Liquid Platinum at Room Temperature: The “Cool” Catalyst for a Sustainable Revolution in Industrial Chemistry

Chemical reactions can be accelerated by the presence of catalysts, which is crucial for industrial chemistry. Platinum, however, makes a great catalyst for several reactions, although it is rather expensive. In actuality, it is a precious metal with a higher value than gold.

Because of this, developing new, less priced catalysts is tremendously beneficial. Researchers have combined liquid gallium and platinum in the same manner.

Australian researchers have developed low-cost, highly effective chemical reactions using trace amounts of liquid platinum, paving the possibility for significant emissions reductions in key industries.

The amounts of platinum needed, when combined with liquid gallium, are so small as to significantly increase the earth's platinum reserves, as well as possibly providing more sustainable solutions for CO2 reduction, ammonia synthesis in fertilizer production, and the development of green fuel cells, among many other potential uses in the chemical industries.

When it comes to the potential of these catalytic systems, our findings, which concentrate on platinum, are but a drop in the ocean of liquid metals. By developing on this strategy, there may be more than a thousand possible elemental combinations for a multitude of reactions.

An atomic representation of the catalytic system, with red spheres standing in for platinum atoms and silver spheres for gallium atoms. The catalytic processes are highlighted by the little green and blue spheres, which represent the reactants and products, respectively. Credit: UNSW Sydney's Dr. Md. Arifur Rahim

Due to its high cost, platinum is not frequently employed on an industrial scale even though it is an extremely powerful catalyst (the start of chemical reactions). The majority of platinum-based catalysis systems require significant amounts of continual energy to run.

Platinum typically melts at a temperature of 1,768 °C (3,215 °F). And in a carbon-based catalytic system, there needs to be about 10% platinum when it's employed in a solid state for industrial reasons.

When trying to produce parts and goods for commercial sale, it's an unaffordable ratio.

But after researchers from the University of New South Wales (UNSW) Sydney and RMIT University discovered a way to use minuscule amounts of platinum to trigger potent reactions without having to expend a lot of energy, that may change in the future.

The researchers coupled platinum with liquid gallium, which has a melting point of just 29.8°C, or what is considered room temperature on a hot day. The collaboration also included members of the ARC Centre of Excellence in Exciton Science and the ARC Centre of Excellence in Future Low Energy Technologies. The platinum dissolves when mixed with gallium. In other words, it melts without the need for a large industrial furnace to be turned on.

Processing at a high temperature is only necessary to establish the catalytic system in this mechanism's initial step, when platinum is dissolved in gallium. Even then, the temperature is nowhere near the continuous high temperatures sometimes required in industrial-scale chemical engineering; it is only around 300°C for around an hour or two.

Dr. Jianbo Tang, a contributor from UNSW, compared it to a blacksmith utilizing a hot forge to create long-lasting equipment.

When working with iron and steel, you must heat it in order to create a tool, but once you have it, you never have to heat it again.

Others have tried this method, but they are forced to constantly run their catalytic systems at extremely high temperatures.

The researchers discovered that a platinum to gallium ratio of less than 0.0001 was necessary to produce a catalyst that worked. The system that was created was, perhaps most astonishingly, almost 1,000 times more efficient than its solid-state competitor (which required platinum that was about 10% more expensive to function).                                                                                                               

The benefits don't end there, though, since the liquid-based technology also makes it more dependable. Over time, solid-state catalytic systems develop clogs and malfunction. Here, that is not a concern. The liquid mechanism constantly regenerates itself, much like a water feature with a built-in fountain, maintaining its efficacy over time and preventing the catalytic equivalent of pond scum accumulating on the surface.

"Since 2011, scientists have been able to miniaturize catalyst systems down to the atomic level of the active metals," stated Dr. Md. Arifur Rahim, the lead author from UNSW Sydney. The typical systems require the stabilization of solid matrices (like graphene or metal oxide) to keep the single atoms apart from one another. Why not try a liquid matrix instead and see what happens, I reasoned.

"Atoms anchored to a solid matrix that are used in catalysis are stationary. By employing a liquid gallium matrix, we have increased the mobility of the catalytic atoms at low temperatures.

The mechanism is adaptable enough to carry out both oxidation and reduction reactions, in which a substance receives oxygen or loses it, respectively.

To comprehend these astounding results, the UNSW experimenters had to solve some puzzles. Their RMIT colleagues, under the direction of Professor Salvy Russo, were able to determine that the platinum never solidifies, right down to the level of individual atoms, using cutting-edge computational chemistry and modeling.

Dr. Nastaran Meftahi, an Exciton Science Research Fellow, explained the importance of the modeling work done by her RMIT team.

The two platinum atoms never came into contact with one another, according to what was discovered, she said.

"Gallium atoms had always separated them. In this system, no solid platinum is formed. In the gallium, it is always atomically distributed. That's pretty remarkable, because it matches what we discovered through modeling, which is really challenging to directly observe through testing.

Surprisingly, gallium, acting under the influence of platinum atoms nearby, actually does the work of triggering the desired chemical reaction.

These results are novel, according to Exciton Science Associate Investigator Dr. Andrew Christofferson of RMIT. "The platinum is actually a little bit below the surface and it's activating the gallium atoms around it," he said. Gallium is therefore undergoing the magic under the effect of platinum.

"But it doesn't happen without the platinum there. From what I can tell, this is absolutely distinct from any previous catalysis that has been demonstrated. And modeling is the only way that this could have been demonstrated.

Low-temperature liquid platinum catalyst was described in "Low-temperature liquid platinum catalyst" by Md. Arifur Rahim, Jianbo Tang, Andrew J. Christofferson, Priyank V. Kumar, Nastaran Meftahi, Franco Centurion, Zhenbang Cao, Junma Tang, Mahroo Baharfar, Mohannad Mayyas, Francois-Marie Allioux, Pramod Koshy, Torben Da

By ARC CENTRE OF EXCELLENCE IN EXCITON SCIENCE