Today, we can no longer imagine life without metals such as platinum (Pt), palladium (Pd), rhodium (Rh), ruthenium (Ru), osmium (Os) and iridium (Ir), known as platinum-group metals PGMs. Their biggest consumers are automotive catalysts, chemical industry, electronics, glass industry, jewelry, etc. Rhodium is thus one of the precious metals known for corrosion stability, high market value, exceptional catalytic properties, uneven geological distribution and the fact that it is lacking. Thus rhodium was placed on the list of critical raw materials (CRMs) in many countries, such as Europe, the United States and Japan. The current problem is that PGMs are not always recycled sufficiently end environmentally friendly. Even in landfills, we can find precious metals, which are usually processed with the same hydrometallurgical processes as in the processing of ores. These are energy-demanding and dangerous for the environment and people. One of the known processes is dissolving in aqua-regia. The risks of using this process are in particular the impact of toxic chemicals, the release of hazardous gases (HCl fumes, Cl2, NOx, nitrosyl chloride, etc.), leaching residues, high costs of reagents and equipment, elevated temperature, high pressure and pollution of water, etc. [1] Similar to the platinum dissolution [1], current study presents a new process in the rhodium recycling process, based on dissolution in dilute acids at atmospheric pressure, room temperature, salt addition (NaCl) and reactive gases (ozone, hydrogen and carbon monoxide). By exchanging the oxidative and reducing gases, oxidation and reduction of the rhodium surface achieved, which leads to aggressive corrosion called transient dissolution. Current efforts show that we are on the right track because we managed to dissolve up to 40% of the rhodium. In the future, we want to increase this percentage, by optimizing the system and procedure for commercial use. References: [1] Hodnik, N. et al. Platinum recycling going green via induced surface potential alteration enabling fast and efficient dissolution. Nat. Commun. 7, 13164 (2016).
B.04 Guest lecture
COBISS.SI-ID: 6506010Nanoparticles catalytic performance is determined by the atomically precise architecture of structure, composition and morphology of their surface and near-surface area. In the catalysis community, this is commonly referred to as the structure-activity relationship. However, predicting, understanding and finally, designing wanted nanocrystal structure at the atomic-scale is far from straightforward. Much progress has been achieved concerning the synthesis procedure of the so-called as-synthesized nanoparticles. However, when particles get exposed to real conditions and a process of activation and degradation, forming the actual active centers of electrocatalysts, much is still to be learned, especially in the case of Pt-alloys. Advancements in the scanning transmission electron microscopy together with identical location approach have made it possible to track the electrochemical changes of the individual Pt-based nanocrystals. Such atomic-scale mechanisms are supported by Monte-Carlo simulations and very sensitive online dissolution measurements (ICP-MS). Our novel advanced multidisciplinary approach paves the way to the atomic-scale understanding of the dynamic structural and morphological evolution of nanostructures and thus deeper understanding of the structure-stability relationship. Pt is one of the most studied electrocatalysts. However, degradation mechanisms have not been explored sufficiently. For instance, Pt nanoparticles are known to dissolve and also to detach from the catalyst support due to carbon corrosion and for agglomerates. Insight into these mechanisms can provide us twofold information: (1) how to stabilize Pt nanoparticles (new ceramic-based supports) and (2) completely new Pt hydrometallurgical recycling protocols.
B.04 Guest lecture
COBISS.SI-ID: 6716698Pt-alloy nanoparticles are the material of choice for the use as a cathode electrocatalysts in low-temperature fuel cells. However, due to their instability, it is difficult to define their atomic structure. An example of PtCu3 electrocatalyst dealloying will be discussed. Pt-SnO2 Janus type nanoparticles are an efficient anode electrocatalyst in direct ethanol fuel cells. Stability study of this system and others will serve as examples of our methodology approach in revealing the degradation at the atomic scale.
B.04 Guest lecture
COBISS.SI-ID: 6476314In this interview, Nejc Hodnik presented his field of work covering synthesis, characterization of catalysts and recycling of precious metals. The initiative for this interview was the recently acquired ERC Starting Grant project.
F.35 Other
COBISS.SI-ID: 6732570In 1800, renowned London surgeon Anthony Carlisle and chemist William Nicholson learned of the latest invention from Italy from the president of the most elite scientific institution of the time, the British Royal Society. It was a device from which a continuous flow of "electric fluid" - the battery. Within a few weeks, the silver and zinc plates and the intermediate layers of acid-soaked cones also assembled this instrument themselves and performed a special experiment with it - using battery and platinum wires, they split the water into hydrogen and oxygen. Nearly 220 years later, the study of materials for the electrochemical conversion of water is more vigorous than ever - even at the National Institute of Chemistry, where a new Electrocatalysis Laboratory was established this year.
F.35 Other
COBISS.SI-ID: 6796826