Abstract:

X-ray spectroscopy plays a pivotal role in unraveling the electronic structure of 3d transition metal oxides (TMOs), providing insights into valence states, spin states, covalence, and charge transfer. Advanced techniques such as X-ray absorption spectroscopy (XAS), resonant inelastic X-ray scattering (RIXS), photoemission spectroscopy (PES), and resonant photoemission spectroscopy (RPES) are essential for exploring the electronic properties of heterogeneous catalysts (under operando conditions) and superconductive nickelate thin films. 

Operando Hard X-ray spectroscopy offers bulk sensitivity, but probing the near-surface electronic properties requires ultra-thin epitaxial films. These films, typically grown on X-ray transparent membranes, exhibit high crystallinity and a single out-of-plane crystal orientation, enabling detailed operando measurements. 
In this talk, I will discuss: (1) the dynamics of spin and (co)valence in La(Mn, Fe, Co, and Ni)O3 perovskite oxides thin films (3-4 nm) under operando solid-liquid interfaces (electrocatalytic oxygen evolution reaction) and solid-gas interfaces using operando hard and soft X-ray absorption (XAS) as well as 1s2p resonant inelastic X-ray scattering (RIXS); (2) the ground state properties of recently discovered superconductive nickelate thin films by RPES guided by impurity (cluster model and LDA + DMFT AIM) calculations.