Self-Assembled Two-Dimensional NiO/CeO2 Heterostructure Rich in Oxygen Vacancies as Efficient Bifunctional Electrocatalyst for Alkaline Hydrogen Evolution and Oxygen Evolution

The development of high-efficiency bifunctional electrocatalysts toward the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) in alkaline surroundings is essential and challenging for the large-scale generation of clean hydrogen. Herein, a novel self-assembled two-dimensional (2 D) NiO/CeO₂ heterostructure (HS) consisting of NiO and CeO₂ nanocrystals is prepared through a facile two-step approach, and utilized as an enhanced bifunctional electrocatalyst for the HER and OER under alkaline conditions. It is concluded that this 2 D NiO/CeO₂ HS, rich in oxygen vacancies, demonstrates attractive electrocatalytic properties for both the HER and OER in 1 m KOH, including low onset overpotential (η₁), η₁₀ and Tafel slope, excellent durability, as well as large active surface area. Therefore, the self-assembled 2 D NiO/CeO₂ HS is believed to be an efficient bifunctional electrocatalyst toward the HER and OER.     

Two-dimensional Metal-Organic Frameworks as Electrocatalysts for Oxygen Evolution Reaction

Oxygen evolution reaction(OER) plays an important role in many electrochemical systems. However, its sluggish kinetics severely limits the development of next-generation energy technologies. Recently, two-dimensional(2D) metal-organic frameworks(MOFs) have attracted much attention as a class of promising electrocatalysts. Their diverse components and tunable structures provide a new platform to design and explore ideal electrocatalysts. The ultrathin characteristics including high specific surface area, abundant exposed metal sites and fast electronic transfer further promote the electrocatalytic performance of 2D MOFs. Therefore, many attempts have been made in synthesizing 2D MOF-based electrocatalysts in recent years. This review focuses on the strategies to fabricate 2D MOFs with high electrocatalytic performances for OER. The discussion on challenge and development of their electrocatalytic application is also presented.     

Theoretical Investigation on the Hydrogen Evolution,Oxygen Evolution,and Oxygen Reduction Reactions Performances of Two-Dimensional Metal-Organic Frameworks Fe3(C2X)12 (X = NH,O, S)

Two-dimensional metal-organic frameworks (2D MOFs) inherently consisting of metal entities and ligands are promising single-atom catalysts (SACs) for electrocatalytic chemical reactions. Three 2D Fe-MOFs with NH, O, and S ligands were designed using density functional theory calculations, and their feasibility as SACs for hydrogen evolution reaction (HER), oxygen evolution reaction (OER), and oxygen reduction reaction (ORR) was investigated. The NH, O, and S ligands can be used to control electronic structures and catalysis performance in 2D Fe-MOF monolayers by tuning charge redistribution. The results confirm the Sabatier principle, which states that an ideal catalyst should provide reasonable adsorption energies for all reaction species. The 2D Fe-MOF nanomaterials may render highly-efficient HER, OER, and ORR by tuning the ligands. Therefore, we believe that this study will serve as a guide for developing of 2D MOF-based SACs for water splitting, fuel cells, and metal-air batteries.     

Electrocatalysts Based on Transition Metal Borides and Borates for the Oxygen Evolution Reaction

Electrochemical water splitting is a clean and sustainable process for hydrogen production on a large scale as the electrical power required can be obtained from various renewable energy resources. The key challenge in electrochemical water splitting process is to develop low-cost electrocatalysts with high catalytic activity for the hydrogen evolution reaction (HER) on the cathode and the oxygen evolution reaction (OER) on the anode. OER is the most important half-reaction involved in water splitting, which has been extensively studied since the last century and a large amount of electrocatalysts including noble and non-noble metal-based materials have been developed. Among them, transition metal borides and borates (TMBs)-based compounds with various structures have attracted increasing attention owing to their excellent OER performance. In recent years, many efforts have been devoted to exploring the OER mechanism of TMBs and to improving the OER activity and stability of TMBs. In this review, recent research progress made in TMBs as efficient electrocatalysts for OER is summarized. The chemical properties, synthetic methodologies, catalytic performance evaluation, and improvement strategy of TMBs as OER electrocatalysts are discussed. The electrochemistry fundamentals of OER are first introduced in brief, followed by a summary of the preparation and performance of TMBs-based OER electrocatalysts. Finally, current challenges and future directions for TMBs-based OER electrocatalysts are discussed.     

基于四硫富瓦烯的无金属共价有机框架材料用于高效电催化析氧反应

共价有机框架(COFs)在电催化析氧反应(OER)中的应用得到了广泛的关注。然而,大多数无金属共价有机框架(COFs)的导电性较差,不利于OER反应。四硫富瓦烯(TTF)是一种良好的电子供体,具有快速的电子转移能力,将TTF整合到共价有机框架骨架中将有助于电子的转移。在此,我们报道了一种基于四硫富瓦烯的二维无金属共价有机框架材料,JUC-630。与不含四硫富瓦烯的同类材料(Etta-Td COF)相比,JUC-630具有较低的过电位(400 mV)和塔菲尔斜率(104 mV∙dec⁻¹)。本研究提出了合理设计功能基元的策略,这有助于大大提高COF材料的OER催化活性。     

Bifunctional Electrocatalyst with 0D/2D Heterostructure for Highly Efficient Hydrogen and Oxygen Generation

A novel MoS₂ quantum dots/CoSe₂ nanosheet (MoS₂ QDs/CoSe₂) hybrid with 0D/2D heterostructure has been developed. The CoSe₂ nanosheets (NSs) enable an excellent oxygen evolution reaction (OER) activity with increasing vacancy configuration on one hand, while the MoS₂ QDs serve as an eminent hydrogen evolution reaction (HER) catalyst on the other. By integrating MoS₂ QDs and CoSe₂ NSs, the hybrid exhibits excellent electrocatalytic performances in HER and OER. The unique 0D/2D hetero‐interface increases the exposed active sites and facilitates electron transfer, thereby boosting the electrocatalytic activity. Relatively low overpotentials of 82 mV and 280 mV are required to drive the current density of 10 mA/cm² for HER and OER, with corresponding Tafel slopes of 69 and 75 mV/dec, respectively. As such, this work provides an efficient yet simple approach to construct bifunctional electrocatalysts with enhanced activity and stability.     

Transition metal tellurides as emerging catalysts for electrochemical water splitting

Renewable energy powered electrochemical water splitting has been recognized as a sustainable and environmentally-friendly way to produce green hydrogen, which is an important vector to decarbonize the transport sector and hard-to-abate industry, able to contribute to achieving global carbon neutrality. For large-scale deployment of water electrolyzers, it is essential to develop efficient and durable electrocatalysts—one of key components determining the electrochemical performance, based on cheap and earth-abundant materials. To this end, transition metal tellurides (TMTs) have recently emerged as a promising alternative to the conventional platinum group metals for both hydrogen evolution reaction (HER) and oxygen evolution reaction (OER). This review article provides a brief account of the latest development in TMT-based HER and OER catalysts, with a focus on various strategies developed to improve the catalytic performance, such as nanostructure engineering, composition engineering, and heterostructuring/hybridization. Perspectives of future research on TMT-based catalysts are also shortly outlined.     

非晶非贵金属催化剂的研究进展及展望

近年来电解水产氢作为一种具有前景的制备及储存可再生能源的方法受到了各界的广泛关注.在此过程中,电解水催化剂是提高能源转换效率的关键.优秀的催化剂应具备高催化活性、高稳定性、低成本以及可大规模生产等性质.科研工作者对电解水的两部分反应,即析氢反应以及析氧反应均进行了广泛及深入的研究.目前,贵金属催化剂,如铂基、钌基催化剂的催化活性要高于其他元素催化剂,但由于其价格昂贵,储量较少使得贵金属催化剂无法得到大规模应用,因此发展非贵金属催化剂对绿色能源的发展具有重要意义.一般而言,催化剂的结晶度越高,其催化活性越好,而近年来非晶催化剂以其更高的催化活性位密度也越来越受到人们的重视.同时,非晶催化剂的成分更加灵活,相比晶体催化剂来说非晶催化剂可以在更大范围内对成分进行调节.此外,非晶催化剂的制备通常都在较为温和的反应条件下进行,这也能够降低生成成本,促进其工业化发展.在这篇综述里我们介绍了电解水反应的基本原理,总结了近期非晶析氢、析氧以及双功能催化剂的研究进展.并随后探讨了电解水反应目前的难点并对非晶催化剂的制备进行了展望.     

Phosphorene-Based Electrocatalysts

Phosphorene, generally defined as two-dimensional (2D) black phosphorus (BP) with monolayered or few-layered structure, has emerged as a promising member of the family of 2D materials. Since its discovery in 2014, extensive research has been focused on broadening its applications, covering the biological, photoelectric, and electrochemical fields, owing to the unique physicochemical and structural properties. As a single-elemental material, phosphorene has demonstrated its applicability for the preparation of efficient electrocatalysts for hydrogen evolution reaction (HER), oxygen evolution reaction (OER), nitrogen reduction reaction (NRR), and other electrocatalytic applications. In this Minireview, a summary of the very recent research progresses of phosphorene in electrocatalysis is offered, with a special focus on the effective synthetic strategies towards performance improvement. In the concluding section, challenges and perspectives are also discussed.     

二维材料用于电催化析氢的研究进展

电催化水分解因其丰富的原料来源和环境友好被认为是一种有前途的制氢技术. 开发用于电催化析氢反应的高效电催化剂是迫切需要的. 随着石墨烯的兴起, 二维(2D)材料因其独特的物理、 化学和电子特性, 已逐渐成为水电解的潜在候选材料. 本文介绍了二维材料用于电化学水分解产生氢气的最新进展, 概括了二维材料的合成方法, 总结了改善二维材料电化学析氢性能的策略, 讨论了该领域面临的挑战和未来的发展机遇.     

基于醌基的共价有机框架用于电催化析氧反应

将蒽醌作为构筑单元设计合成了醌基功能化的新型2,6-二氨基蒽醌共价有机框架(DAAQ-COF). 粉末X射线衍射、 氮气吸附-脱附、 红外和热重等分析结果表明, DAAQ-COF具有高的结晶度和比表面积(577 m²/g). 此外, 醌基功能化的无金属DAAQ-COF显示出高的析氧反应(OER)活性(10 mA/cm²下, 过电位389 mV, Tafel斜率135 mV/dec). 这源于引入的醌基基团有效改变了COF框架的电子结构和化学特性, 加上COF材料本身的高结晶度和比表面积, 使得反应物能更有效地与活性位点接触, 从而促进OER进程. 这些结果表明合理地设计功能化的COF材料能够进一步推动此类材料在电催化领域的应用.     

Carbon‐Based Metal‐Free Catalysts for Electrocatalysis beyond the ORR

Besides their use in fuel cells for energy conversion through the oxygen reduction reaction (ORR), carbon‐based metal‐free catalysts have also been demonstrated to be promising alternatives to noble‐metal/metal oxide catalysts for the oxygen evolution reaction (OER) in metal–air batteries for energy storage and for the splitting of water to produce hydrogen fuels through the hydrogen evolution reaction (HER). This Review focuses on recent progress in the development of carbon‐based metal‐free catalysts for the OER and HER, along with challenges and perspectives in the emerging field of metal‐free electrocatalysis.     

High-performance electrocatalyst of vanadium-iron bimetal organic framework arrays on nickel foam for overall water splitting

The development of active,low-cost and durable bifunctional electrocatalysts toward both oxygen evolution reaction(OER) and hydro gen evolution react ion(HER) a re important for overall water splitting.Here,well-defined arrays of vanadium-iron bimetal organic frameworks(VFe-MOF) with controllable stoichiometry have been successfully prepared on nickel foam(NF).The as-fabricated VFe-MOF@NF electrode exhibits excellent electrocatalytic activity and durability for OER and HER in alkaline medium.The material's overpotentials of 10 mA/cm~2 are 246 mV for OER and 147 mV for HER,respectively.The electrolyzer made from the VFe-MOF@NF electrodes as both the cathode and anode in 1 mol/L KOH needs only a voltage of 1.61 V to reach a current density of 10 mA/cm~2.The superior performance of VFeMOF@NF can be attributed to the morphological control and electronic regulation of the bimetals,that is,1) the exposure of the active sites at electrocatalyst/electrolyte interfaces due to the array structure;2)the synergistic effect of vanadium and iron metals on electro-catalyzing the overall water splitting.     

Polyoxometalate-Based Compounds for Photo- and Electrocatalytic Applications

Photo/electrocatalysis of water (H₂O) splitting and CO₂ reduction reactions is a promising strategy to alleviate the energy crisis and excessive CO₂ emissions. For the hydrogen evolution reaction (HER), oxygen evolution reaction (OER), and CO₂ reduction reaction (CO₂RR) involved, the development of effective photo/electrocatalysts is critical to reduce the activation energy and accelerate the sluggish dynamics. Polyoxometalate (POM)-based compounds with tunable compositions and diverse structures are emerging as unique photo/electrocatalysts for these reactions as they offer unparalleled advantages such as outstanding solution and redox stability, quasi-semiconductor behaviour, etc. This Minireview provides a basic introduction related to photo/electrocatalytic HER, OER and CO₂RR, followed by the classification of pristine POM-based compounds toward different catalytic reactions. Recent breakthroughs in engineering POM-based compounds as efficient photo/electrocatalysts are highlighted. Finally, the advantages, challenges, strategies and outlooks of POM-based compounds on improving photo/electrocatalytic performance are discussed.     

导电MOFs在能源转化中的应用

可再生能源供应方案包括析氢反应(HER)、析氧反应(OER)、氧还原反应(ORR)和二氧化碳还原反应(CO2RR)等多种反应,电催化剂对这些反应至关重要。到目前为止,已有一系列导电MOFs作为与能源相关电催化电极材料的报道。本文从提高MOFs导电能力和对产物的选择性、增强MOFs的化学稳定性及增加MOFs的反应活性位点等方面介绍了导电MOFs作为电催化剂的设计策略,重点综述了其在能源转化涉及的HER、OER、ORR以及CO2RR方面的应用,并从材料制备和应用需求角度出发, 对高性能导电MOFs材料在电催化领域所面临的挑战和前景进行了展望。     

NiS-Ni3S2树状异质结阵列在析氧反应中的应用

在过去的几十年里,数以万计化石能源的开发和利用导致了一系列的环境问题,例如温室效应和水污染等。许多应对的策略被提出以应对环境问题,可再生氢气是其中一个最为瞩目的能源。而在其中,电解水是为了获得可在生氢气最为环保的方案。在阳极发生反应过于低效则限制着这项技术的发展,所以研究开发高效的阳极电催化剂变得尤为重要。在本文中,我们通过一步水热法合成了一种直接生长在泡沫镍基地的NiS-Ni₃S₂树状异质结阵列。这个材料在实际电解水的阳极反应中表现出巨大的潜能,表现出高效的电催化性能和超强的稳定性能。NiS-Ni₃S₂树状异质结阵列比纳米棒状Ni₃S₂表现出更好的性能。因为其拥有更高的比表面积和NiS-Ni₃S₂之间协同效应展现。NiS-Ni₃S₂树状异质结阵列的高性能也可能是因为其紧密地与泡沫镍基地连接,拥有较好的电子传输路径。同时,在反应的过程中,一些羟基氢氧化镍的产生也有利于催化效果的提升。毫无疑问,NiS-Ni₃S₂树状异质结阵列作为电解水的阳极催化剂拥有极大的前景。     

Fe‐Doped Ni3C Nanodots in N‐Doped Carbon Nanosheets for Efficient Hydrogen‐Evolution and Oxygen‐Evolution Electrocatalysis

Uniform Ni₃C nanodots dispersed in ultrathin N‐doped carbon nanosheets were successfully prepared by carburization of the two dimensional (2D) nickel cyanide coordination polymer precursors. The Ni₃C based nanosheets have lateral length of about 200 nm and thickness of 10 nm. When doped with Fe, the Ni₃C based nanosheets exhibited outstanding electrocatalytic properties for both the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER). For example, 2 at % Fe (atomic percent) doped Ni₃C nanosheets depict a low overpotential (292 mV) and a small Tafel slope (41.3 mV dec⁻¹) for HER in KOH solution. An outstanding OER catalytic property is also achieved with a low overpotential of 275 mV and a small Tafel slope of 62 mV dec⁻¹ in KOH solution. Such nanodot‐incorporated 2D hybrid structures can serve as an efficient bifunctional electrocatalyst for overall water splitting.     

提升二维材料的电催化析氢和光催化析氢性能的策略

世界能源危机问题和环境问题日益突出,寻找低廉、易得且能够替代化石的清洁能源是目前研究的热点.氢气具有可再生性、安全、高能量密度、环境友好型等优点,因而成为替代化石燃料的首选.在众多途径中,电催化产氢和光催化产氢是目前应用较广且比较成熟的方法,其工艺过程简单、无污染,但由于效率较低或生产成本较高等因素,其大规模应用受到一...     

三维百合花状的CoNi2S4作为先进的双功能电催化剂用于氢析出和氧析出反应

为简化电解水催化剂的合成过程和优化电解水操作系统, 双功能电解水催化剂的研究, 特别是在碱性条件下同时具有优异催化氢析出和氧析出反应性能的双功能电催化剂的研究尤为重要. 其中, 过渡金属硫化物, 特别是 CoNi 硫化物, 被报道有与氢化酶类似的催化活性中心, 从而具有优异的催化氢析出和催化氧析出反应性能. 虽然有关对过渡金属硫化物的研究很多, 但主要集中在具有一维纳米线和二维纳米片形貌结构的过渡金属硫化物. 不幸的是, 这些形貌结构的过渡金属硫化物在电催化过程中容易聚集和受限于电荷传输能力. 三维纳米结构的材料具有较大的比表面积以分布更多的活性位点和拥有良好的电子传输能力, 所以, 开发三维纳米结构的过渡金属硫化物材料可能是改进其催化电解水性能的一个好途径. 本文采用简单的两步水热法, 通过硫化合成的 CoNi 前体得到了长于泡沫镍上的三维百合花状的 CoNi2S4(Co-Ni2S4/Ni). 它只需要 54 mV 的过电位即可获得 10 mA cm-2的催化氢析出反应电流, 是最好的碱性催化氢析出反应电极材料之一. 它在驱动 100 mA cm-2的催化氧析出反应电流时也只需要 328 mV 的过电位. 另外, 把 CoNi2S4/Ni 分别作为阴极和阳极组装成双电极碱性水电解槽时, 它只需要 1.56 V 的电压即可获取 10 mA cm-2的催化全电解水电流并具有良好的催化全电解水稳定性.扫描电子显微镜、透射电子显微镜和 N2吸脱附曲线测试结果表明, 该三维百合花状的 CoNi2S4/Ni 的表面粗糙度高和拥有多孔特性. 多孔结构的 CoNi2S4/Ni 可提供更多可接触的催化活性位点, 也有利于催化过程中的电解质和生成的气体的扩散与传递. 交流阻抗图谱测试结果表明, CoNi2S4/Ni 具有良好的电子传输能力. 另外, 不同于前期对尖晶石结构的硫化物 AB2S4的研究结果, XPS 结果表明, CoNi2S4/Ni 中含有 Niб+和 Sб-活性物种, 表明 CoNi2S4具有与活性氢化酶类似的活 性中心. Niδ+和 Sδ-可分别作为氢氧根和质子的接收体, 协助促进吸附的水分子的分离, 从而提高材料的催化性能. 所以, Niδ+和 Sδ-活性物种的出现, 大比表面积的三维百合花状多孔结构和良好的电荷传输能力等特性集合于 CoNi2S4/Ni 上使得CoNi2S4/Ni 具有优异的催化氢析出和催化氧析出反应性能.     

Cobaloxime-Integrated Covalent Organic Frameworks for Photocatalytic Hydrogen Evolution Coupled with Alcohol Oxidation

We report an azide-functionalized cobaloxime proton-reduction catalyst covalently tethered into the Wurster-type covalent organic frameworks (COFs). The cobaloxime-modified COF photocatalysts exhibit enhanced photocatalytic activity for hydrogen evolution reaction (HER) in alcohol-containing solution with no presence of a typical sacrificial agent. The best performing cobaloxime-modified COF hybrid catalyzes hydrogen production with an average HER rate up to 38 μmol h⁻¹ in ethanol/phosphate buffer solution under 4 h illumination. Ultrafast transient optical spectroscopy characterizations and charge carrier analysis reveal that the alcohol contents functioning as hole scavengers could be oxidized by the photogenerated holes of COFs to form aldehydes and protons. The consumption of the photogenerated holes thus suppresses exciton recombination of COFs and improves the ratio of free electrons that were effectively utilized to drive catalytic reaction for HER. This work demonstrates a great potential of COF-catalyzed HER using alcohol solvents as hole scavengers and provides an example toward realizing the accessibility to the scope of reaction conditions and a greener route for energy conversion.