Center for Functional Nanomaterials Seminar

Due to their high specific surface area, nanoporous films hold great promise for a range of applications, including electrocatalysis, separation or sensing. To attain the desired chemistry and pore structure of the nanoporous films, it is essential to understand the process of film formation and the resulting film morphology. In situ monitoring of the evolution of the pore structure provides insights into the oftentimes complex mechanisms that take place during the nucleation and growth of the nanoporous films. Here, we introduce an in situ/operando approach to study the nanostructure of electrodeposited nanoporous films by Grazing Incidence Small Angle X-ray Scattering. Based on our custom-developed in situ electrochemical cell, we studied the film formation mediated by external electrochemical potentials, of mesoporous films that are relevant for fuel cell related applications, sensors or nanofluidic devices. Combining structural information from operando GISAXS with GIWAXS and the electrochemical data led to a deeper comprehension of the underlying mechanisms during film formation, i.e., the interplay between the electrodeposition dynamics and the resulting pore morphology. We explored two electrodeposition techniques to synthesize nanoporous metal films: First, using Lyotropic Liquid Crystal (LLC) templating for mesoporous Pt films, operando GISAXS revealed simultaneous nucleation of Pt and a decrease of the preferential orientation of the LLC close to the electrode, indicating a mutual interaction between the electrodeposition process and the LLC template, which led to vertical pore ordering in the electrodeposited Pt film[1]. Secondly, in the micelle-assisted electrodeposition of mesoporous PtNi films, comparing the evolution of parameters from electrochemistry, GISAXS and GIWAXS, we showed changes of the PtNi growth dynamics, from mesoporous structures with high long-range orders during nucleation of the PtNi film, to higher inter-pore distance and lower pore ordering. Our findings advance the understanding of electrochemical synthesis, contributing to the development of materials with tailored nanostructures.