The crucial bottleneck in water electrolysis is the employment of expensive and scarce iridium in unsustainable amount. Namely, Ir is even ten times more scarce then platinum and is also declared by EU and other countries as CRM (critical raw material). To solve this two tactics can be taken. The first one is to increase Ir intrinsic OER performance, so we get more current per mass of Ir on the electrode. The second one is to effectively disperse Ir into fine nanoparticles onto high-surface-area support (e.g. high-surface area carbon). However, under extremely corrosive conditions found in typical PEM electrolyzer, carbon is not stable. In the very recent collaborative study with IJS, we explored (project leader as corresponding author) the feasibility of using both tactics in one innovative nanocomposite material based on a titanium oxynitride (TiONx). We dispersed Ir on high-surface-area support in the form of nanoparticles, however, at the same time, we also tuned its intrinsic activity and stability via support interaction. With this we obtained record-high Ir performance according to available literature data. Importanly, we utilized state-of-the-art characterization techniques to analyze our samples and prove our theory that indeed support effects should be considered more strongly not just to disperse active centers (like Ir nanoparticles) but also to increase its activity and stability. With this we delivered new directions to the electrocatalysis community where future developments of OER electrocatalysts should also go in the direction of tuning supports and not solely in optimizing active particles/centers itself. The described study is a case example of synergistic collaboration with project team members and IJS.
COBISS.SI-ID: 45043203
Our very recent collaborative study with IJS (partner organization in the present action) is an impactful contribution to the field of electrocatalysis. Project team members (project leader as corresponding author) justified this by introducing an efficient approach for the production of electrocatalytic films via anodization-based synthesis. The selected candidate consisted of iridium nanoparticles immobilized on a titanium oxynitride substrate (TiONx). By executing an identical location characterization we thoroughly described the electrode preparation process whereas density functional theory (DFT) calculations reveal the origins of beneficial electrochemical performance. Convincing evidence show that confinement inside the pores and strong metal-support interaction (SMSI) effects reduce the tendency for sintering of Ir nanoparticles which leads to unprecedented electrochemical durability substantially exceeding the performance of the industry benchmark material. By this, we are solving the great challenge of lowering Ir loading in the electrolysers and at the same time provide stable and conductive support.
COBISS.SI-ID: 36706819
Nanoparticulate electrocatalysts are one of the pillars of sustainable energy conversion. One of the main bottlenecks in more rapid technological development is the synthesis of electrocatysts where catalytic performance is typically achieved onyl in the case of miligram amounts of catalysts. In order for technological breakthrough same catalytic performance should be translated to larger batches. However this is rarely realized in practice as synthesis of large amounts of nanoparticulate catalyst does not deliver sufficent electrocatalytic performance. In this very recent study project team members invented a robust and realiable synthesis which enables to deliver sufficient amount of nanoparticles powder to be directly tested in membrane electrode assemblies (MEAs), unit component of a fuel cell. The synthesis approach used here exploits simple principles of electrodeposition. More specific platinum precursor is spontaneously electrodeposited on copper/carbon based support obtained by sol-gel method. As the driving force and crucial ingredient for electrodeposition is the so-called double passivation. This is based on using carbon monoxide as capping agent preventing the growth of Pt nanoparticles and ambiental air to passivate Cu nanoparticles via formation of surface oxides. As a result small and homogeneous Pt-Cu nanoparticles are formed after annelaing treatment. The process of their formation was monitored and described with cutting edge characterization, i.e., in-situ annealing TEM diagnostics. The key advantages of such an approach over other synthesis methods are that i) it can be performed in a water-based system (involves no complex organic solvents), ii) it is performed at room temperature and ambient pressure (making it highlly Green) and importantly, iii) the synthesis is easily scalable to gram scale or more without sacrificing any catalytic performance of Pt-Cu. With the introduction of such synthesis we solved a long lasting paradigm of how to prepare large enough batches of platinum based electrocatalysts without losing electrocatalytic performance, which is of significant importance for fuel cell community. The skills obtained and lessons learned in this study namely, electrodeposition, in-situ heating TEM characterization and exploitation the principles of Green Chemistry will be instrumental to synthesize electrocatalytic nanoparticles in the proposed research project, where similarly structured catalayst are foreseen.
COBISS.SI-ID: 6648858
Electrochemical gas evolution reactions are of vital importance in numerous electrochemical processes including water splitting, chloralkaline process, and fuel cells. During gas evolution reactions, gas bubbles are vigorously and constantly forming and influencing these processes. In the past few decades, extensive studies have been performed to understand the evolution of gas bubbles, elucidate the mechanisms of how gas bubbles impact gas evolution reactions, and exploit new bubble-based strategies to improve the efficiency of gas evolution reactions. In this article, we introduce for the first time an electrochemical apparatus to effectively remove electrochemically generated bubbles. Such methodology could easily be employed to all gas evolving or gas consumin electrochemical reactions.
COBISS.SI-ID: 32578343
Catalytic properties of advanced functional materials are determined by their surface and near-surface atomic structure, composition, morphology, defects, compressive and tensile stresses, etc; also known as a structure–activity relationship. The catalysts structural properties are dynamically changing as they perform via complex phenomenon dependent on the reaction conditions. In turn, not just the structural features but even more importantly, catalytic characteristics of nanoparticles get altered. Definitive conclusions about these phenomena are not possible with imaging of random nanoparticles with unknown atomic structure history. Using a contemporary PtCu-alloy electrocatalyst as a model system, a unique approach allowing unprecedented insight into the morphological dynamics on the atomic-scale caused by the process of dealloying is presented. Observing the detailed structure and morphology of the same nanoparticle at different stages of electrochemical treatment reveals new insights into atomic-scale processes such as size, faceting, strain and porosity development. Furthermore, based on precise atomically resolved microscopy data, Kinetic Monte Carlo (KMC) simulations provide further feedback into the physical parameters governing electrochemically induced structural dynamics. This work introduces a unique approach toward observation and understanding of nanoparticles dynamic changes on the atomic level and paves the way for an understanding of the structure–stability relationship.
COBISS.SI-ID: 6623002