The development of new types of renewable clean energy is the focus of attention in the current material field. Hydrogen, due to its extremely high mass energy density and non-polluting products, has become a potential alternative clean energy, and the use of high-performance catalysts to achieve low-energy water decomposition of hydrogen is currently one of the main means of obtaining hydrogen energy.
How to improve the performance of the catalyst, including its catalytic activity and its long-term stability, is one of the key issues affecting the application of hydrogen energy. To date, known high catalytic activity material systems, including commercially available Pt/C catalysts, have mostly crystalline structures, which are difficult to solve due to their characteristic high active sites and a single metastable local structure. Long-term stability issues.
Researcher Wang Weihua of the Institute of Physics of the Chinese Academy of Sciences and Sun Chunwen, a research fellow at the Beijing Institute of Nano Energy and Systems, Chinese Academy of Sciences, and the Guan Pengfei Group, a researcher of the Thousand Talents Program at Beijing Research Center for Computational Science, have discovered that Pd-based amorphous alloys ( Also known as Metallic Glass, MG) as a catalyst for the electrochemical decomposition of water, not only exhibits excellent catalytic activity, but also possesses unique self-stability.
Metallic glass is an alloy material formed by rapid cooling of high-temperature melts. Its unique microstructure, namely short-range, medium-range order, and long-range disordered atomic arrangement, makes metal glasses have unique properties that are different from those of crystalline alloys, such as high Due to its high strength, high elasticity, corrosion resistance, and soft magnetic properties, it has broad application prospects in some high-tech materials. Pd-based metallic glass has excellent and unique properties as a catalytic material and may be a potential functional catalytic material.
The research work was mainly completed by Ph.D. students Hu Yuanchao, Cao Yuxi, Master Wang Yizhi and Dr. Su Rui. They chose an alloy system with excellent glass forming abilityâ€”Pd40Ni10Cu30P20 amorphous strip as the catalytic material for electrochemical decomposition of water. Based on the research model combining experimental and theoretical simulation, the catalytic activity and stability of the material were explored, and the microscopic mechanism was revealed. The study found that the material has an initial catalytic activity comparable to a commercially available 10 wt% Pt/C catalyst, but has superior long-term stability.
The metal-glass catalyst has a low overvoltage even after 10,000 cycles of circulation (Fig. 1); more importantly, its catalytic activity has a distinctly different slow decay than the rapid decay of a commercial Pt/C catalyst. The trend, even after more than 40,000 seconds of use, is still about 100% efficient (Figure 1). Compared with about 100 catalytic materials that have been reported in the current literature (Fig. 2), the performance of the metallic glass is superior to that of most of the crystalline catalytic materials, and exhibits a unique self-stability. Based on X-ray photoelectron spectroscopy, electrochemical impedance spectroscopy and first-principles calculations, it was found that the rich local structure, chemical inhomogeneity and evolution of metallic glass surfaces are the origin of the micro-structure of its excellent properties. First-principles calculations further indicate that the surface of the metallic glass is rich in highly active sites related to the distribution of local chemical elements (Fig. 3, the free energy âˆ† GH is approaching 0), and the selectivity that occurs during the catalytic reaction The alloying makes the proportion of high active sites on the surface of the material increase at the initial stage of the reaction (reduction of Ni and P elements), and further shows the tendency of catalytic activity to rise; on the other hand, the intrinsic non-uniformity of the surface of the metallic glass contributes to a high level of enrichment. The type of active site has the advantage of slowing down the performance degradation compared to a single active site type of crystalline material. Related results were recently published in Advanced Materials (2016) on the topic of A Highly Efficient and Self-Stabilizing Metallic Glass Catalyst for Electrochemical Hydrogen Generation.
The research was funded by the National Natural Science Foundation of China, the "973" Project, the Youth 1000 Program, the Chinese Academy of Sciences and the Beijing Computational Science Research Center.
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