Tuning properties of BImetallic supported catalysts with ultra-low NOble MEtal contents from solid to liquid state – BiNoMe

The project is based on a structured approach comprising three main stages aimed at designing more efficient catalysts while limiting the use of noble metals. The first stage consists of synthesizing very small nanoparticles (smaller than 10 nanometers) of copper, tin, and gallium. This step is the most challenging, as these metals are highly sensitive to oxidation and simple methods to produce them in a stable metallic form are still scarce. An additional challenge is the preparation of concentrated suspensions in order to obtain sufficient amounts of catalyst while precisely controlling particle size and chemical state.

The second stage focuses on depositing these nanoparticles onto a solid support widely used in catalysis, namely alumina. The challenge is to reach the desired metal loading while preserving the essential properties of the nanoparticles, in particular their small size and metallic state. The resulting materials are monometallic catalysts, which will serve as a foundation for the rest of the project and will also be evaluated for their intrinsic performance.

The third stage, at the core of the project, consists in introducing extremely small amounts of platinum onto these catalysts. The objective is to understand how the nature of the associated metal and the platinum loading influence catalytic efficiency. All materials are characterized and tested in the propylene production reaction in order to establish correlations between structure and performance, and to pave the way for more durable catalysts that make more efficient use of precious metals.

The project aimed to develop new, more efficient and more durable catalysts for propane dehydrogenation. The main challenge was to reduce the use of platinum, a rare and costly metal, by combining it with more abundant elements such as copper, tin, or gallium.

A first major achievement of the project concerns the fabrication of extremely small metallic nanoparticles, on the order of a few billionths of a meter. After the failure of conventional methods, a new mild chemical approach was developed, using a vitamin C derivative as a reducing agent. This method enabled the reliable synthesis of small copper, tin, and gallium nanoparticles at low temperature. Remarkably, some of these nanoparticles exhibit unusual crystalline structures that are rarely observed under normal conditions, opening new perspectives in materials science.

However, the project also revealed significant limitations. When attempting to deposit these nanoparticles onto a solid support—an essential requirement for industrial applications—they strongly interact with their environment. In particular, when brought into contact with alumina in water, a material widely used in catalysis to disperse nanoparticles, the particles rapidly oxidize, losing their metallic character and redistributing over the support surface. This oxidation is irreversible for gallium, whereas tin and copper can be reduced back to the metallic state, albeit with undesirable effects such as particle agglomeration in the case of tin. This difficulty highlights a major scientific bottleneck: it is extremely challenging to preserve non-noble metals in the metallic state when they are very small under the chosen conditions (use of water, exposure to air, alumina support).

Platinum was deposited in close proximity to the non-noble metals, but the formation of alloys was not demonstrated. Nevertheless, catalytic tests revealed a promising result. Among all the materials investigated, the system combining a very low platinum loading with gallium stood out due to its excellent stability and high propylene productivity, outperforming the conventional platinum-only catalyst. This suggests that gallium plays a beneficial role, even in the absence of direct alloy formation with platinum.

In conclusion, this project demonstrates that stabilizing non-noble metals is a central challenge in the design of more sustainable and resource-efficient catalysts. It opens up future directions, notably through the exploration of slightly larger particles or alternative supports, with the aim of developing industrial processes that are more respectful of resources and the environment.

The results of this project open several important perspectives for research and, in the longer term, for industry. First, they show that stabilizing non-noble metals in the metallic state is a central challenge. Future work may explore the use of slightly larger nanoparticles, which are less sensitive to oxidation, or alternative supports that are less reactive than alumina, in order to better preserve the properties of the metals.

Another key perspective concerns the design of more durable catalysts. The positive role of gallium, even in its oxidized form, suggests that subtle interactions between platinum, gallium, and the support can significantly improve catalyst stability. Understanding and exploiting these interactions could enable the development of catalysts that use less platinum while maintaining good performance, representing a major economic and environmental advantage.

Finally, beyond propane dehydrogenation, the concepts and methods developed in this work can be extended to other key industrial reactions and to other abundant metals. In the long term, this research contributes to the transition toward a more resource-efficient chemistry by reducing dependence on critical metals and improving the sustainability of chemical processes.

The BiNoMe project aims at developing new supported heterogeneous bimetallic catalysts with ultralow noble metal contents taking into account the possibility of forming bimetallic nanoparticles in the liquid or solid state during the reaction of propane dehydrogenation at high temperature, by playing on the melting temperature of the other metal component.
Bimetallic catalysts, prepared by surface redox reaction, will be characterized in depth at different stages of their life, not only after synthesis, but also during and after the catalytic reaction and the regeneration step. The combination of near operando transmission electron microscopy and theoretical modelling, taking into account the high temperature and the presence of reactive gases, will allow determining the interplay between surface structuration, state of the nanoparticles, catalytic properties and stability of the materials in the reaction conditions, opening the way to new formulations of highly performant catalysts.
This transdisciplinary project involves complementary academic research groups specialized in Chemistry (Heterogeneous catalysis), Physics (High resolution in situ TEM imaging and spectroscopy) and Theoretical modelling (DFT and multiscale simulation).