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14 pages, 5122 KiB

Open AccessArticle

Enhanced Platinum-Based Thin-Film Catalysts for Electro-Oxidation of Methanol

by Dušan V. Tripković, Dragana L. Milošević, Sanja I. Stevanović, Ksenija Dj. Popović and Vladislava M. Jovanović

Materials 2024, 17(22), 5575; https://doi.org/10.3390/ma17225575 - 15 Nov 2024

Viewed by 406

Abstract

Surface morphology is one of the critical factors affecting the performance of electrocatalysts. Thus, with careful manipulation of the surface structures at the atomic level, the effectiveness of the catalyst can be significantly improved. Heat treatment is an effective method for inducing surface [...] Read more.

Surface morphology is one of the critical factors affecting the performance of electrocatalysts. Thus, with careful manipulation of the surface structures at the atomic level, the effectiveness of the catalyst can be significantly improved. Heat treatment is an effective method for inducing surface atom rearrangement, hence modifying the catalyst’s characteristics. This study investigated the substrate’s influence and the effect of thermal annealing on the morphology and surface reconstruction of platinum (Pt) thin-film catalysts. Our findings indicate that heat treatment in a reductive atmosphere (95% Ar + 5% H₂) at 300 °C can significantly impact the degree of rearrangement of surface atoms. This process induces long-range ordering, resulting in domains with a high proportion of (111) and (100) sites without an epitaxial template. Considering that the reactivity of low-index platinum single crystals for the methanol oxidation reaction follows the following sequence Pt(111) < Pt(110) < Pt(100), increasing the proportion of (100) planes leads to a notable enhancement (up to three times) in performance, compared to untreated catalysts. Furthermore, considering the amount of precious metal consumed, a mass-specific current density obtained on annealed Pt@Ni is larger by one order of magnitude and ~2 times that obtained on Pt@Cr and Pt@GC_ox catalysts, respectively. Our results demonstrate that an easy-to-implement way of controlling atomic orientations improves catalyst performance. With this contribution, we propose a method for designing improved electrocatalysts, as catalytic reactions occur only at the surface. Full article

(This article belongs to the Special Issue Advanced Electrocatalytic Materials for Energy and Environmental Applications)

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18 pages, 5803 KiB

Open AccessArticle

Shape–Preserved CoFeNi–MOF/NF Exhibiting Superior Performance for Overall Water Splitting across Alkaline and Neutral Conditions

by Yu Liu, Panpan Li, Zegao Wang and Liangjuan Gao

Materials 2024, 17(10), 2195; https://doi.org/10.3390/ma17102195 - 7 May 2024

Cited by 1 | Viewed by 1239

Abstract

This study reported a multi–functional Co_0.45Fe_0.45Ni_0.9–MOF/NF catalyst for oxygen evolution reaction (OER), hydrogen evolution reaction (HER), and overall water splitting, which was synthesized via a novel shape–preserving two–step hydrothermal method. The resulting bowknot flake structure on NF [...] Read more.

This study reported a multi–functional Co_0.45Fe_0.45Ni_0.9–MOF/NF catalyst for oxygen evolution reaction (OER), hydrogen evolution reaction (HER), and overall water splitting, which was synthesized via a novel shape–preserving two–step hydrothermal method. The resulting bowknot flake structure on NF enhanced the exposure of active sites, fostering a superior electrocatalytic surface, and the synergistic effect between Co, Fe, and Ni enhanced the catalytic activity of the active site. In an alkaline environment, the catalyst exhibited impressive overpotentials of 244 mV and 287 mV at current densities of 50 mA cm⁻² and 100 mA cm⁻², respectively. Transitioning to a neutral environment, an overpotential of 505 mV at a current density of 10 mA cm⁻² was achieved with the same catalyst, showing a superior property compared to similar catalysts. Furthermore, it was demonstrated that Co_0.45Fe_0.45Ni_0.9–MOF/NF shows versatility as a bifunctional catalyst, excelling in both OER and HER, as well as overall water splitting. The innovative shape–preserving synthesis method presented in this study offers a facile method to develop an efficient electrocatalyst for OER under both alkaline and neutral conditions, which makes it a promising catalyst for hydrogen production by water splitting. Full article

(This article belongs to the Special Issue Advanced Electrocatalytic Materials for Energy and Environmental Applications)

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13 pages, 2290 KiB

Open AccessArticle

Study of the Durability of Membrane Electrode Assemblies in Various Accelerated Stress Tests for Proton-Exchange Membrane Water Electrolysis

by Zhengquan Su, Jun Liu, Pengfei Li and Changhao Liang

Materials 2024, 17(6), 1331; https://doi.org/10.3390/ma17061331 - 14 Mar 2024

Cited by 1 | Viewed by 1879

Abstract

In this work, we focus on the degradation of membrane electrode assemblies (MEAs) in proton-exchange membrane water electrolysis (PEMWE) induced by different accelerated stress tests (ASTs), including constant-current mode, square-wave mode, and solar photovoltaic mode. In constant-current mode, at continuous testing for 600 [...] Read more.

In this work, we focus on the degradation of membrane electrode assemblies (MEAs) in proton-exchange membrane water electrolysis (PEMWE) induced by different accelerated stress tests (ASTs), including constant-current mode, square-wave mode, and solar photovoltaic mode. In constant-current mode, at continuous testing for 600 h at 80 °C, a degradation of operating voltage increased by the enhanced current density from 22 µV/h (1 A/cm²) to 50 µV/h (3 A/cm²). In square-wave mode, we found that in the narrow fluctuation range (1–2 A/cm²), the shorter step time (2 s) generates a higher degradation rate of operating voltage, but in the wide fluctuation range (1–3 A/cm²), the longer step time (22 s) induces a faster operating voltage rise. In the solar photovoltaic mode, we used a simulation of 11 h sunshine duration containing multiple constant-current and square-wave modes, which is closest to the actual application environment. Over 1400 h ASTs, the solar photovoltaic mode lead to the most serious voltage rise of 87.7 µV/h. These results are beneficial to understanding the durability of the PEM electrolyzer and optimizing the components of MEAs, such as catalysts, membranes, and gas diffusion layers. Full article

(This article belongs to the Special Issue Advanced Electrocatalytic Materials for Energy and Environmental Applications)

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15 pages, 6417 KiB

Open AccessArticle

Iodine-Doped Hollow Carbon Nanocages without Templates Strategy for Boosting Zinc-Ion Storage by Nucleophilicity

by Ruiting Niu, Huailin Fan, Qingfu Ban, Dezhi Zhou, Lekang Zhao, Jiayuan Yu, Qifeng Chen and Xun Hu

Materials 2024, 17(4), 838; https://doi.org/10.3390/ma17040838 - 9 Feb 2024

Viewed by 1009

Abstract

Zn-ion hybrid supercapacitors (ZHCs) combining merits of battery-type and capacitive electrodes are considered to be a prospective candidate in energy storage systems. Tailor-made carbon cathodes with high zincophilicity and abundant physi/chemisorption sites are critical but it remains a great challenge to achieve both [...] Read more.

Zn-ion hybrid supercapacitors (ZHCs) combining merits of battery-type and capacitive electrodes are considered to be a prospective candidate in energy storage systems. Tailor-made carbon cathodes with high zincophilicity and abundant physi/chemisorption sites are critical but it remains a great challenge to achieve both features by a sustainable means. Herein, a hydrogen-bonding interaction-guided self-assembly strategy is presented to prepare iodine-doped carbon nanocages without templates for boosting zinc-ion storage by nucleophilicity. The biomass ellagic acid contains extensional hydroxy and acyloxy groups with electron-donating ability, which interact with melamine and ammonium iodide to form organic supermolecules. The organic supermolecules further self-assemble into a nanocage-like structure with cavities under hydrothermal processes via hydrogen-bonding and π-π stacking. The carbon nanocages as ZHCs cathodes enable the high approachability of zincophilic sites and low ion migration resistance resulting from the interconnected conductive network and nanoscale architecture. The experimental analyses and theoretical simulations reveal the pivotal role of iodine dopants. The I₅⁻/I₃⁻ doping anions in carbon cathodes have a nucleophilicity to preferentially adsorb the Zn²⁺ cation by the formation of C⁺-I₅⁻-Zn²⁺ and C⁺-I₃⁻-Zn²⁺. Of these, the C⁺-I₃⁻ shows stronger bonding with Zn²⁺ than C⁺-I₅⁻. As a result, the iodine-doped carbon nanocages produced via this template-free strategy deliver a high capacity of 134.2 mAh/g at 1 A/g and a maximum energy and power density of 114.1 Wh/kg and 42.5 kW/kg. Full article

(This article belongs to the Special Issue Advanced Electrocatalytic Materials for Energy and Environmental Applications)

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12 pages, 3697 KiB

Open AccessArticle

Sustainable Utilization of Fe(Ⅲ) Isolated from Laterite Hydrochloric Acid Lixivium via Ultrasonic-Assisted Precipitation to Synthesize LiFePO₄/C for Batteries

by Ziyang Xu, Boren Tan, Boyuan Zhu, Guangye Wei, Zhihui Yu and Jingkui Qu

Materials 2024, 17(2), 342; https://doi.org/10.3390/ma17020342 - 10 Jan 2024

Cited by 2 | Viewed by 1096

Abstract

Ultrasonic-assisted precipitation was employed to sustainably isolate Fe in the hydrochloric acid lixivium of low-grade laterite for the synthesis of battery-grade iron phosphate. The recovery efficiency of Ni and Co exceeded 99%, while the removal efficiency of the Fe impurity reached a maximum [...] Read more.

Ultrasonic-assisted precipitation was employed to sustainably isolate Fe in the hydrochloric acid lixivium of low-grade laterite for the synthesis of battery-grade iron phosphate. The recovery efficiency of Ni and Co exceeded 99%, while the removal efficiency of the Fe impurity reached a maximum of 95%. Precipitation parameters for the selective isolation of Fe (MgO precipitant, pH 1, 70–80 °C) were optimized and used in ultrasonic precipitation experiments. The use of ultrasonic waves in the precipitation process enhanced micromixing by reducing the size of primary grains and mitigating particle agglomeration, thereby significantly improving the purity of the isolated compound and providing high-quality iron phosphate (FePO₄·2H₂O). The LiFePO₄/C composite prepared from as-precipitated FePO₄ exhibited excellent electrochemical performance, with a discharge capacity of 149.7 mAh/g at 0.1 C and 136.3 mAh/g at 0.5 C after 100 cycles, retaining almost 100% cycling efficiency. This novel and facile method for iron removal from laterite acid lixivium not only efficiently removes excess iron impurities leached due to the poor selectivity of hydrochloric acid, but also enables the high-value utilization of these iron impurities. It enhances economic benefits while simultaneously alleviating environmental pressure. Full article

(This article belongs to the Special Issue Advanced Electrocatalytic Materials for Energy and Environmental Applications)

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11 pages, 2184 KiB

Open AccessArticle

Reasonable Design of MXene-Supported Dual-Atom Catalysts with High Catalytic Activity for Hydrogen Evolution and Oxygen Evolution Reaction: A First-Principles Investigation

by Erpeng Wang, Miaoqi Guo, Jian Zhou and Zhimei Sun

Materials 2023, 16(4), 1457; https://doi.org/10.3390/ma16041457 - 9 Feb 2023

Cited by 15 | Viewed by 2986

Abstract

MXene-supported single-atom catalysts (SACs) for water splitting has attracted extensive attention. However, the easy aggregation of individual metal atoms used as catalytic active centers usually leads to the relatively low loading of synthetic SACs, which limits the development and application of SACs. Herein, [...] Read more.

MXene-supported single-atom catalysts (SACs) for water splitting has attracted extensive attention. However, the easy aggregation of individual metal atoms used as catalytic active centers usually leads to the relatively low loading of synthetic SACs, which limits the development and application of SACs. Herein, by performing first-principles calculations for Pt and 3d transition metal single atoms immobilized on a two-dimensional (2D) Mo₂TiC₂O₂ MXene surface, we systematically studied the performance of heterogeneous dual-atom catalysts (h-DACs) in hydrogen evolution reaction (HER) and oxygen evolution reaction (OER). Significantly, h-DACs exhibit higher metal atom loading and more flexible active sites compared to SACs. Benefiting from these features, we found that Pt/Cu@Mo₂TiC₂O₂ heterogeneous DACs exhibits excellent HER activity with ultra-low overpotential |ΔG_H^∗| (0.04 eV), lower than the corresponding Pt@Mo₂TiC₂O₂ (0.14 eV) and Cu@Mo₂TiC₂O₂ (0.33 eV) SACs, and even lower than that of Pt (0.09 eV). Meanwhile, Pt/Ni@Mo₂TiC₂O₂ exhibits superior OER activity with ultra-low overpotential η^OER (0.38 V), lower than that of Pt@Mo₂TiC₂O₂ (1.11 V) and Ni@Mo₂TiC₂O₂ (0.57 V) SACs, and even lower than that of RuO₂ (0.42 V) and IrO₂ (0.56 V). Our finding paves the way for the rational design of h-DACs for HER and OER with excellent activity, which provides guidance for other catalytic reactions. Full article

(This article belongs to the Special Issue Advanced Electrocatalytic Materials for Energy and Environmental Applications)

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16 pages, 5090 KiB

Open AccessReview

Design Strategy of Corrosion-Resistant Electrodes for Seawater Electrolysis

by Li Zhao, Xiao Li, Jiayuan Yu and Weijia Zhou

Materials 2023, 16(7), 2709; https://doi.org/10.3390/ma16072709 - 28 Mar 2023

Cited by 9 | Viewed by 4481

Abstract

Electrocatalytic water splitting for hydrogen (H₂) production has attracted more and more attention in the context of energy shortages. The use of scarce pure water resources, such as electrolyte, not only increases the cost but also makes application difficult on a [...] Read more.

Electrocatalytic water splitting for hydrogen (H₂) production has attracted more and more attention in the context of energy shortages. The use of scarce pure water resources, such as electrolyte, not only increases the cost but also makes application difficult on a large scale. Compared to pure water electrolysis, seawater electrolysis is more competitive in terms of both resource acquisition and economic benefits; however, the complex ionic environment in seawater also brings great challenges to seawater electrolysis technology. Specifically, chloride oxidation-related corrosion and the deposition of insoluble solids on the surface of electrodes during seawater electrolysis make a significant difference to electrocatalytic performance. In response to this issue, design strategies have been proposed to improve the stability of electrodes. Herein, basic principles of seawater electrolysis are first discussed. Then, the design strategy for corrosion-resistant electrodes for seawater electrolysis is recommended. Finally, a development direction for seawater electrolysis in the industrialization process is proposed. Full article

(This article belongs to the Special Issue Advanced Electrocatalytic Materials for Energy and Environmental Applications)

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25 pages, 4830 KiB

Open AccessReview

Killing Two Birds with One Stone: Upgrading Organic Compounds via Electrooxidation in Electricity-Input Mode and Electricity-Output Mode

by Jiamin Ma, Keyu Chen, Jigang Wang, Lin Huang, Chenyang Dang, Li Gu and Xuebo Cao

Materials 2023, 16(6), 2500; https://doi.org/10.3390/ma16062500 - 21 Mar 2023

Viewed by 2620

Abstract

The electrochemically oxidative upgrading reaction (OUR) of organic compounds has gained enormous interest over the past few years, owing to the advantages of fast reaction kinetics, high conversion efficiency and selectivity, etc., and it exhibits great potential in becoming a key element in [...] Read more.

The electrochemically oxidative upgrading reaction (OUR) of organic compounds has gained enormous interest over the past few years, owing to the advantages of fast reaction kinetics, high conversion efficiency and selectivity, etc., and it exhibits great potential in becoming a key element in coupling with electricity, synthesis, energy storage and transformation. On the one hand, the kinetically more favored OUR for value-added chemical generation can potentially substitute an oxygen evolution reaction (OER) and integrate with an efficient hydrogen evolution reaction (HER) or CO₂ electroreduction reaction (CO₂RR) in an electricity-input mode. On the other hand, an OUR-based cell or battery (e.g., fuel cell or Zinc–air battery) enables the cogeneration of value-added chemicals and electricity in the electricity-output mode. For both situations, multiple benefits are to be obtained. Although the OUR of organic compounds is an old and rich discipline currently enjoying a revival, unfortunately, this fascinating strategy and its integration with the HER or CO₂RR, and/or with electricity generation, are still in the laboratory stage. In this minireview, we summarize and highlight the latest progress and milestones of the OUR for the high-value-added chemical production and cogeneration of hydrogen, CO₂ conversion in an electrolyzer and/or electricity in a primary cell. We also emphasize catalyst design, mechanism identification and system configuration. Moreover, perspectives on OUR coupling with the HER or CO₂RR in an electrolyzer in the electricity-input mode, and/or the cogeneration of electricity in a primary cell in the electricity-output mode, are offered for the future development of this fascinating technology. Full article

(This article belongs to the Special Issue Advanced Electrocatalytic Materials for Energy and Environmental Applications)

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