New Catalytic Materials from Amorphous Metal Alloys

Strain engineering of high-entropy alloy catalysts for electrocatalytic water splitting

Developing active and cost-effective bifunctional electrocatalysts for overall water splitting is challenging but mandatory for renewable energy technologies. We report a high-entropy alloy (HEA) of PtIrCuNiCr as a bifunctional electrocatalyst for overall water splitting, which shows a low overpotential of ca. 190 mV at the current density of 10 mA cm^-2. Compared with pure metals, HEAs exhibit remarkable surface strain due to severe lattice distortion in their crystal structures. Theoretical calculations reveal that the strain can regulate the binding energy of intermediates on catalysts by adjusting the metal-metal bonding energy. It pushes the HEA toward the top of volcano plots to achieve superior electrocatalytic activity for both hydrogen and oxygen evolution reactions. The strain effect of HEAs on electrocatalysis can be well engineered by tuning the catalyst radius or configurational entropy. This work renders a systematic strain regulation strategy for designing a high-performance HEA catalyst for overall water splitting.

Catalysis of Alloys: Classification, Principles, and Design for a Variety of Materials and Reactions

Alloying has long been used as a promising methodology to improve the catalytic performance of metallic materials. In recent years, the field of alloy catalysis has made remarkable progress with the emergence of a variety of novel alloy materials and their functions. Therefore, a comprehensive disciplinary framework for catalytic chemistry of alloys that provides a cross-sectional understanding of the broad research field is in high demand. In this review, we provide a comprehensive classification of various alloy materials based on metallurgy, thermodynamics, and inorganic chemistry and summarize the roles of alloying in catalysis and its principles with a brief introduction of the historical background of this research field. Furthermore, we explain how each type of alloy can be used as a catalyst material and how to design a functional catalyst for the target reaction by introducing representative case studies. This review includes two approaches, namely, from materials and reactions, to provide a better understanding of the catalytic chemistry of alloys. Our review offers a perspective on this research field and can be used encyclopedically according to the readers' individual interests.

Stabilizing Hydrous β-NiOOH for Efficient Electrocatalytic Water Oxidation by Integrating Y and Co into Amorphous Ni-Based Nanoparticles

A two-stage ball milling process was used to synthesize amorphous Ni_79.2Nb_12.5Y_8.3 and Ni_74.2Co₅Nb_12.5Y_8.3 nanoparticles from elemental powders. The two-stage ball milling process provides a scalable and industrially applicable method for producing non-metalloid amorphous nanoparticles. The amorphous nanoparticles displayed excellent catalytic performance toward the oxygen evolution reaction (OER) in 1 M KOH, displaying lower overpotentials than IrO₂ at 10 mA cm^-2. The addition of Co in the amorphous alloy reduced the overpotential to 288 mV at 10 mA cm^-2. The pairing of X-ray photoelectron spectroscopy and in situ X-ray absorption spectroscopy revealed that the improved OER activity of amorphous Ni_74.2Co₅Nb_12.5Y_8.3 was attributed to the catalytic synergy between Y and Co. The integration of Y supported proton-coupled electron-transfer processes that assisted with the electrostatic adsorption of OH^- and formation of oxyhydroxide species, while Co sites enabled metal-oxo bonding to prevent Ni overcharging and the stabilization of β-NiOOH. The catalytic synergy between Y and Co reduces the amount of Co needed to enhance the OER activity of Ni-based alloys and lessens the dependence on Co, which is in high demand in many renewable energy and storage applications.

Preparation of Nicob/SiO2 Nanoalloy Catalysts and their Catalytic Hydrogenation Performance

The nanoalloy NiCoB and NiCoB/SiO2 catalysts were prepared by an incipient impregnation-chemical reduction method with NaBH4. They were characterized and examined for their catalysis in the hydrogenation of furfural to furfural alcohol. NiCoB and NiCoB/SiO2catalysts were characterized by XRD as amorphous structure. The amorphous NiCoB/SiO2catalyst was active in the hydrogenation of furfural, and it was significantly more active than NiB, CoB and NiCoB.