Editorial

2 pages, 154 KiB

Open AccessEditorial

Immobilized Non-Precious Electrocatalysts for Advanced Energy Devices

by Nasser A. M. Barakat

Catalysts 2022, 12(6), 607; https://doi.org/10.3390/catal12060607 - 02 Jun 2022

Viewed by 982

The expected near depletion of fossil fuels encourages both the research and industrial communities to focus their efforts to find effective and sustainable alternatives [...] Full article

(This article belongs to the Special Issue Immobilized Non-Precious Electrocatalysts for Advanced Energy Devices)

Research

Jump to: Editorial, Review

14 pages, 1527 KiB

Open AccessArticle

Comparison of Direct and Mediated Electron Transfer for Bilirubin Oxidase from Myrothecium Verrucaria. Effects of Inhibitors and Temperature on the Oxygen Reduction Reaction

by Riccarda Antiochia, Diego Oyarzun, Julio Sánchez and Federico Tasca

Catalysts 2019, 9(12), 1056; https://doi.org/10.3390/catal9121056 - 11 Dec 2019

Cited by 14 | Viewed by 3607

Abstract

One of the processes most studied in bioenergetic systems in recent years is the oxygen reduction reaction (ORR). An important challenge in bioelectrochemistry is to achieve this reaction under physiological conditions. In this study, we used bilirubin oxidase (BOD) from Myrothecium verrucaria, [...] Read more.

One of the processes most studied in bioenergetic systems in recent years is the oxygen reduction reaction (ORR). An important challenge in bioelectrochemistry is to achieve this reaction under physiological conditions. In this study, we used bilirubin oxidase (BOD) from Myrothecium verrucaria, a subclass of multicopper oxidases (MCOs), to catalyse the ORR to water via four electrons in physiological conditions. The active site of BOD, the T2/T3 cluster, contains three Cu atoms classified as T2, T3α, and T3β depending on their spectroscopic characteristics. A fourth Cu atom; the T1 cluster acts as a relay of electrons to the T2/T3 cluster. Graphite electrodes were modified with BOD and the direct electron transfer (DET) to the enzyme, and the mediated electron transfer (MET) using an osmium polymer (OsP) as a redox mediator, were compared. As a result, an alternative resting (AR) form was observed in the catalytic cycle of BOD. In the absence and presence of the redox mediator, the AR direct reduction occurs through the trinuclear site (TNC) via T1, specifically activated at low potentials in which T2 and T3α of the TNC are reduced and T3β is oxidized. A comparative study between the DET and MET was conducted at various pH and temperatures, considering the influence of inhibitors like H₂O₂, F⁻, and Cl⁻. In the presence of H₂O₂ and F⁻, these bind to the TNC in a non-competitive reversible inhibition of O₂. Instead; Cl⁻ acts as a competitive inhibitor for the electron donor substrate and binds to the T1 site. Full article

(This article belongs to the Special Issue Immobilized Non-Precious Electrocatalysts for Advanced Energy Devices)

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12 pages, 39834 KiB

Open AccessArticle

Electrochemical Oxidation of Urea on NiCu Alloy Nanoparticles Decorated Carbon Nanofibers

by Ahmed Abutaleb

Catalysts 2019, 9(5), 397; https://doi.org/10.3390/catal9050397 - 28 Apr 2019

Cited by 29 | Viewed by 6001

Abstract

Bimetallic Cu_3.8Ni alloy nanoparticles (NPs)-anchored carbon nanofibers (composite NFs) were synthesized using a simple electrospinning machine. XRD, SEM, TEM, and TGA were employed to examine the physiochemical characteristics of these composite NFs. The characterization techniques proved that Cu_3.8Ni alloy [...] Read more.

Bimetallic Cu_3.8Ni alloy nanoparticles (NPs)-anchored carbon nanofibers (composite NFs) were synthesized using a simple electrospinning machine. XRD, SEM, TEM, and TGA were employed to examine the physiochemical characteristics of these composite NFs. The characterization techniques proved that Cu_3.8Ni alloy NPs-anchored carbon NFs were successfully fabricated. Urea oxidation (UO) processes as a source of hydrogen and electrical energy were investigated using the fabricated composite NFs. The corresponding onset potential of UO and the oxidation current density (OCD) were measured via cyclic voltammetry as 380 mV versus Ag/AgCl electrode and 98 mA/cm², respectively. Kinetic study indicated that the electrochemical oxidation of urea followed the diffusion controlled process and the reaction order is 0.5 with respect to urea concentration. The diffusion coefficient of urea using the introduced electrocatalyst was found to be 6.04 × 10⁻³ cm²/s. Additionally, the composite NFs showed steady state stability for 900 s using chronoamperometry test. Full article

(This article belongs to the Special Issue Immobilized Non-Precious Electrocatalysts for Advanced Energy Devices)

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17 pages, 8762 KiB

Open AccessArticle

Influence of Sn Content, Nanostructural Morphology, and Synthesis Temperature on the Electrochemical Active Area of Ni-Sn/C Nanocomposite: Verification of Methanol and Urea Electrooxidation

by Nasser A. M. Barakat, Mohammad Ali Abdelkareem and Emad A. M. Abdelghani

Catalysts 2019, 9(4), 330; https://doi.org/10.3390/catal9040330 - 03 Apr 2019

Cited by 22 | Viewed by 4082

Abstract

In contrast to precious metals (e.g., Pt), which possess their electro catalytic activities due to their surface electronic structure, the activity of the Ni-based electrocatalysts depends on formation of an electroactive surface area (ESA) from the oxyhydroxide layer (NiOOH). In this study, the [...] Read more.

In contrast to precious metals (e.g., Pt), which possess their electro catalytic activities due to their surface electronic structure, the activity of the Ni-based electrocatalysts depends on formation of an electroactive surface area (ESA) from the oxyhydroxide layer (NiOOH). In this study, the influences of Sn content, nanostructural morphology, and synthesis temperature on the ESA of Sn-incorporated Ni/C nanostructures were studied. To investigate the effect of the nanostructural, Sn-incorporated Ni/C nanostructures, nanofibers were synthesized by electrospinning a tin chloride/nickel acetate/poly (vinyl alcohol) solution, followed by calcination under inert atmosphere at high temperatures (700, 850, and 1000 °C). On the other hand, the same composite was formulated in nanoparticulate form by a sol-gel procedure. The electrochemical measurements indicated that the nanofibrous morphology strongly enhanced formation of the ESA. Investigation of the tin content concluded that the optimum co-catalyst content depends on the synthesis temperature. Typically, the maximum ESA was observed at 10 and 15 wt % of the co-catalyst for the nanofibers prepared at 700 and 850 °C, respectively. Study of the effect of synthesis temperature concluded that at the same tin content, 850 °C calcination temperature reveals the best activity compared to 700 and 1000 °C. Practical verification was achieved by investigation of the electrocatalytic activity toward methanol and urea oxidation. The results confirmed that the activity is directly proportionate to the ESA, especially in the case of urea oxidation. Moreover, beside the distinct increase in the current density, at the optimum calcination temperature and co-catalyst content, a distinguished decrease in the onset potential of both urea and methanol oxidation was observed. Full article

(This article belongs to the Special Issue Immobilized Non-Precious Electrocatalysts for Advanced Energy Devices)

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13 pages, 2892 KiB

Open AccessArticle

One Simple Strategy towards Nitrogen and Oxygen Codoped Carbon Nanotube for Efficient Electrocatalytic Oxygen Reduction and Evolution

by Jing Sun, Shujin Wang, Yinghua Wang, Haibo Li, Huawei Zhou, Baoli Chen, Xianxi Zhang, Hongyan Chen, Konggang Qu and Jinsheng Zhao

Catalysts 2019, 9(2), 159; https://doi.org/10.3390/catal9020159 - 06 Feb 2019

Cited by 10 | Viewed by 3507

Abstract

The development of advanced electrocatalysts for oxygen reduction and evolution is of paramount significance to fuel cells, water splitting, and metal-air batteries. Heteroatom-doped carbon materials have exhibited great promise because of their excellent electrical conductivity, abundance, and superior durability. Rationally optimizing active sites [...] Read more.

The development of advanced electrocatalysts for oxygen reduction and evolution is of paramount significance to fuel cells, water splitting, and metal-air batteries. Heteroatom-doped carbon materials have exhibited great promise because of their excellent electrical conductivity, abundance, and superior durability. Rationally optimizing active sites of doped carbons can remarkably enhance their electrocatalytic performance. In this study, nitrogen and oxygen codoped carbon nanotubes were readily synthesized from the pyrolysis of polydopamine-carbon nanotube hybrids. Different electron microscopes, Raman spectra and X-ray photoelectron spectroscopy (XPS) were employed to survey the morphological and componential properties. The newly-obtained catalyst features high-quality nitrogen and oxygen species, favourable porous structures and excellent electric conductivity, and thus exhibits remarkably bifunctional oxygen electrode activity. This research further helps to advance the knowledge of polydopamine and its potential applications as efficient electrocatalysts to replace noble metals. Full article

(This article belongs to the Special Issue Immobilized Non-Precious Electrocatalysts for Advanced Energy Devices)

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10 pages, 1642 KiB

Open AccessArticle

Facile Synthesis and Characterization of Two Dimensional SnO₂-Decorated Graphene Oxide as an Effective Counter Electrode in the DSSC

by Mohamed S. Mahmoud, Moaaed Motlak and Nasser A. M. Barakat

Catalysts 2019, 9(2), 139; https://doi.org/10.3390/catal9020139 - 01 Feb 2019

Cited by 15 | Viewed by 3347

Abstract

SnO₂-decorated graphene oxide (SnO₂/GO) was synthesized by the modified Hummers’s method, followed by a chemical incorporation of SnO₂ nanoparticles. Then, the nanocomposite was used as anon-precious counter electrode in a dye-sensitized solar cell (DSSC). Although GO has a [...] Read more.

SnO₂-decorated graphene oxide (SnO₂/GO) was synthesized by the modified Hummers’s method, followed by a chemical incorporation of SnO₂ nanoparticles. Then, the nanocomposite was used as anon-precious counter electrode in a dye-sensitized solar cell (DSSC). Although GO has a relatively poor electrical conductivity depending essentially on the extent of the graphite oxidation, presence of SnO₂ enhanced its structural and electrochemical properties. The Pt-free counter electrode exhibited a distinct catalytic activity toward iodine reduction and a low resistance to electron transfer. Moreover, the decorated GO provided extra active sites for reducing I₃⁻ at the interface of the CE/electrolyte. In addition, the similarity of the dopant in the GO film and the fluorine-doped tin oxide (FTO) substrate promoted a strong assimilation between them. Therefore, SnO₂-decorated GO, as a counter electrode, revealed an enhanced photon to electron conversion efficiency of 4.57%. Consequently, the prepared SnO₂/GO can be sorted as an auspicious counter electrode for DSSCs. Full article

(This article belongs to the Special Issue Immobilized Non-Precious Electrocatalysts for Advanced Energy Devices)

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11 pages, 2989 KiB

Open AccessArticle

Ternary N, S, and P-Doped Hollow Carbon Spheres Derived from Polyphosphazene as Pd Supports for Ethanol Oxidation Reaction

by Ke Yu, Yan Lin, Jinchen Fan, Qiaoxia Li, Penghui Shi, Qunjie Xu and Yulin Min

Catalysts 2019, 9(2), 114; https://doi.org/10.3390/catal9020114 - 26 Jan 2019

Cited by 18 | Viewed by 3356

Abstract

Ethanol oxidation reaction (EOR) is an important electrode reaction in ethanol fuel cells. However, there are many problems with commercial ethanol oxidation electrocatalysts today, such as poor durability, poor anti-CO poisoning ability, and low selectivity for C–C bond cleavage. Therefore, it is very [...] Read more.

Ethanol oxidation reaction (EOR) is an important electrode reaction in ethanol fuel cells. However, there are many problems with commercial ethanol oxidation electrocatalysts today, such as poor durability, poor anti-CO poisoning ability, and low selectivity for C–C bond cleavage. Therefore, it is very meaningful to develop a high-performance EOR catalyst. Herein, we designed ternary N, S, and P-doped hollow carbon spheres (C–N,P,S) from polyphosphazene (PCCP) as Pd supports for EOR. Using SiO₂ spheres as the templates, the PCCP was first coated on the surfaces of SiO₂ spheres by in situ polymerization. Through high-temperature pyrolysis and hydrofluoric acid-etching, the hollow PCCP has a large surface area and porous structure. After loading Pd nanoparticles (NPs), the Pd/C–N, P, S catalysts with Pd NPs decorated on the surfaces of C–N, P, S can achieve a high mass peak current density of 1686 mA mg_Pd⁻¹, which was 2.8 times greater than that of Pd/C. Meanwhile, the Pd/C–N, P, S catalyst also shows a better stability than that of Pd/C after a durability test of 3600s. Full article

(This article belongs to the Special Issue Immobilized Non-Precious Electrocatalysts for Advanced Energy Devices)

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12 pages, 3846 KiB

Open AccessArticle

Metallosupramolecular Polymer Precursor Design for Multi-Element Co-Doped Carbon Shells with Improved Oxygen Reduction Reaction Catalytic Activity

by Yuzhe Wu, Yuntong Li, Jie Mao, Haiyang Wu, Tong Wu, Yaying Li, Birong Zeng, Yiting Xu, Conghui Yuan and Lizong Dai

Catalysts 2019, 9(1), 102; https://doi.org/10.3390/catal9010102 - 18 Jan 2019

Cited by 7 | Viewed by 4386

Abstract

Heteroatom-doped carbon materials have been extensively studied in the field of electrochemical catalysis to solve the challenges of energy shortage. In particular, there is vigorous research activity in the design of multi-element co-doped carbon materials for the improvement of electrochemical performance. Herein, we [...] Read more.

Heteroatom-doped carbon materials have been extensively studied in the field of electrochemical catalysis to solve the challenges of energy shortage. In particular, there is vigorous research activity in the design of multi-element co-doped carbon materials for the improvement of electrochemical performance. Herein, we developed a supramolecular approach to construct metallosupramolecular polymer hollow spheres, which could be used as precursors for the generation of carbon shells co-doped with B, N, F and Fe elements. The metallosupramolecular polymer hollow spheres were fabricated through a simple route based on the Kirkendall effect. The in situ reaction between the boronate polymer spheres and Fe³⁺ could easily control the component and shell thickness of the precursors. The as-prepared multi-element co-doped carbon shells showed excellent catalytic activity in an oxygen reduction reaction, with onset potential (E_onset) 0.91 V and half-wave (E_half-wave) 0.82 V vs reversible hydrogen electrode (RHE). The fluorine element in the carbon matrix was important for the improvement of oxygen reduction reaction (ORR) activity performance through designing the control experiment. This supramolecular approach may afford a new route to explore good activity and a low-cost catalyst for ORR. Full article

(This article belongs to the Special Issue Immobilized Non-Precious Electrocatalysts for Advanced Energy Devices)

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12 pages, 2679 KiB

Open AccessArticle

Electro-Reduction of Molecular Oxygen Mediated by a Cobalt(II)octaethylporphyrin System onto Oxidized Glassy Carbon/Oxidized Graphene Substrate

by Camila Canales, Leyla Gidi, Roxana Arce, Francisco Armijo, María J. Aguirre and Galo Ramírez

Catalysts 2018, 8(12), 629; https://doi.org/10.3390/catal8120629 - 06 Dec 2018

Cited by 2 | Viewed by 3139

Abstract

The oxygen reduction reaction (ORR) is the most important reaction in life processes and in energy transformation. The following work presents the design of a new electrode which is composed by deposited cobalt octaethylporphyrin onto glassy carbon and graphene, where both carbonaceous materials [...] Read more.

The oxygen reduction reaction (ORR) is the most important reaction in life processes and in energy transformation. The following work presents the design of a new electrode which is composed by deposited cobalt octaethylporphyrin onto glassy carbon and graphene, where both carbonaceous materials have been electrochemically oxidized prior to the porphyrin deposition. The novel generated system is stable and has an electrocatalytic effect towards the oxygen reduction reaction, as a result of the significant overpotential shift in comparison to the unmodified electrode and to the electrodes used as target. Kinetic studies corroborate that the system is capable of reducing molecular oxygen via four electrons, with a Tafel slope value of 60 mV per decade. The systems were morphologically characterized by scanning electron microscopy (SEM) and atomic force microscopy (AFM) Electrochemical impedance spectroscopy studies showed that the electrode previously oxidized and modified with cobalt porphyrin is the system that possesses lower resistance to charge transfer and higher capacitance. Full article

(This article belongs to the Special Issue Immobilized Non-Precious Electrocatalysts for Advanced Energy Devices)

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9 pages, 4055 KiB

Open AccessArticle

Heteroatom (Nitrogen/Sulfur)-Doped Graphene as an Efficient Electrocatalyst for Oxygen Reduction and Evolution Reactions

by Jian Zhang, Jia Wang, Zexing Wu, Shuai Wang, Yumin Wu and Xien Liu

Catalysts 2018, 8(10), 475; https://doi.org/10.3390/catal8100475 - 19 Oct 2018

Cited by 17 | Viewed by 3684

Abstract

Carbon nanomaterials are potential materials with their intrinsic structure and property in energy conversion and storage. As the electrocatalysts, graphene is more remarkable in electrochemical reactions. Additionally, heteroatoms doping with metal-free materials can obtain unique structure and demonstrate excellent electrocatalytic performance. In this [...] Read more.

Carbon nanomaterials are potential materials with their intrinsic structure and property in energy conversion and storage. As the electrocatalysts, graphene is more remarkable in electrochemical reactions. Additionally, heteroatoms doping with metal-free materials can obtain unique structure and demonstrate excellent electrocatalytic performance. In this work, we proposed a facile method to prepare bifunctional electrocatalyst which was constructed by nitrogen, sulfur doped graphene (NSG), which demonstrate superior properties with high activity and excellent durability compared with Pt/C and IrO₂ for oxygen reduction (OR) and oxygen evolution (OE) reactions. Accordingly, these phenomena are closely related to the synergistic effect of doping with nitrogen and sulfur by rationally regulating the polarity of carbon in graphene. The current work expands the method towards carbon materials with heteroatom dopants for commercialization in energy-related reactions. Full article

(This article belongs to the Special Issue Immobilized Non-Precious Electrocatalysts for Advanced Energy Devices)

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Review

Jump to: Editorial, Research

16 pages, 1895 KiB

Open AccessReview

Review of Anodic Catalysts for SO₂ Depolarized Electrolysis for “Green Hydrogen” Production

by Sergio Díaz-Abad, María Millán, Manuel A. Rodrigo and Justo Lobato

Catalysts 2019, 9(1), 63; https://doi.org/10.3390/catal9010063 - 09 Jan 2019

Cited by 47 | Viewed by 5694

Abstract

In the near future, primary energy from fossil fuels should be gradually replaced with renewable and clean energy sources. To succeed in this goal, hydrogen has proven to be a very suitable energy carrier, because it can be easily produced by water electrolysis [...] Read more.

In the near future, primary energy from fossil fuels should be gradually replaced with renewable and clean energy sources. To succeed in this goal, hydrogen has proven to be a very suitable energy carrier, because it can be easily produced by water electrolysis using renewable energy sources. After storage, it can be fed to a fuel cell, again producing electricity. There are many ways to improve the efficiency of this process, some of them based on the combination of the electrolytic process with other non-electrochemical processes. One of the most promising is the thermochemical hybrid sulphur cycle (also known as Westinghouse cycle). This cycle combines a thermochemical step (H₂SO₄ decomposition) with an electrochemical one, where the hydrogen is produced from the oxidation of SO₂ and H₂O (SO₂ depolarization electrolysis, carried out at a considerably lower cell voltage compared to conventional electrolysis). This review summarizes the different catalysts that have been tested for the oxidation of SO₂ in the anode of the electrolysis cell. Their advantages and disadvantages, the effect of platinum (Pt) loading, and new tendencies in their use are presented. This is expected to shed light on future development of new catalysts for this interesting process. Full article

(This article belongs to the Special Issue Immobilized Non-Precious Electrocatalysts for Advanced Energy Devices)

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