氢气是一种可持续性的清洁能源，不排放有毒气体，并可为交通、发电、金属制造等多个行业增加价值。存储和运输氢气的技术弥合了可持续能源生产与燃料使用之间的鸿沟，效率更高的氢气输送系统能够为固定电源、移动电源、移动汽车等应用带来很多好处，因此也成为了氢经济中不可或缺的部分。但是，传统的储氢与运输氢气的技术非常昂贵，且容易使氢气被污染。因此，研究人员一直在寻找可靠、低成本且简单的替代技术。

Hydrogen is a sustainable source of clean energy that avoids toxic emissions and can add value to multiple sectors in the economy including transportation, power generation, metals manufacturing, among others.  Technologies for storing and transporting hydrogen bridge the gap between sustainable energy production and fuel use, and therefore are an essential component of a viable hydrogen economy. But traditional means of storage and transportation are expensive and susceptible to contamination. As a result, researchers are searching for alternative techniques that are reliable, low-cost and simple. More-efficient hydrogen delivery systems would benefit many applications such as stationary power, portable power, and mobile vehicle industries.

氮化硼2D基底（图片来源：劳伦斯伯克利国家实验室）

现在，据《美国国家科学院院刊》杂志报道，美国劳伦斯伯克利国家实验室（Lawrence Berkeley National Laboratory）的一组研究人员设计并合成了一种高效的材料，可以加速从醇中提取氢。该材料是一种催化剂，由固定在2D基底上的微小镍金属簇构成。该研究小组发现，此种催化剂可以高效地加速从液体化学载体中移除氢原子的反应，而且该材料非常坚固，由储量丰富的金属，而不是由现有的贵金属制成，将能够有助于使氢成为各种应用的能源。

Now, as reported in the journal Proceedings of the National Academy of Sciences, researchers have designed and synthesized an effective material for speeding up one of the limiting steps in extracting hydrogen from alcohols. The material, a catalyst, is made from tiny clusters of nickel metal anchored on a 2D substrate. The team led by researchers at Lawrence Berkeley National Laboratory’s (Berkeley Lab) Molecular Foundry found that the catalyst could cleanly and efficiently accelerate the reaction that removes hydrogen atoms from a liquid chemical carrier. The material is robust and made from earth-abundant metals rather than existing options made from precious metals, and will help make hydrogen a viable energy source for a wide range of applications.

"我们在这里提出的不仅仅是一种比我们测试的其他镍催化剂具有更高活性的催化剂，用于一种重要的可再生能源燃料，而且还提出了一个更广泛的战略，朝着在广泛的反应中使用经济实惠的金属，"领导这项工作的分子铸造厂无机纳米结构设施主任Jeff Urban说。该研究是氢材料高级研究联盟（HyMARC）的一部分，该联盟由美国能源部能源效率和可再生能源办公室氢气和燃料电池技术办公室（EERE）资助。通过这一努力，五个国家实验室致力于解决阻碍固体储氢材料发展的科学空白。这项工作的成果将直接纳入EERE的H2@Scale愿景，即在经济的多个部门进行负担得起的氢气生产、储存、分配和利用。

“We present here not merely a catalyst with higher activity than other nickel catalysts that we tested, for an important renewable energy fuel, but also a broader strategy toward using affordable metals in a broad range of reactions,” said Jeff Urban, the Inorganic Nanostructures Facility director at the Molecular Foundry who led the work. The research is part of the Hydrogen Materials Advanced Research Consortium (HyMARC), a consortium funded by the U.S. Department of Energy’s Office of Energy Efficiency and Renewable Energy Hydrogen and Fuel Cell Technologies Office (EERE). Through this effort, five national laboratories work towards the goal to address the scientific gaps blocking the advancement of solid hydrogen storage materials. Outputs from this work will directly feed into EERE’s H2@Scale vision for affordable hydrogen production, storage, distribution and utilization across multiple sectors in the economy.

此类作为催化剂的化合物通常用于加速化学反应的速率，而化合物自身并不会被消耗，而是能够将一个特定的分子保持在一个稳定的位置，或者充当一个中介，让某个重要的化学步骤能够顺利完成。至于能够从液体载体产生氢气的化学反应而言，最高效的催化剂一般都由昂贵金属制成。不过，此类催化剂通常成本高、储量不丰富，而且容易被污染。而由普通金属制成的较便宜的催化剂往往效率较低且稳定性较差，活性受到限制，也限制其在制氢工业中得到实际应用。

Chemical compounds that act as catalysts like the one developed by Urban and his team are commonly used to increase the rate of a chemical reaction without the compound itself being consumed—they might hold a particular molecule in a stable position, or serve as an intermediary that allows an important step to be reliably to completed. For the chemical reaction that produces hydrogen from liquid carriers, the most effective catalysts are made from precious metals. However, those catalysts are associated with high costs and low abundance, and are susceptible to contamination. Other less expensive catalysts, made from more common metals, tend to be less effective and less stable, which limits their activity and their practical deployment into hydrogen production industries.

为了改进此类由储量丰富的金属制成的催化剂，研究人员改变了策略，专注于微小、均匀的镍金属簇。此类金属簇非常重要，能够让一定量的材料最大限度地暴露活性表面。但是，金属簇也容易聚集在一起，导致反应能力受限。

To improve the performance and stability of these earth-abundant metal-based catalysts, Urban and his colleagues modified a strategy that focuses on tiny, uniform clusters of nickel metal. Tiny clusters are important because they maximize the exposure of reactive surface in a given amount of material. But they also tend to clump together, which inhibits their reactivity.

研究人员设计并进行了一次实验，通过将1.5纳米大小的镍簇沉积在2D基底上，防止金属簇聚集在一起。该2D基底由硼和氮制成的，被设计成原子大小、有凹槽的网格状。镍簇会均匀且牢牢地固定在凹槽中。此种设计不仅可以防止金属簇聚集，而通过直接与镍金属簇互动，催化剂的热化学性能也能得到大大提升，从而提升其整体性能。

they designed and performed an experiment that combatted clumping by depositing 1.5-nanometer-diameter nickel clusters onto a 2D substrate made of boron and nitrogen engineered to host a grid of atomic-scale dimples. The nickel clusters became evenly dispersed and securely anchored in the dimples. Not only did this design prevent clumping, but its thermal and chemical properties greatly improved the catalyst’s overall performance by directly interacting with the nickel clusters.

研究人员利用详细的X射线和光谱测量结果，结合理论计算，揭示了表面下的很多情况以及此类情况在催化反应中的作用。伯克利实验室采用先进光子源的工具和计算建模法，在微小镍金属簇在该2D基底上形成与沉积时，识别出该2D基底的物理与化学特性的变化。该研究小组提出，在金属簇占据基底原有区域并跟附近的边缘互动时，该材料就形成了，从而能够保留金属簇的微小尺寸。此种微小且稳定的金属簇促进了氢从液体载体中的分离，使该催化剂具有优异的分离性、生产率以及稳定性。

Detailed X-ray and spectroscopy measurements, combined with theoretical calculations, revealed much about the underlying surfaces and their role in catalysis. Using tools at the Advanced Light Source, a DOE user facility at Berkeley Lab, and computational modeling methods, the researchers identified changes in the physical and chemical properties of the 2D sheets while tiny nickel clusters occupy pristine regions of the sheets and interact with nearby edges, thus preserving the tiny size of the clusters. The tiny, stable clusters facilitated the action in the processes through which hydrogen is separated from its liquid carrier, endowing the catalyst with excellent selectivity, productivity, and stable performance.

计算表明该催化剂的尺寸使其能够比其他性能最佳的催化剂更具活性。研究人员利用模型和计算法揭示了该微小金属簇独特的几何与电子结构。大量裸露的金属原子聚集在此类微小的团簇上，比较大尺寸的金属粒子更能吸引氢气载体。此类暴露在外的原子还能够减缓氢气从载体中剥离的步骤，同时防止可能堵塞团簇表面的污染物的形成。因此，该材料在制氢反应的关键步骤中可以保持不被污染。此类催化和抗污染的性能被特意引入该2D基底，最终导致该团簇能够保持较小尺寸。

Calculations showed that the catalyst’s size was the reason its activity was among the best relative to others that have recently been reported. David Prendergast, director of the Theory of Nanostructured Materials Facility at the Molecular Foundry, along with postdoctoral research assistant and co-lead author Ana Sanz-Matias, used models and computational methods to uncover the unique geometric and electronic structure of the tiny metal clusters. Bare metal atoms, abundant on these tiny clusters, more readily attracted the liquid carrier than did larger metal particles. These exposed atoms also eased the steps of the chemical reaction that strips hydrogen from the carrier, while preventing the formation of contaminants that may clog the surface of the cluster. Hence, the material remained free of pollution during key steps in the hydrogen production reaction. These catalytic and anti-contamination properties emerged from the imperfections that had been deliberately introduced to the 2D sheets and ultimately helped keep the cluster size small.

在此次研究中，研究人员成功打造较便宜、容易获取以及稳定的材料，可帮助从液体载体中剥离氢气，使氢气能够用作一种燃料。该项研究基于美国能源部的计划，该计划旨在研究能够满足能源效率与可再生能源（EERE）氢气与燃料电池办公室对储氢材料的要求，并优化未来要用于车辆的材料。

In their catalyst, the researchers achieved the goal of creating a relatively inexpensive, readily available, and stable material that helps to strip hydrogen from liquid carriers for use as a fuel. This work came out of a DOE effort to develop hydrogen storage materials to meet the targets of EERE’s Hydrogen and Fuel Cell Technologies Office and to optimize the materials for future use in vehicles.

未来，伯克利实验室团队将进一步完善策略，以改变2D基底，使其能够为微小的金属簇提供支持，从而研发出更高效的催化剂。该技术有助于优化从液体化学载体中提取氢气的工艺。

Future work by the Berkeley Lab team will further hone the strategy of modifying 2D substrates in ways that support tiny metal clusters, to develop even more efficient catalysts. The technique could help to optimize the process of extracting hydrogen from liquid chemical carriers.