High entropy alloys (HEAs) and compositionally complex alloys (CCAs) have recently attracted great research interest because of their remarkable mechanical and physical properties. Although many useful HEAs or CCAs were reported, the rules of phase design, if there are any, which could guide alloy screening are still an open issue. In this work, we made a critical appraisal of the existing design rules commonly used by the academic community with different machine learning (ML) algorithms. Based on the artificial neural network algorithm, we were able to derive and extract a sensitivity matrix from the ML modeling, which enabled the quantitative assessment of how to tune a design parameter for the formation of a certain phase, such as solid solution, intermetallic, or amorphous phase. Furthermore, we explored the use of an extended set of new design parameters, which had not been considered before, for phase design in HEAs or CCAs with the ML modeling. To verify our ML-guided design rule, we performed various experiments and designed a series of alloys out of the Fe-Cr-Ni-Zr-Cu system. The outcomes of our experiments agree reasonably well with our predictions, which suggests that the ML-based techniques could be a useful tool in the future design of HEAs or CCAs.

properties could be achieved for their use in a variety of important applications, such as wastewater remediation, [4][5][6][7][8] catalysis, [9,10] energy storage, [11] and fuel cells. [12] Recently, a similar design principle was proposed by metallurgists to enhance the chemical complexity of alloys through the synthesis of multi-principal element alloys, also known as high entropy alloys (HEAs), [13,14] for enhanced mechanical properties. [13,15,16] In addition, some HEAs also show promising functional properties, such as super-paramagneticity and superconductivity. [17,18] Interestingly, it is noteworthy that most HEAs reported so far contain active transition metals, [19] such as Ni, Co, and Fe, which are commonly used for electrochemical catalysis; however, to our best knowledge, the research on HEAs for electrocatalysis is still rare.In the broad field of clean energy, it is critical to promote oxidation reaction and O 2 production in the state-of-the-art energy storage devices, such as fuel cells and metal oxygen batteries. However, the kinetics of such reactions, which is of a multistep process, [19] is usually sluggish; therefore, high performance electrochemically catalytic materials are in great need today to improve the efficiency of oxygen evolution Designing active, stable, yet low cost electrocatalysts for the oxygen evolution reaction (OER) is pivotal to the next generation energy storage technology. However, conventional OER catalysts are of low electrochemical efficiency while the state-of-the-art nanoparticle-based catalysts require mechanical supports, thereby limiting their wide deployment. Here, it is demonstrated that, due to the excellent corrosion resistance of the Fe-Co-Ni-Cr-Nb high entropy intermetallic Laves phase, fabricating a high entropy bulk porous nanostructure is possible by dealloying the corresponding eutectic alloy precursor. As a result, a core-shell nanostructure with amorphous high entropy oxide ultrathin films wrapped around the nanosized intermetallic ligaments is obtained, which together, exhibits an extraordinarily large active surface area, fast dynamics, and superb long-term durability, outperforming the existing alloy-and ceramic-based OER electrocatalysts. The outcome of the research suggests that the paradigm of "high entropy" design can be used to develop high performance catalytic materials.

The rise of nanotechnology has been propelled by low dimensional metals. Albeit the long perceived importance, synthesis of freestanding metallic nanomembranes, or the so-called 2D metals, however has been restricted to simple metals with a very limited in-plane size (< 10 m). In this work, we developed a low-cost method to synthesize 2D metals through polymer surface buckling enabled exfoliation. The 2D metals so obtained could be as chemically complex as high entropy alloys while possessing in-plane dimensions at the scale of bulk metals (> 1 cm). With our approach, we successfully synthesized a variety of 2D metals, such as 2D high entropy alloy and 2D metallic glass, with controllable geometries and morphologies.Moreover, our approach can be readily extended to non-metals and composites, thereby opening a large window to the fabrication of a wide range of 2D materials of technologic importance which have never been reported before.

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