非贵金属电催化析氧催化剂的最新进展

氢气具有环境友好、含量丰富、高能量密度等特点,是一种可以替代化石能源的绿色环保可再生能源. 电解水是制备氢气最有效途径之一. 但在电解水过程中,动力学过程非常缓慢,过电位较大的阳极析氧半反应严重限制了阴极析氢反应效率. 因此,研究高效、稳定和低成本的催化剂来降低析氧反应的过电位,从而提高析氢反应效率受到了广泛关注. 基于非贵金属催化剂本身特性及其在高浓度OH-条件下具有较高OER催化活性等原因,本文首先简要介绍碱性条件下析氧反应机理及其性能的评价方法,然后重点讨论非贵金属电催化析氧催化剂的最新研究进展. 最后对如何深入研究催化机理、设计高效、双功能及新型非贵金属电催化析氧催化剂进行了展望.     

Modulating the Electronic Structure of Porous Nanocubes Derived from Trimetallic Metal–Organic Frameworks to Boost Oxygen Evolution Reaction Performance

The preparation of noble metal‐free catalysts for water splitting is the key to low‐cost, sustainable hydrogen generation. Herein, through a pyrolysis‐oxidation process, we prepared a series of Co‐Fe‐Ni trimetallic oxidized carbon nanocubes (Co_1‐XFe_XNi‐OCNC) with a continuously changeable Co/Fe ratio (X=0, 0.1, 0.2, 0.5, 0.8, 0.9, 1). The Co_1‐XFe_XNi‐OCNC shows a volcano‐type oxygen evolution reaction (OER) activity. The optimized Co_0.1Fe_0.9Ni‐OCNC achieves a low overpotential of 268 mV at 10 mA cm^?2 with a very low Tafel slope of 48 mV dec^?1 in 1 m KOH. At the same time, the stability of the Co_0.1Fe_0.9Ni‐OCNC is also outstanding; after 1000 CV cycles, the LSV plot is almost coincident. Moreover, the potential remains almost of the same value at 10 mA cm^?2 after 12 h in comparison to the initial value. The excellent electrocatalytic properties can be attributed to the synergistic cooperation between each component. Therefore, the Co_0.1Fe_0.9Ni‐OCNC is a promising candidate instead of precious metal‐based electrocatalysts for OER.     

Bifunctional Catalysts for Reversible Oxygen Evolution Reaction and Oxygen Reduction Reaction

Metal-air batteries (MABs) and reversible fuel cells (RFCs) rely on the bifunctional oxygen catalysts for oxygen evolution reaction (OER) and oxygen reduction reaction (ORR). Finding efficient bifunctional oxygen catalysts is the ultimate goal and it has attracted a great deal of attention. The dilemma is that a good ORR catalyst is not necessarily efficient for OER, and vice versa. Thus, the development of a new type of bifunctional oxygen catalysts should ensure that the catalysts exhibit high activity for both OER and ORR. Composites with multicomponents for active centers supported on highly conductive matrices could be able to meet the challenges and offering new opportunities. In this Review, the evolution of bifunctional catalysts is summarized and discussed aiming to deliver high-performance bifunctional catalysts with low overpotentials.     

Adjustable Ternary FeCoNi Nanohybrids for Enhanced Oxygen Evolution Reaction

Water splitting as a greatly desired technology to produce clean renewable energy, but is hampered by the sluggish oxygen evolution reaction. So, the development of highly active and durable water oxidation electrocatalysts is of primarily significance for energy conversion. Here, a facial strategy to synthesize FeCoNi nanohybrids with adjustable morphological structures by using fluorine is introduced. The morphology and electrocatalytic activity of the sample is determined by the innovative introduction of fluorine. Among them, the overpotential at 10 mA cm⁻² of the best sample is approximately 97 mV lower than the commercial RuO₂ toward the oxygen evolution reaction in 1 m KOH. Additionally, the catalysts also have low Tafel slopes and remarkable stability.     

用于电催化析氧反应电极的制备策略

随着能源枯竭和环境污染等问题的日益严重,开发清洁可再生能源及相关新型技术迫在眉睫。近年来,水分解、金属-空气电池等电化学能源储存和转换技术得到人们的广泛关注。电催化析氧反应(Oxygen evolution reaction,OER)是其中的一个关键反应,大量高性能的OER电催化剂不断见诸报道。除了材料本征催化活性的影响,不同的电极制备方式同样会对催化剂性能的发挥起到重要作用,越来越多的研究者致力于探索高效OER电极的设计与制备方法。本综述从方法论的角度,详细介绍了目前高效OER电极的制备策略,讨论了各类制备方式的优势和不足,总结了相关工作的最新研究进展,概述了新型电极的制备方法。最后,对电极制备策略的发展方向进行了总结与展望。     

NiSe2-CoSe2 with a Hybrid Nanorods and Nanoparticles Structure for Efficient Oxygen Evolution Reaction

Hetero-structure induced high performance catalyst for oxygen evolution reaction(OER)in the water splitting reaction has received increased attention.Herein,we demonstrated a novel catalyst system of NiSe₂-CoSe₂ consisting of nanorods and nanoparticles for the efficient OER in the alkaline electrolyte.This catalyst system can be easily fabricated via a low-temperature selenization of the solvothermal synthesized NiCo(OH)x precursor and the unique morphology of hybrid nanorods and nanoparticles was found by the electron microscopy analysis.The high valence state of the metal species was indicated by X-ray photoelectron spectroscopy study and a strong electronic effect was found in the NiSe₂-CoSe₂ catalyst system compared to their counterparts.As a result,NiSe₂-CoSe₂ exhibited high catalytic performance with a low overpotential of 250 mV to reach 10 mA·cm^-2 for OER in the alkaline solution.Furthermore,high catalytic stability and catalytic kinetics were also observed.The superior performance can be attributed to the high valence states of Ni and Co and their strong synergetic coupling effect between the nanorods and nanoparticles,which could accelerate the charge transfer and offer abundant electrocatalytic active sites.The current work offers an efficient hetero-structure catalyst system for OER,and the results are helpful for the catalysis understanding.     

Spontaneous Synthesis of Silver‐Nanoparticle‐Decorated Transition‐Metal Hydroxides for Enhanced Oxygen Evolution Reaction

The fabrication of metal‐supported hybrid structures with enhanced properties typically requires external energy input, such as pyrolysis, photolysis, and electrodeposition. In this study, silver‐nanoparticle‐decorated transition‐metal hydroxide (TMH) composites were synthesized by an approach based on a spontaneous redox reaction (SRR) at room temperature. The SRR between silver ions and TMH provides a simple and facile route to establish effective and stable heterostructures that can enhance the oxygen evolution reaction (OER) activity. Ag@Co(OH)_x grown on carbon cloth exhibits outstanding OER activity and durability, even superior to IrO₂ and many previously reported OER electrocatalysts. Experimental and theoretical analysis demonstrates that the strong electronic interaction between Ag and Co(OH)₂ activates the silver clusters as catalytically OER active sites, effectively optimizing the binding energies with reacted intermediates and facilitating the OER kinetics.     

Vertically Aligned Porous Nickel(II) Hydroxide Nanosheets Supported on Carbon Paper with Long‐Term Oxygen Evolution Performance

Vertically aligned Ni(OH)₂ nanosheets were grown on carbon paper (CP) current collectors through a simple and cost‐effective hydrothermal approach. The as‐grown nanosheets are porous and highly crystallized. If used as a monolithic electrode for electrochemical water oxidation in alkaline solution, the carbon paper supported Ni(OH)₂ nanosheets [CP@Ni(OH)₂] exhibit high electrocatalytic activity and excellent long‐term stability. The electrode can attain an anodic current density of 20 mA cm⁻² at a low overpotential of 338 mV, comparable to that of state‐of‐the‐art RuO₂ nanocatalysts supported on CP (CP/RuO₂) with the same catalyst loading. Significantly, CP@Ni(OH)₂ shows much better long‐term stability than CP/RuO₂ upon continuous galvanostatic electrolysis, particularly at a high industry‐relevant current density such as 100 mA cm⁻². CP@Ni(OH)₂ can sustain water oxidation at 100 mA cm⁻² for 50 h without any degradation, whereas the performance of CP/RuO₂ is much poorer and deteriorates gradually over time. CP@Ni(OH)₂ electrodes hold substantial promise for use as low‐costing water oxidation anodes in electrolyzers.     

镍铁水滑石电催化氧析出研究进展

氧析出反应(Oxygen evolution reaction, OER)是电解水制氢、二氧化碳还原、二次金属-空气电池等能源储存和转化技术中的关键半反应。镍铁水滑石类材料(NiFe layered double hydroxide, NiFe-LDH)具有独特的层状结构、优异的催化性能和成本低廉等优点,是一类极具潜力的OER催化材料。但电导率低、活性位点暴露不充分等缺点也限制了其催化性能的进一步提高。本文综述了包括引入缺陷、片层剥离、元素掺杂、表面修饰和原位生长等针对NiFe-LDH的改性方法,这些方法能有效提升反应活性位点数量、增强导电性并促进反应动力学过程。最后,讨论了对NiFe-LDH改性中存在的问题以及对后续研究的展望。     

Defect‐Rich Copper‐doped Ruthenium Hollow Nanoparticles for Efficient Hydrogen Evolution Electrocatalysis in Alkaline Electrolyte

It is of great importance to develop highly e?cient and stable Pt‐free catalysts for electrochemical hydrogen generation from water electrolysis. Here, monodisperse 7.5 nm copper‐doped ruthenium hollow nanoparticles (NPs) with abundant defects and amorphous/crystalline hetero‐phases were prepared and employed as efficient hydrogen evolution electrocatalysts in alkaline electrolyte. Specifically, these NPs only require a low overpotential of 25 mV to achieve a current density of 10 mA cm^?2 in 1.0 M KOH and show acceptable stability after 2000 potential cycles, which represents one of the best Ru‐based electrocatalysts for hydrogen evolution. Mechanism analysis indicates that Cu incorporation can modify the electronic structure of Ru shell, thereby optimizing the energy barrier for water adsorption and dissociation processes or H adsorption/desorption. Cu doping paired with the defect‐rich and highly open hollow structure of the NPs greatly enhances hydrogen evolution activity.     

Three‐Dimensional Branched and Faceted Gold–Ruthenium Nanoparticles: Using Nanostructure to Improve Stability in Oxygen Evolution Electrocatalysis

Achieving stability with highly active Ru nanoparticles for electrocatalysis is a major challenge for the oxygen evolution reaction. As improved stability of Ru catalysts has been shown for bulk surfaces with low‐index facets, there is an opportunity to incorporate these stable facets into Ru nanoparticles. Now, a new solution synthesis is presented in which hexagonal close‐packed structured Ru is grown on Au to form nanoparticles with 3D branches. Exposing low‐index facets on these 3D branches creates stable reaction kinetics to achieve high activity and the highest stability observed for Ru nanoparticle oxygen evolution reaction catalysts. These design principles provide a synthetic strategy to achieve stable and active electrocatalysts.     

Highly Active Electrocatalysis of the Hydrogen Evolution Reaction by Cobalt Phosphide Nanoparticles

Nanoparticles of cobalt phosphide, CoP, have been prepared and evaluated as electrocatalysts for the hydrogen evolution reaction (HER) under strongly acidic conditions (0.50 M H₂SO₄, pH 0.3). Uniform, multi‐faceted CoP nanoparticles were synthesized by reacting Co nanoparticles with trioctylphosphine. Electrodes comprised of CoP nanoparticles on a Ti support (2 mg cm^?2 mass loading) produced a cathodic current density of 20 mA cm^?2 at an overpotential of ?85 mV. The CoP/Ti electrodes were stable over 24 h of sustained hydrogen production in 0.50 M H₂SO₄. The activity was essentially unchanged after 400 cyclic voltammetric sweeps, suggesting long‐term viability under operating conditions. CoP is therefore amongst the most active, acid‐stable, earth‐abundant HER electrocatalysts reported to date.     

Oxygen Evolution Electrocatalysis of a Single MOF‐Derived Composite Nanoparticle on the Tip of a Nanoelectrode

Determination of the intrinsic electrocatalytic activity of nanomaterials by means of macroelectrode techniques is compromised by ensemble and film effects. Here, a unique “particle on a stick” approach is used to grow a single metal–organic framework (MOF; ZIF‐67) nanoparticle on a nanoelectrode surface which is pyrolyzed to generate a cobalt/nitrogen‐doped carbon (CoN/C) composite nanoparticle that exhibits very high catalytic activity towards the oxygen evolution reaction (OER) with a current density of up to 230 mA cm^?2 at 1.77 V (vs. RHE), and a high turnover frequency (TOF) of 29.7 s^?1 at 540 mV overpotential. Identical location transmission electron microscopy (IL‐TEM) analysis substantiates the “self‐sacrificial” template nature of the MOF, while post‐electrocatalysis studies reveal agglomeration of Co centers within the CoN/C composite during the OER. “Single‐entity” electrochemical analysis allows for deriving the intrinsic electrocatalytic activity and furnishes insight into the transient behavior of the electrocatalyst under reaction conditions.     

CoS2 Nanoparticles Embedded in Covalent Organic Polymers as Efficient Electrocatalyst for Oxygen Evolution Reaction with Ultralow Overpotential

Cobalt disulfide (CoS₂) has been explored as attractive electrocatalyst for oxygen evolution reaction (OER). However, bulk CoS₂ sheets have limited catalytic activity due to low exposure of active sites. Herein, through an in-situ vulcanization approach, CoS₂ nanoparticles are embedded into bipyridine-containing covalent organic polymer (BP-COP). The as-prepared nanocomposite CoS₂@BP-COP exhibits high catalytic activity toward OER with an ultra-low overpotential of 270 mV (vs. RHE) at a current density of 10 mA cm⁻², a small Tafel slope of 36 mV dec⁻¹, and an excellent durability for 24 h without decay. The surface of CoS₂ is partially converted into CoOOH to form CoS₂/CoOOH as active sites under OER conditions. CoS₂@BP-COP displays superior OER catalytic activity to CoS₂ nanosheets and commercially available RuO₂ under the same conditions. The outstanding OER performance activity of CoS₂@BP-COP could be attributed to the uniform and small particle sizes of CoS₂/CoOOH distributed in BP-COP.     

MOF‐Derived Double‐Layer Hollow Nanoparticles with Oxygen Generation Ability for Multimodal Imaging‐Guided Sonodynamic Therapy

The high reactive oxygen species (ROS) generation ability and simple construction of sonosensitizer systems remain challenging in sonodynamic therapy against the hypoxic tumor. In this work, we rationally prepared MOF‐derived double‐layer hollow manganese silicate nanoparticle (DHMS) with highly effective ROS yield under ultrasound irradiation for multimodal imaging‐guided sonodynamic therapy (SDT). The presence of Mn in DHMS increased ROS generation efficiency because it could be oxidized by holes to improve the electron–hole separation. Moreover, DHMS could produce oxygen in the tumor microenvironment, which helps overcome the hypoxia of the solid tumor and thus enhance the treatment efficiency. In vivo experiments demonstrated efficient tumor inhibition in DHMS‐mediated SDT guided by ultrasound and magnetic resonance imaging. This work presents a MOF‐derived nanoparticle with sonosensitive and oxygen generating ability, which provides a promising strategy for tumor hypoxia in SDT.     

Molecular Mixed‐Metal Manganese Oxido Cubanes as Precursors to Heterogeneous Oxygen Evolution Catalysts

Well‐defined mixed‐metal [CoMn₃O₄] and [NiMn₃O₄] cubane complexes were synthesized and used as precursors for heterogeneous oxygen evolution reaction (OER) electrocatalysts. The discrete clusters were dropcasted onto glassy carbon (GC) and indium tin oxide (ITO) electrodes, and the OER activities of the resulting films were evaluated. The catalytic surfaces were analyzed by various techniques to gain insight into the structure‐function relationships of the electrocatalysts’ heterometallic composition. Depending on preparation conditions, the Co‐Mn oxide was found to change metal composition during catalysis, while the Ni–Mn oxides maintained the NiMn₃ ratio. XAS studies provided structural insights indicating that the electrocatalysts are different from the molecular precursors, but that the original NiMn₃O₄ cubane‐like geometry was maintained in the absence of thermal treatment ( 2‐Ni ). In contrast, the thermally generated 3‐Ni develops an oxide‐like extended structure. Both 2‐Ni and 3‐Ni undergo structural changes upon electrolysis, but they do not convert into the same material. The observed structural motifs in these heterogeneous electrocatalysts are reminiscent of the biological oxygen‐evolving complex in Photosystem II, including the MMn₃O₄ cubane moiety. The reported studies demonstrate the use of discrete heterometallic oxide clusters as precursors for heterogeneous water oxidation catalysts of novel composition and the distinct behavior of two sets of mixed metal oxides.     

Salen-Based Conjugated Microporous Polymers for Efficient Oxygen Evolution Reaction

Exploring high-performance electrocatalysts, especially non-noble metal electrocatalysts, for the oxygen evolution reaction (OER) is critical to energy storage and conversion. Herein, we report for the first time that conjugated microporous polymers (CMPs) incorporating salen can be used as OER electrocatalysts with outstanding performances. The best OER electrocatalyst (salen-CMP-Fe-3) exhibits a low Tafel slope of 63 mV dec⁻¹ and an overpotential of 238 mV at 10 mA cm⁻². DFT and Grand Canonical Monte Carlo calculations confirmed that the significantly improved electrocatalytic properties can be attributed to the intrinsic catalytic activity of the salen moiety and the enrichment effect of the pore structures. This work demonstrates that salen-based conjugated polymers are a type of metal-coordinated porous polymer that show excellent catalyst performance.     

Cross‐Linked Polyphosphazene Hollow Nanosphere‐Derived N/P‐Doped Porous Carbon with Single Nonprecious Metal Atoms for the Oxygen Reduction Reaction

Heteroatom‐doped polymers or carbon nanospheres have attracted broad research interest. However, rational synthesis of these nanospheres with controllable properties is still a great challenge. Herein, we develop a template‐free approach to construct cross‐linked polyphosphazene nanospheres with tunable hollow structures. As comonomers, hexachlorocyclotriphosphazene provides N and P atoms, tannic acid can coordinate with metal ions, and the replaceable third comonomer can endow the materials with various properties. After carbonization, N/P‐doped mesoporous carbon nanospheres were obtained with small particle size (≈50 nm) and high surface area (411.60 m² g^?1). Structural characterization confirmed uniform dispersion of the single atom transition metal sites (i.e., Co‐N₂P₂) with N and P dual coordination. Electrochemical measurements and theoretical simulations revealed the oxygen reduction reaction performance. This work provides a solution for fabricating diverse heteroatom‐containing polymer nanospheres and their derived single metal atom doped carbon catalysts.     

PBA@POM Hybrids as Efficient Electrocatalysts for the Oxygen Evolution Reaction

To realize the effective conversion of renewable energy through water decomposition, efficient electrocatalysts for the oxygen evolution reaction (OER) are essential. In this article, PBA@POM was successfully prepared with a Prussian blue analogue (PBA) as the initial structure. A facile hydrothermal process is reported for obtaining PBA@POM by etching the cubic PBA with a strong Brønsted acid, H₃PMo₁₂O₄₀ (HPMo). The hollow cube structure not only exposes more active sites but also promotes electron transport, which results in excellent electrocatalytic activity for the OER. Compared with the PBA, which initially simply adhered to POM, the optimum PBA@POM hybrids display remarkably enhanced OER catalytic activity, with an almost constant overpotential of 440 mV at a current density of 10 mA cm^?2 and a small Tafel slope (23.45 mV dec^?1). The facilely prepared PBA@POM with good electrochemical activity and stability promises great potential for the OER.