decreasing the chemical risks associated with the presence of PhCs in hospital wastewater or urine in the last years, including conventional treatments (filtration, adsorption, or biological processes), advanced oxidation processes (AOPs) and electrochemical advanced oxidation processes (EAOPs). Full article

(This article belongs to the Special Issue Feature Review Papers in Electrochemistry)

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24 pages, 4128 KiB

Open AccessFeature PaperReview

Recent Advances in Alkaline Exchange Membrane Water Electrolysis and Electrode Manufacturing

by Ester López-Fernández, Celia Gómez Sacedón, Jorge Gil-Rostra, Francisco Yubero, Agustín R. González-Elipe and Antonio de Lucas-Consuegra

Molecules 2021, 26(21), 6326; https://0-doi-org.brum.beds.ac.uk/10.3390/molecules26216326 - 20 Oct 2021

Cited by 48 | Viewed by 10685

Abstract

Water electrolysis to obtain hydrogen in combination with intermittent renewable energy resources is an emerging sustainable alternative to fossil fuels. Among the available electrolyzer technologies, anion exchange membrane water electrolysis (AEMWE) has been paid much attention because of its advantageous behavior compared to [...] Read more.

Water electrolysis to obtain hydrogen in combination with intermittent renewable energy resources is an emerging sustainable alternative to fossil fuels. Among the available electrolyzer technologies, anion exchange membrane water electrolysis (AEMWE) has been paid much attention because of its advantageous behavior compared to other more traditional approaches such as solid oxide electrolyzer cells, and alkaline or proton exchange membrane water electrolyzers. Recently, very promising results have been obtained in the AEMWE technology. This review paper is focused on recent advances in membrane electrode assembly components, paying particular attention to the preparation methods for catalyst coated on gas diffusion layers, which has not been previously reported in the literature for this type of electrolyzers. The most successful methodologies utilized for the preparation of catalysts, including co-precipitation, electrodeposition, sol–gel, hydrothermal, chemical vapor deposition, atomic layer deposition, ion beam sputtering, and magnetron sputtering deposition techniques, have been detailed. Besides a description of these procedures, in this review, we also present a critical appraisal of the efficiency of the water electrolysis carried out with cells fitted with electrodes prepared with these procedures. Based on this analysis, a critical comparison of cell performance is carried out, and future prospects and expected developments of the AEMWE are discussed. Full article

(This article belongs to the Special Issue Feature Review Papers in Electrochemistry)

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27 pages, 5945 KiB

Open AccessReview

The Surge of Metal–Organic-Framework (MOFs)-Based Electrodes as Key Elements in Electrochemically Driven Processes for the Environment

by Abdoulaye Thiam, Juan A. Lopez-Ruiz, Dushyant Barpaga and Sergi Garcia-Segura

Molecules 2021, 26(18), 5713; https://0-doi-org.brum.beds.ac.uk/10.3390/molecules26185713 - 21 Sep 2021

Cited by 12 | Viewed by 4089

Abstract

Metal–organic-frameworks (MOFs) are emerging materials used in the environmental electrochemistry community for Faradaic and non-Faradaic water remediation technologies. It has been concluded that MOF-based materials show improvement in performance compared to traditional (non-)faradaic materials. In particular, this review outlines MOF synthesis and their [...] Read more.

Metal–organic-frameworks (MOFs) are emerging materials used in the environmental electrochemistry community for Faradaic and non-Faradaic water remediation technologies. It has been concluded that MOF-based materials show improvement in performance compared to traditional (non-)faradaic materials. In particular, this review outlines MOF synthesis and their application in the fields of electron- and photoelectron-Fenton degradation reactions, photoelectrocatalytic degradations, and capacitive deionization physical separations. This work overviews the main electrode materials used for the different environmental remediation processes, discusses the main performance enhancements achieved via the utilization of MOFs compared to traditional materials, and provides perspective and insights for the further development of the utilization of MOF-derived materials in electrified water treatment. Full article

(This article belongs to the Special Issue Feature Review Papers in Electrochemistry)

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25 pages, 1228 KiB

Open AccessReview

An Old Technique with A Promising Future: Recent Advances in the Use of Electrodeposition for Metal Recovery

by Yelitza Delgado, Francisco J. Fernández-Morales and Javier Llanos

Molecules 2021, 26(18), 5525; https://0-doi-org.brum.beds.ac.uk/10.3390/molecules26185525 - 11 Sep 2021

Cited by 5 | Viewed by 2329

Abstract

Although the first published works on electrodeposition dates from more than one century ago (1905), the uses of this technique in the recovery of metals are attracting an increasing interest from the scientific community in the recent years. Moreover, the intense use of [...] Read more.

Although the first published works on electrodeposition dates from more than one century ago (1905), the uses of this technique in the recovery of metals are attracting an increasing interest from the scientific community in the recent years. Moreover, the intense use of metals in electronics and the necessity to assure a second life of these devices in a context of circular economy, have increased the interest of the scientific community on electrodeposition, with almost 3000 works published per year nowadays. In this review, we aim to revise the most relevant and recent publications in the application of electrodeposition for metal recovery. These contributions have been classified into four main groups of approaches: (1) treatment and reuse of wastewater; (2) use of ionic liquids; (3) use of bio-electrochemical processes (microbial fuel cells and microbial electrolysis cells) and (4) integration of electrodeposition with other processes (bioleaching, adsorption, membrane processes, etc.). This would increase the awareness about the importance of the technology and would serve as a starting point for anyone that aims to start working in the field. Full article

(This article belongs to the Special Issue Feature Review Papers in Electrochemistry)

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28 pages, 864 KiB

Open AccessReview

Electro-Persulfate Processes for the Treatment of Complex Wastewater Matrices: Present and Future

by Annabel Fernandes, Maria João Nunes, Ana Sofia Rodrigues, Maria José Pacheco, Lurdes Ciríaco and Ana Lopes

Molecules 2021, 26(16), 4821; https://0-doi-org.brum.beds.ac.uk/10.3390/molecules26164821 - 09 Aug 2021

Cited by 35 | Viewed by 3269

Abstract

Complex wastewater matrices present a major environmental concern. Besides the biodegradable organics, they may contain a great variety of toxic chemicals, heavy metals, and other xenobiotics. The electrochemically activated persulfate process, an efficient way to generate sulfate radicals, has been widely applied to [...] Read more.

Complex wastewater matrices present a major environmental concern. Besides the biodegradable organics, they may contain a great variety of toxic chemicals, heavy metals, and other xenobiotics. The electrochemically activated persulfate process, an efficient way to generate sulfate radicals, has been widely applied to the degradation of such complex effluents with very good results. This review presents the fundamentals of the electro-persulfate processes, highlighting the advantages and limitations, followed by an exhaustive evaluation on the application of this process for the treatment of complex industrial effluents. An overview of the main relevant experimental parameters/details and their influence on the organic load removal is presented and discussed, having in mind the application of these technologies at an industrial scale. Finally, the future perspectives for the application of the electro-persulfate processes in the treatment of complex wastewater matrices is outlined. Full article

(This article belongs to the Special Issue Feature Review Papers in Electrochemistry)

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39 pages, 3159 KiB

Open AccessReview

Benchmarking Catalysts for Formic Acid/Formate Electrooxidation

by Scott J. Folkman, Jesús González-Cobos, Stefano Giancola, Irene Sánchez-Molina and José Ramón Galán-Mascarós

Molecules 2021, 26(16), 4756; https://0-doi-org.brum.beds.ac.uk/10.3390/molecules26164756 - 06 Aug 2021

Cited by 8 | Viewed by 4613

Abstract

Energy production and consumption without the use of fossil fuels are amongst the biggest challenges currently facing humankind and the scientific community. Huge efforts have been invested in creating technologies that enable closed carbon or carbon neutral fuel cycles, limiting CO₂ emissions [...] Read more.

Energy production and consumption without the use of fossil fuels are amongst the biggest challenges currently facing humankind and the scientific community. Huge efforts have been invested in creating technologies that enable closed carbon or carbon neutral fuel cycles, limiting CO₂ emissions into the atmosphere. Formic acid/formate (FA) has attracted intense interest as a liquid fuel over the last half century, giving rise to a plethora of studies on catalysts for its efficient electrocatalytic oxidation for usage in fuel cells. However, new catalysts and catalytic systems are often difficult to compare because of the variability in conditions and catalyst parameters examined. In this review, we discuss the extensive literature on FA electrooxidation using platinum, palladium and non-platinum group metal-based catalysts, the conditions typically employed in formate electrooxidation and the main electrochemical parameters for the comparison of anodic electrocatalysts to be applied in a FA fuel cell. We focused on the electrocatalytic performance in terms of onset potential and peak current density obtained during cyclic voltammetry measurements and on catalyst stability. Moreover, we handpicked a list of the most relevant examples that can be used for benchmarking and referencing future developments in the field. Full article

(This article belongs to the Special Issue Feature Review Papers in Electrochemistry)

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37 pages, 12268 KiB

Open AccessReview

Effect of Anode Material on Electrochemical Oxidation of Low Molecular Weight Alcohols—A Review

by Marta Wala and Wojciech Simka

Molecules 2021, 26(8), 2144; https://0-doi-org.brum.beds.ac.uk/10.3390/molecules26082144 - 09 Apr 2021

Cited by 37 | Viewed by 4080

Abstract

The growing climate crisis inspires one of the greatest challenges of the 21st century—developing novel power sources. One of the concepts that offer clean, non-fossil electricity production is fuel cells, especially when the role of fuel is played by simple organic molecules, such [...] Read more.

The growing climate crisis inspires one of the greatest challenges of the 21st century—developing novel power sources. One of the concepts that offer clean, non-fossil electricity production is fuel cells, especially when the role of fuel is played by simple organic molecules, such as low molecular weight alcohols. The greatest drawback of this technology is the lack of electrocatalytic materials that would enhance reaction kinetics and good stability under process conditions. Currently, electrodes for direct alcohol fuel cells (DAFCs) are mainly based on platinum, which not only provides a poor reaction rate but also readily deactivates because of poisoning by reaction products. Because of these disadvantages, many researchers have focused on developing novel electrode materials with electrocatalytic properties towards the oxidation of simple alcohols, such as methanol, ethanol, ethylene glycol or propanol. This paper presents the development of electrode materials and addresses future challenges that still need to be overcome before direct alcohol fuel cells can be commercialized. Full article

(This article belongs to the Special Issue Feature Review Papers in Electrochemistry)

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