Reactive molecular dynamics simulations of nickel-based heterometallic catalysts for hydrogen evolution in an alkaline KOH solution

ST Oyinbo and TC Jen, COMPUTATIONAL MATERIALS SCIENCE, 201, 110860 (2022).

DOI: 10.1016/j.commatsci.2021.110860

In recent years, significant attention has been paid to the possible use of hydrogen (H2) as a renewable energy source. The formation of H2, in particular, is appealing by Ni-based-catalyzed activity in an alkaline potassium hydroxide (KOH) solution at room temperatures. However, a broader understanding of the reactions at the catalyst surface needs to be sought at the atomic level. In this research, a comparative and systematic study of nickel-based heterometallic catalysts in an alkaline potassium hydroxide (KOH) solution for H2 generation with the aid of ReaxFF potential is performed using reactive molecular dynamics (RMD) simulations. The interface composition of nickel catalyst was systematically modulated to include transition metals such as iron, platinum, and their oxides. All nickel-based transition metals and their oxides are equally active while influencing the catalytic reaction. Ni- Fe and Ni-Pt impose major promoting effects on the Ni-based catalyst, with an improvement in the generation rate of output of H2 when compared to the Ni-Fe-Pt heterometallic catalyst. On the other hand, only a marginal improvement in the catalytic effectiveness of the Ni-based catalyst is evident with Ni-Fe-O and Ni-Pt-O catalyst. The molecular proportion of the metal/(Ni + oxide) was varied within the catalyst to investigate the impact of metal combination and concentration on the alloy catalytic performance. This structural variation also explained the role of each second metal and their oxide involved in an alkaline KOH electron exchange process. The second metal promoting effects are mainly summarized in terms of the ability to serve as an electrophilic site for enhanced OH- group absorption, a large area of active surface, amorphous characteristic of the alloy catalyst, and interaction of the electrons with the Ni active metal.

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