Engineered 2D materials for oxygen evolution reaction (OER)

The development of renewable energy conversion and storage has triggered the development of electrode materials for oxygen evolution reaction (OER) and supercapacitors. Here we report a highly active Cu doped NiFe nanosheets hydroxide electrode with rich oxygen vacancies (OVs) (denoted as H-NiFeCuO/NF) prepared by in situ anodic electrodeposition on the three-dimensional macroporous nickel foam (NF) substrate followed by heat treatment with H2. The as-prepared H-NiFeCuO/NF electrode showed the initial potential of 1.44 V (versus RHE) for OER and 980 F g−1 specific capacity as supercapacitor in 1 M KOH. Further investigation suggested that the tuning of composition and structure by doping copper ions and creating OVs helped accelerate the electrochemical reactions. This practice provides an efficient approach for the fabrication of heteromultimetallic hydroxide monolithic electrode with high performance in OER or supercapacitor application.

Open AccessRenewablesREVIEWS24 Jan 2023Two-dimensional materials for high-performance oxygen evolution reaction: fundamentals, recent progresses and improving strategies Xiong Yin, Yani Hua and Zhan Gao Xiong Yin Google Scholar More articles by this author , Yani Hua Google Scholar More articles by this author and Zhan Gao Google Scholar More articles by this author https://doi.org/10.31635/renewables.023.202200003 SectionsAboutPDF ToolsAdd to favoritesDownload CitationsTrack Citations ShareFacebookTwitterLinked InEmail Oxygen evolution reaction (OER) has an essential role in many energy storage and conversion technologies, but its high overpotential and sluggish kinetics seriously astrict the energy efficiency. The development of efficient and inexpensive OER electrocatalysts is still a grand challenge. Two-dimensional (2D) materials with unique structure and electronic properties have wide application prospects toward OER. In this review, firstly introducing OER electrocatalytic mechanisms and some crucial parameters for evaluating OER electrocatalysts, the latest progresses in the design and construction of 2D materials for OER is systematically reviewed, including layered double hydroxides, 2D carbon materials, transition metal dichalcogenides, metal oxide and phosphide nanosheets, metal-organic frameworks, covalent-organic frameworks and MXenes. Emphatically, some effective design and optimization strategies to improve electrocatalytic activity and durability of 2D materials as OER electrocatalysts are comprehensively generalized. The advantages and shortcomings of these 2D materials are analyzed in detail and their practical applications are deeply understood, which is crucial for the rational design of high-performance OER electrocatalysts. Finally, the challenges and future development opportunities of 2D materials for enhanced OER are discussed. Our review is expected to provide certain guidance for the development of new low-cost 2D materials as advanced OER electrocatalysts. Download figure Download PowerPoint Previous articleNext article FiguresReferencesRelatedDetails Issue AssignmentNot Yet Assigned Copyright & Permissions© 2023 Chinese Chemical Society Downloaded 0 times PDF downloadLoading ...

Efficient nonprecious‐metal oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) electrocatalysts are key for the commercial viability of fuel cells, metal–air batteries, and water‐splitting systems. Thus, high‐performance ORR and OER electrocatalysts in acidic electrolytes are needed to support high‐efficiency proton exchange membrane (PEM)‐based systems. Herein, we report a new approach to design and prepare an ultrathin N‐doped holey carbon layer (HCL) on a graphene sheet that exhibits outstanding bifunctional ORR/OER activities in both alkaline and acidic media. The edge sites of HCL are utilized to achieve selective doping of highly active pyridinic‐N. The sandwiched graphene sheet provides mechanical support, stabilizes HCL structure and promotes charge transfer. The synergetic effect of the catalyst structure overcomes the drawbacks of holey graphene approaches. The resulting ORR and OER performances are equal to or better than the top‐ranked electrocatalysts.

The facile exfoliation of a two-dimensional metal-organic nanosheet of {[Co(HL)(H2O)(Py)3/4]·1/2H2O·DMF}n [1-Py; H3L = 5-(1H-pyrazol-4-yl)isophthalic acid and Py = pyridine] was achieved, via a molecular scalpel strategy, by weakening intermolecular forces between adjacent layers. The resulting 1-Py/KB40 (KB = Ketjen black) shows an increased oxygen evolution reaction (OER) performance with an overpotential of 370 mV at a current density of 10 mA cm-2 and a Tafel slope of 58 mV dec-1. This work sheds light on the structure-morphology-reactivity relationship of such materials in OER.

One-step construction of FeNi LDH/FeNi2S4 heterojunctions for boosting electrocatalytic oxygen evolution reaction and hybrid capacitive storage

Multiple important electrochemical processes including hydrogen generation from water reply on acid-stable electrocatalysts for oxygen evolution reaction (OER). The material choice of OER electrocatalysts in acid is often limited to only two major types of oxides (e.g., RuO2 and IrO2). Recently, ternary compounds have been reported to have excellent OER performance. Among them, our group developed pyrochlore-type electrocatalysts of various compositions. Yttrium ruthenate (Y2Ru2O7-δ) was shown to have significantly enhanced performance towards OER in acid media over both RuO2 and IrO2 catalysts at current density about 1 mA/cm2 [1]. It has an onset overpotential of 190 mV in 0.1-M perchloric acid solution. Tafel plots show the Y2Ru2O7-δ catalyst had enhanced activity from 55 mV/dec for the first cycle to 46 mV/dec for the 10,000th cycle. In comparison, the OER performance for RuO2 catalyst degraded from 61 mV/dec for the first cycle to 72 mV/dec for the 10,000th cycle under the same testing conditions. A range of techniques including X-ray absorption spectroscopy (XAS) and computational tools such as density functional theory (DFT) calculation have been used to understand the structural origins of enhanced performance. Our preliminary data suggest a low valence state in yttrium ruthenate (Y2Ru2O7-δ) favors the high OER activity, while lowered band center energy for the overlap between Ru 4d and O 2p orbitals contributes to the stability. A systematic study on the structural origin for high OER performance has further been carried out using a series of A2Ru2O7-δ pyrochlore-type electrocatalysts and will be presented in this talk. Strategies for improving the overall performance of these OER catalysts will also be discussed [2,3].

Highly active, stable, and cut-price (photo-)electrocatalysts are desired to overwhelm high energy barriers for anodic oxygen evolution reaction processes. Herein, a heterostructure of cobalt-iron oxide/black phosphorus nanosheets is in-situ synthesized via a facile and novel three-electrode electrolysis method. Bulky black phosphorus is exfoliated into its nanosheets at the cathode while the CoFe oxide is derived directly from the metal wire anode during the electrolysis process. This heterostructure exhibits excellent electrocatalytic oxygen evolution reaction (OER) performance, and the overpotential at 10 mA·cm−2 is 51 mV lower than that of the commercial RuO2 catalyst. Its superior OER performance stems from the favorable adsorption behavior and an enlarged electrochemical active surface area of the catalyst. To reveal the origin of excellent OER performance from the point of adsorption strength of OH*, methanol oxidation reaction (MOR) test is applied under the identified OER operating conditions. Further introduction of light illumination enhances the OER activity of this heterostructure. The overpotential drops down to 280 mV, benefiting from pronounced photochemical response of black phosphorus nanosheets and iron oxide inside the heterostructure. This work develops a new electrochemical method to construct high performance and light-sensitive heterostructures from black phosphorus nanosheets for the OER.

The active phase and catalytic mechanisms of Ni-based layered double hydroxide (LDH) materials for oxygen evolution reaction (OER) have no common consensus and remain controversial. Moreover, engineering the site activity and the number of active sites of LDHs is an efficient approach to advance the OER activity, as the thickness and stacking structure of the LDHs layer limit the catalytic activity. This work presents an interesting in situ approach of tuning the site activity and number of active sites of NiMn-LDHs, which exhibit the superior OER performance (onset overpotential of 0.17 V and overpotential of 0.24 V at 10 mA cm-2). The fundamental mechanistic insights and active phases during the OER process are characterized by in operando techniques along with the computational density functional theory calculations, revealing that the Ni site constitutes the OER activity and the dynamically generated NiOOH moiety is the active phase. We also prove that Ni sites undergo a reversible oxidation state under the working conditions to create active NiOOH species which catalyze the water to generate oxygen. These findings suggest that the Ni(III) phase in NiMn-LDHs is the OER active site and Mn promotes the electronic properties of Ni sites. Utilizing in situ/in operando techniques and theoretical calculation, we find that the in situ intercalation of guest anions allows the expansion of the LDH layers and keeps the active NiOOH species under the oxidation state of +3 via electron coupling, which ultimately tunes the site populations and site activity toward the superior OER activity, respectively. This work thus targets to provide insight into strategies to design the next generation of highly active catalysts for water electrolysis and fuel cell technologies.

Cobalt oxides find widespread application in energy materials as oxygen evolution catalysts (OECs) in the oxygen evolution reaction (OER) and photocatalytic overall water splitting (OWS) reaction. However, the nature of the active cobalt species, their role in these reactions, and possible commonalities remain poorly understand. Here, the impact of (redox-inert) germanium dopants on the physicochemical properties of Co3O4 nanoparticles was investigated in electrochemical oxygen evolution and photocatalytic OWS reactions. A significant enhancement in OER performance on doping is attributed to the restructuring of spinel Co3O4 to serpentine Co3Ge2(OH)5, with the latter transforming to an oxyhydroxide active phase during OER. Combination of the p-type Co3Ge2(OH)5 semiconductor as an OEC with an n-type Bi0.5Y0.5VO4 semiconductor doubles the photocatalytic OWS activity of the latter, resulting in H2 and O2 productivities of ∼175.7 and ∼90.1 μmol/h, respectively. Formation of the composite semiconductor induces an intense internal electric field across the p–n junction, facilitating separation of photogenerated carriers and increased OWS activity, which is also validated in alternative photocatalyst, Al-doped SrTiO3. A similar transformation of serpentine Co3Ge2(OH)5 to an oxyhydroxide was not observed during OWS, indicating that Ge doping confers distinct advantages for electrochemical OER vs photocatalytic OWS.

To meet the energy crisis of our modern society in context to the depletion of fossil fuels, oxygen evolution reaction become a potential and most investigated candidate for future energy storage and conversion technologies. Along the way, numerous highly efficient electrocatalysts have been developed to enhance the yield of oxygen production which has also triggered the investigation of novel, cost-effective material to overcome the slow kinetics and large overpotential of this process. Recently, a new class of two-dimensional carbides, nitrides, or carbonitrides, known as MXene, has attracted a significant attention as electrocatalyst due to their outstanding characteristics including high electrical conductivity, impressive stability, hydrophilicity, large surface area, and tuneable morphology. This chapter is intended for systematic summary on MXene preparation techniques, theoretical establishment, surface functionalization, morphology, structural, electrical, and electronic properties, and the application of MXene and its composites for oxygen evolution reaction. Moreover, it is concluded with captivating prospective and interpretation as well as significant limitations on MXene-based materials for oxygen evolution reaction.

Exploring the electrocatalytic performance of silicene and single atom doped silicene for HER, OER and ORR activity using density functional theory

The material design of highly active catalysts for energy storage applications (e.g., metal-air batteries and fuel cells) is crucial for solving global energy problems. The oxygen evolution reaction (OER) and the oxygen reduction reaction (ORR) is used for charging and discharging rechargeable metal-air batteries, respectively. Although precious metal-based catalysts facilitate these reactions, the kinetics of the OER and ORR are rather sluggish due to their multistep electron transfer. It is therefore important to explore the mechanism of the OER and ORR to discover the key factors for highly active catalysts. As demonstrated by Suntivich et al. (2011)[1],[2], when the number of electrons in the eg orbital is close to unity for transition metals, perovskite oxides exhibit maximum OER and ORR activities. In other words, Mn3+ (t2g 3 eg 1 for both surface and bulk), Co3+ (t2g 5 eg 1 for surface), and Ni3+ (t2g 6 eg 1 for both surface and bulk) become OER and ORR active sites for Mn3+, Co3+ and Ni3+ based compounds . However, LaMnO3 exhibits a significantly lower specific OER activity[3] compared with LaCoO3 and LaNiO3 (~6% of LaNiO3 at 1.8 V vs. RHE). Also, Mn3O4 exhibits a low specific OER activity[4] (40% of Mn2O3 at 1.8 V vs. RHE) similar to LaMnO3. It is therefore important to explore what causes degradation of the OER activity of Mn3+-based (t2g 3 eg 1) compounds to improve their catalytic activity. We attempt to improve the performance of Mn3+-based oxides by controlling the degradation factors of their OER activities. To directly compare the OER activities of Mn3+-based oxides containing more than two cation sites, Mn3+ concentrations at the octahedral site and their initial crystal structures were maintained. Mn3-x Co x O4 (0 ≤ x < 1), a series of tetragonally distorted spinel compounds, satisfies this condition, as their octahedral sites remain occupied by only Mn3+ ions . For Mn3+-based oxides with a single cation site, Mn3+ was directly substituted by Co3+.We systematically studied the OER and ORR performances of Mn3+-based oxides by Co3+-substitution. Nanoparticles were prepared for the evaluation of catalytic activity to minimize the influence of geometric factors. Electrochemical measurements were conducted using a rotating ring disk electrode rotator (RRDE-3A, BAS Inc., Japan) at 1600 rpm, in combination with a bipotentiostat (ALS Co., Ltd, Japan). In addition, a Pt wire counter electrode, and an Hg/HgO reference electrode (International Chemistry Co., Ltd., Japan) filled with 0.10 M KOH (Nacalai Tesque, Inc., Japan) were used. Electrochemical measurements were conducted with O2 saturation (30 min bubbling O2 gas through the solution) at ~25 °C, where the equilibrium potential of the O2/H2O redox couple was fixed at 0.304 V vs. Hg/HgO (or 1.23 V vs. RHE). During OER current density measurements for each sample, the potential of the sample-modified GC was controlled from 0.3-0.9 V vs. Hg/HgO (1.226-1.826 V vs. RHE) at 10 mV/s. For all measurements, the OER current density was iR-corrected (R = ~43 Ω) using the measured solution resistance, and capacitance-corrected by averaging the anodic and cathodic scans to remove the influence of the current related to the formation of an electrical double layer. With an increase in Co content, signicant improvements in the OER and ORR activities were observed for Mn3+-based oxides. For example, Mn2.1Co0.9O4 exhibited a high specific OER activity (1700 % of Mn3O4 at 1.76 V vs. RHE) and a long-term stability over 100 cycles [5]. The OER activities of Mn3+-based oxides increased linearly with the suppression of the Jahn–Teller distortion. We examined whether the electronic state of Mn3+ changes in favor of enhancing the OER and ORR activities. When the Jahn-Teller distortion of Mn3+O6 octahedra is suppressed due to the increase in Co content, the splitting of the Mn3+ eg orbitals becomes smaller and the electron occupying the Mn3+ eg orbital shifts to a higher energy level. Thus, the overlap of the antibonding Mn3+ eg orbitals with the O 2p orbitals of the oxygen adsorbate becomes stronger. The OER and ORR activities of Mn3+-based oxides should therefore be enhanced due to the stronger binding of OER intermediates to the catalytic surface. We therefore conclude that the suppression of Jahn–Teller distortion enhances the OER and ORR activities of Mn3+-based oxides. Our result suggests a future application of Mn3+-based oxides as bifunctional catalysts for metal-air batteries. [1] J. Suntivich et al., Science, 2011, 334, 1383. [2] J. Suntivich et al., Nature Chemistry, 2011, 3, 546. [3] B. Han et al., Phys. Chem. Chem. Phys., 2015, 17, 22576. [4] A. Ramirez et al., J. Phys. Chem. C, 2014, 118, 14073. [5] S. Hirai et al., RSC Adv., 2016, 6, 2019.

Preparing high‐efficiency, durable and low overpotential electrocatalytic materials for oxygen evolution reaction (OER) plays a key role in water electrolysis. At present, electrochemical water separation technology has become the most promising sustainable hydrogen production process. The inherent hysteresis kinetics of oxygen evolution reaction (OER) is the key bottleneck of water electrolysis, which greatly restricts the energy conversion efficiency and practical large‐scale application. Herein, a facile method is developed to synthesize a series of trimetallic (Mo/Ni/Fe) metal‐organic frameworks (MOFs)‐derived carbon nanoparticles (CNPs) with various Fe content, and a Fe‐dependent volcano‐type plot can be drawn out for MoNiFex‐CNPs. The optimized MoNiFe0.4‐CNPs demonstrate superior electrocatalytic performance with a low overpotential of only 227 mV@10 mA cm−2 and excellent durability of 100 h. Its excellent OER performance is attributed to the synergistic effect of Fe/Ni bimetallic regulated by Mo. This work improved the catalytic performance of MOFs in the OER and proposed a new strategy for the structural design of MOFs.

Increasing electrocatalytic efficiency of CuO/CoMn2O4 nanocomposite for oxygen evolution reaction

In situ electrochemically generated composite-type CoOx/WOx in self-activated cobalt tungstate nanostructures: implication for highly enhanced electrocatalytic oxygen evolution