金属空气电池阴极氧还原催化剂研究进展

随着能源危机加剧和生态环境恶化, 可持续发展能源受到更大的重视. 金属空气电池作为一种绿色能源是具有很大发展潜力的新一代电池. 与传统电池相比, 此类电池有着更高的理论能量密度, 尤其是锂空电池, 能量密度可达3505 Wh/kg, 然而阴极缓慢的氧还原反应成为制约其发展的关键因素之一. 在简要介绍氧还原反应机理基础上, 着重介绍了近年来氧还原催化剂如贵金属及其合金、过渡金属氧化物/硫化物、功能化碳材料和金属氮化物的研究进展, 并根据目前所存在问题指出未来研究方向, 包括深入研究氧还原反应机理, 明确催化剂活性位; 研究催化剂结构等对催化活性的影响, 优化制备条件, 以提高催化活性和稳定性; 根据氧还原机理设计开发新型氧还原催化剂.     

Computational Assistance in the Design of Efficient Oxygen Reduction Reaction Electrocatalysts

Recently, theoretical calculations have played an irreplaceable role in the discovery of electrocatalysts as a relatively time-efficient, cost-effective, and predictable method. More importantly, theoretical calculations can help screen out the best active reaction sites and modulate them accordingly, which is beneficial for the development of efficient catalysts. In this concept, we focus on the important role of theoretical calculations in determining catalytic active sites and understanding reaction mechanisms, emphasizing its importance in assisting the design and synthesis of efficient oxygen reduction reaction catalysts. Finally, we provide an outlook on the challenges and future development trend in this field.     

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.     

A Bifunctional Hybrid Electrocatalyst for Oxygen Reduction and Oxygen Evolution Reactions: Nano-Co3O4-Deposited La0.5Sr0.5MnO3 via Infiltration

For rechargeable metal–air batteries, which are a promising energy storage device for renewable and sustainable energy technologies, the development of cost-effective electrocatalysts with effective bifunctional activity for both oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) has been a challenging task. To realize highly effective ORR and OER electrocatalysts, we present a hybrid catalyst, Co₃O₄-infiltrated La_0.5Sr_0.5MnO_3-δ (LSM@Co₃O₄), synthesized using an electrospray and infiltration technique. This study expands the scope of the infiltration technique by depositing ~18 nm nanoparticles on unprecedented ~70 nm nano-scaffolds. The hybrid LSM@Co₃O₄ catalyst exhibits high catalytic activities for both ORR and OER (~7 times, ~1.5 times, and ~1.6 times higher than LSM, Co₃O₄, and IrO₂, respectively) in terms of onset potential and limiting current density. Moreover, with the LSM@Co₃O₄, the number of electrons transferred reaches four, indicating that the catalyst is effective in the reduction reaction of O₂ via a direct four-electron pathway. The study demonstrates that hybrid catalysts are a promising approach for oxygen electrocatalysts for renewable and sustainable energy devices.     

高性能析氧电催化剂的设计策略

电催化水分解反应是可以实现规模化制取氢气的一种重要绿色无污染的手段,但是其效率极大地受制于阳极析氧反应. 因此,发展廉价、高效的析氧反应催化剂是当下的研究热点. 通过分析决定析氧反应催化活性的因素,本综述总结了低成本、高效、稳定的析氧电催化剂的一些通用设计与制备策略,包括：1）通过电子结构调控、结晶度调控、相调控、缺陷位调控以及自旋态调控提升单个催化活性位点的本征催化活性;2）设计与构筑先进电极结构,以实现活性位点数量最大化,获得大电流下稳定的电极材料. 进而,选取了一些具有代表性的高效析氧催化剂作为例子来阐述这些策略的实用性. 最后,对高效、可在大电流密度下稳定工作的析氧催化剂的理性设计、可控制备和发展方向提出了展望,以期为新型高性能析氧催化剂的设计提供指导.     

A Bifunctional Perovskite Catalyst for Oxygen Reduction and Evolution

La_0.3(Ba_0.5Sr_0.5)_0.7Co_0.8Fe_0.2O_3?δ is a promising bifunctional perovskite catalyst for the oxygen reduction reaction and the oxygen evolution reaction. This catalyst has circa 10 nm‐scale rhombohedral LaCoO₃ cobaltite particles distributed on the surface. The dynamic microstructure phenomena are attributed to the charge imbalance from the replacement of A‐site cations with La³⁺ and local stress on Co‐site sub‐lattice with the cubic perovskite structure.     

金属有机化合物框架材料衍生M-N/C类氧还原电催化剂

过渡金属及氮共掺杂的碳基催化剂(M-N/C)由于具有几乎可以媲美铂的氧还原活性,已成为最为重要的一类非贵金属催化剂,被誉为最有可能在未来应用于燃料电池的一类非贵金属催化剂。金属有机化合物框架材料(MOFs)作为一种新型的结构规整的多孔材料,具有高孔隙度和形貌尺寸可控等特点,成为制备各种高性能掺杂碳基催化剂的良好前驱体,与过渡金属、氮和碳源的复合前驱体相比,以其为原料制得的衍生M-N/C催化剂往往表现出更优越的结构与性能,具备更好的应用前景,相关研究已成为燃料电池电催化领域的热点研究课题。本文系统地介绍了近年来国内外以MOFs为前驱体制备M-N/C催化剂的相关研究工作,包括:MOFs 衍生碳催化剂的制备技术,提升MOFs衍生碳催化剂结构及性能的研究以及这类催化剂表征技术的研究工作。总结和讨论了MOFs衍生M-N/C催化剂尚存的若干重要问题并提出了解决问题的可能举措,对这类催化剂的发展及应用进行了展望。     

Carbon Nanodots as Electrocatalysts towards the Oxygen Reduction Reaction

Electrocatalysts perform a key role in increasing efficiency of the oxygen reduction reaction (ORR) and as a result, efforts have been made by the scientific community to develop novel and cheap materials that have the capability to exhibit low ORR overpotentials and allow the reaction to occur via a 4 electron pathway, thereby mimicking as close as possible to traditionally utilised platinum. In that context, two different types of carbon nanodots (CNDs) with amide (CND‐CONH₂) and carboxylic (CND‐COOH) surface groups, have herein been fabricated and shown to exhibit excellent electrocatalytic activity towards the ORR in acid and basic media (0.1 M H₂SO₄ and 0.1 M KOH). CND surface modified carbon screen‐printed electrodes allow for a facile electrode modification and enabling the study of the CNDs electrocatalytic activity towards the ORR. CND‐COOH modified SPEs are found to exhibit improved ORR peak current and reduced overpotential by 21.9 % and 26.3 %, respectively compared to bare/unmodified SPEs. Additionally, 424 μg cm⁻² CND‐COOH modified SPEs in oxygenated 0.1 M KOH are found to facilitate the ORR via a near optimal 4 (3.8) electron ORR pathway. The CNDs also exhibited excellent long‐term stability and tolerance with no degradation being observed in the achievable current with the ORR current returning to the baseline level within 100 seconds of exposure to a 1.5 M solution of methanol. In summary, the CND‐COOH could be utilised as a cathodic electrode for PEMFCs offering greater stability than a commercial Pt electrode.     

Hollow-Structure Pt-Ni Nanoparticle Electrocatalysts for Oxygen Reduction Reaction

An electrocatalyst with high oxygen reduction reaction (ORR) activity and high stability during start–stop operation is necessary. In this paper, hollow-structure Pt-Ni electrocatalysts are investigated as ORR catalysts. After synthesis via sacrificial SiO₂ template method, the electrocatalyst exhibits much higher specific activity (1.88 mA/cm²) than a commercial Pt/C catalyst. The mass activity (0.49 A/mg) is 7 times higher than the commercial Pt/C catalyst. The kinetics of the ORR is evaluated using Tafel and K-L plots. It also exhibits a higher durability than commercial Pt/C catalyst during accelerated durability test (ADT). Moreover, the electrocatalyst shows good resistance against accelerated durability test for start–stop, the specific activity and mass activity drops 34.6% and 40.8%, respectively, far better than the commercial catalyst.     

三元合金氧还原电催化剂

质子交换膜燃料电池作为重要的电化学能源转换装置,在提高能量转换效率、减少环境污染等方面具有诱人的前景.然而,阴极氧还原过电位较大、活性较低、稳定性差,且铂基催化剂昂贵,使该燃料电池难以商业化.纳米结构电催化剂的发展有望解决此难题。对纳米合金电催化剂其组分和结构的设计是开发高活性、高稳定性和低成本的燃料电池电催化剂的重要因素.本文综述了近期由分子设计和热化学控制处理法制备的三元纳米合金电催化剂对燃料电池氧还原反应催化性能的最新进展.该方法可控制纳米合金的尺寸、组成以及二元和三元纳米催化剂的合金化程度.以高活性的三元纳米合金催化剂PtNiCo/C为例,综述了在设计燃料电池电催化剂时结构和组成的纳米级调优的重要性.PtNiCo/C电催化剂的质量比活性远高于其二元合金催化剂和Pt/C商业电催化剂.三元电催化剂的催化活性可通过控制其组成来调节.文章还讨论了三元纳米合金催化剂的结构及其协同效应对增强其电催化性能的影响.     

NiO@rGO负载钯、银纳米粒子用作氧还原催化剂

为了促进燃料电池的广泛应用,必须研发一种高效、经济的氧还原（ORR）催化剂材料替代目前使用的昂贵的Pt基催化剂. 本文合成了NiO@rGO、Pd-NiO@rGO和Ag-NiO@rGO三种催化剂材料,并对其ORR催化性能进行了比较研究. 结果表明,三种材料均具有催化ORR的能力,但与NiO@rGO相比,Pd-NiO@rGO和Ag-NiO@rGO展示了更加优异的性能,主要表现在其4电子转移ORR过程、起始电位增加,中间产物的产率降低和稳定性提高. 其中,Pd-NiO@rGO作为ORR催化剂的性能最好.     

A Bifunctional Electrocatalyst for Oxygen Evolution and Oxygen Reduction Reactions in Water

Oxygen reduction and water oxidation are two key processes in fuel cell applications. The oxidation of water to dioxygen is a 4 H⁺/4 e^? process, while oxygen can be fully reduced to water by a 4 e^?/4 H⁺ process or partially reduced by fewer electrons to reactive oxygen species such as H₂O₂ and O₂^?. We demonstrate that a novel manganese corrole complex behaves as a bifunctional catalyst for both the electrocatalytic generation of dioxygen as well as the reduction of dioxygen in aqueous media. Furthermore, our combined kinetic, spectroscopic, and electrochemical study of manganese corroles adsorbed on different electrode materials (down to a submolecular level) reveals mechanistic details of the oxygen evolution and reduction processes.     

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.     

A Permselective CeOx Coating To Improve the Stability of Oxygen Evolution Electrocatalysts

Highly active NiFeO_x electrocatalysts for the oxygen evolution reaction (OER) suffer gradual deactivation with time owing to the loss of Fe species from the active sites into solution during catalysis. The anodic deposition of a CeO_x layer prevents the loss of such Fe species from the OER catalysts, achieving a highly stable performance. The CeO_x layer does not affect the OER activity of the catalyst underneath but exhibits unique permselectivity, allowing the permeation of OH^? and O₂ through while preventing the diffusion of redox ions through the layer to function as a selective O₂‐evolving electrode. The use of such a permselective protective layer provides a new strategy for improving the durability of electrocatalysts.     

高结晶度硼酸镍纳米棒的制备及其电催化析氧性能研究

氢能被视为21世纪最具发展潜力的能源. 电解水制氢具有诸多优点,如原料来源广泛、操作简便、产品纯度高、无污染,已成为最具有应用前景的方法之一,但其阳极氧析出反应动力学缓慢,严重制约电解水制氢的效率. 因此,发展氧析出电催化剂尤为重要. 本文利用高温煅烧法制备了硼酸镍纳米棒,长度约为2 μm,直径约为200 nm. 与文献报道的低结晶度或无定型硼酸盐析氧催化剂不同,硼酸镍纳米棒的结晶度较高,并且具有较好的OER催化活性和稳定性. 其催化活性可以通过与其他导电材料复合或进一步减小其尺寸等方式提升.     

Covalent Organic Frameworks Based Single-site Electrocatalysts for Oxygen Reduction Reaction

Single site catalysts(SSCs) are a new type of heterogeneous catalysts formed by isolated metal atoms supported on kinds of substrates. SSCs have shown great potential for energy conversion and storage in recent years, especially for oxygen reduction reactions(ORR). Typically, SSCs are confined on the substrate by strong chemical interactions, such as coordination bonds. Therefore, the surface chemical environment and porous properties of the supports are crucial to the performance of SSCs. In recent years, COFs have become excellent candidates for preparing SSCs as they can precisely assemble monomers into highly ordered crystalline porous materials with a fine structure and definite components. In this review, we not only summarize the characteristics and advantages of COFs based SSCs, but also highlight the applications of COFs constructed from different single active sites for ORR in recent years. Finally, challenges in practical application, feasible strategies and perspectives are proposed for the of COFs based SSCs.     

Bioinspired Transition-Metal Complexes as Electrocatalysts for the Oxygen Reduction Reaction

The oxygen reduction reaction (ORR) is one of the most important reactions in life processes and energy conversion systems. To alleviate global warming and the energy crisis, the development of high-performance electrocatalysts for the ORR for application in energy conversion and storage devices such as metal–air batteries and fuel cells is highly desirable. Inspired by the biological oxygen activation/reduction process associated with heme- and multicopper-containing metalloenzymes, iron and copper-based transition-metal complexes have been extensively explored as ORR electrocatalysts. Herein, an outline into recent progress on non-precious-metal electrocatalysts for the ORR is provided; these electrocatalysts do not require pyrolysis treatment, which is regarded as desirable from the viewpoint of bioinspired molecular catalyst design, focusing on iron/cobalt macrocycles (porphyrins, phthalocyanines, and corroles) and copper complexes in which the ORR activity is tuned by ligand variation/substitution, the method of catalyst immobilization, and the underlying supporting materials. Current challenges and exciting imminent developments in bioinspired ORR electrocatalysts are summarized and proposed.     

Evaluation of Perovskites as Electrocatalysts for the Oxygen Evolution Reaction

The oxygen evolution reaction (OER) is an enabling process for technologies in the area of energy conversion and storage, but its slow kinetics limits its efficiency. We performed an electrochemical evaluation of 14 different perovskites of variable composition and stoichiometry as OER electrocatalysts in alkaline media. We particularly focused on improved methods for a reliable comparison of catalyst activity. From initial electrochemical results we selected the most active samples for further optimization of electrode preparation and testing. An inverted cell configuration facilitated gas bubble detachment and thus minimized blockage of the active surface area. We describe parameters, such as the presence of specific cations, stoichiometry, and conductivity, that are important for obtaining electroactive perovskites for OER. Conductive additives enhanced the current and decreased the apparent overpotential of OER for one of the most active samples (La_0.58Sr_0.4Fe_0.8Co_0.2O₃).     

燃料电池非铂基氧还原电催化剂的最新研究进展

目前,燃料电池中广泛使用的Pt基阴极催化剂价格昂贵、资源缺乏,且易中毒,故急需开发廉价、耐用、高效和高耐醇的非铂基阴极氧还原催化剂. 本文阐述了国内外在非铂氧还原催化剂方面的研究,并着重介绍了作者课题组的最新研究进展. 主要集中在非贵金属（Fe）负载和杂原子（F）掺杂的非金属催化剂,力求原料廉价并可提高催化剂的催化活性、稳定性、抗毒化能力,实现较高的性价比. 同时通过理论计算解释了氟单掺杂和氮氟共掺杂高效性的根源,为设计高效催化剂提供了有力的理论支持.     

Effects of the Pt Shell Thickness on the Oxygen Reduction Reaction on a Well-Defined Pd@Pt Core-Shell Model Surface

The effect of the Pt shell thickness on the oxygen reduction reaction (ORR) of a Pd@Pt core-shell catalyst was studied using surface science technics and computational approaches. We found Pt shells on Pd rods to be negatively charged because of charge transfer from the Pd substrate when the shell thicknesses were 0.5 or 1 monolayer (ML). The activities of the ORR of the model surface with a Pt shell of 0.5 or 1 ML were similar and more than twice the activities of a Pt/C or Pt rod. The relationship between the ORR activity and the thickness of the Pt shell was the exact opposite of the relationship between the Pt binding energy and the Pt shell thickness. The indication was that more negatively charged Pt had higher ORR activity. Density functional theory calculations confirmed that a single layer of Pt atoms located on Pd was negatively charged compared to pure Pt and resulted in a lower barrier to the rate-limiting step of the ORR.