Significance of This Article
The main target of our study, namely the catalytic activity of platinum and platinum-alloy nanoclusters, represents a forefront research field having a wealth of nanotechnological applications in next-generation catalysts design and synthesis. Platinum is widely used as a versatile three-way catalyst and is one of the best promising materials for practical usage for the conversion of toxic CO into harmless CO2. The subnanometer sized platinum clusters have large surface area and their effectiveness for the catalytic reaction of CO oxidation has been extensively studied by experimental researchers. However, to date, the detailed reaction mechanism still remains unclear. Moreover, the fact that tiny amounts of nano-scale size perform so efficiently represents a good point to reduce the cost of devices requiring the use of such an expensive noble metal. Nowadays, import, export and handling of natural resources such as rare metals is one of the major national concerns worldwide. Yet, the cost of the rare metal can still be a stumbling block in the realization of catalytic devices on an industrial scale. In this respect, replacing a pure platinum nanocluster with cheaper and common metals in whole or in part without reducing its catalytic activity is a key technological aspect for the synthesis and realization of commercially appealing and efficient catalysts. In the present work, we provide an answer to all these issues. More precisely, we clarify the full reaction mechanisms for the catalytic reactions of Pt8 and AlPt7 alloy clusters via enhanced first-principles dynamical simulations. Our approach is comprehensive of all the degrees of freedom of atoms and electrons and accounts explicitly for temperature effects. Entropic contributions to free-energy barriers for catalytic reactions and the fluxional and soft dynamical character of the clusters are fully considered, at variance with conventional static calculations generally used to tackle these problems. We provide a detailed route and propose viable solutions for reducing the amount of Pt atoms by replacing part of them with the cheaper aluminum without spoiling the catalytic activity. The proposed route provides a useful and convenient scheme to experimentalists and engineers working in the design of new effective Pt-based alloy catalysts. The key ideas that we propose can be summarized in (i) the tuning and control of the morphology, active sites, and electronic structure of the clusters by choosing proper supports and dopants and (ii) exploiting the intrinsic chemical character of each single component of the composed catalytic system. This general strategy paves the way to the new stage in catalyst design aimed at the production of efficient Pt-based catalysts keeping an eye to production costs and amounts of precious metals. Moreover, reducing the amount of rare metals is also noteworthy in terms of sustainability and environmental impact. For the reasons briefly summarized here and better detailed in the manuscript, we are convinced that the present contribution can have a strong impact and its broad interest is justified by the fact that our findings are addressed to a wide spectrum of academic and industrial researchers active in a diversified range of fields from chemistry to material science.