Supersonic Cluster Beam Deposition of Nanoalloys and Bimetallic Nanostructures for Enhanced Oxygen Evolution Reaction

Making Hydrogen synthesized by electrochemistry the best alternative to fossil fuels requires to overcome the slow kinetic of the oxygen evolution reaction (OER) in the electrochemical cell. The state-of-the-art OER electrocatalysts, based on nanoalloyed materials, face two main challenges still hindering the large-scale development: 1) the optimization of the electrode morphology and 2) the achievement of the catalyst stability under industrial prolonged activity. This PhD dissertation tackles both issues by synthesizing, through Supersonic Cluster Beam Deposition, a novel NiFe nanoalloyed electrode of controllable morphology, applied as OER catalyst under prolonged operational conditions. An in-depth physical, chemical and electrochemical characterization is carried out through several microscopy and spectroscopy techniques. The electrochemical characterization is carried out as a function of the NiFe morphology and mass loading within the 10 ng/cm2 – 30 ug/cm2 range. The data reveal that an excellent OER catalytic activity can be achieved, while the optimization of the NiFe morphology is accomplished by minimizing the NiFe mass loading without affecting the electrochemical efficiency. Conversely a procedure to stabilize the catalytic response in prolonged OER operation is proposed and correlated to chemical and morphological transformation of the electrode. These findings represent a crucial step towards the synthesis of affordable OER electrocatalysts in large-scale industrial applications. In the physical and chemical characterization of the NiFe films, the optical spectroscopy plays a crucial role. To this aim a new home-made software for the quantitative analysis of the UV-VIS-NIR optical spectra is developed and also applied to other Au and Ag based plasmonic system. In this framework, an advanced fabrication technique (nanoimprinting lithography and dynamic templating combined with liquid/solid interface growth) is employed to synthesize arrays of Au crystalline structures with an enhanced optical and plasmonic response. The investigation of such synthesis method and the design of specific plasmonic structures, combined with a through optical characterization, represent an advancement in a wide range of applications including sensing and nanoelectronics.