In situ XAS visualization of the formation of the active sites in Ni-Nx-C catalysts for the hydrogen reduction reaction

Nickel coordinated within pyridinic nitrogen on a carbon backbone structure (Ni-N-C) has extraordinary electrocatalytic activity towards hydrogen evolution reaction (HER). Ni-N-Cs can substitute platinum group metal (PGM) in order to reduce device costs. Synthesys for these electrocatalysts is based on pyrolytic processes with controlled temperature and atmosphere. The identification of the metal containing active sites and understanding of their formation during pyrolysis is crucial to enhance the M-N-C synthesis processes and active site reactivity. X-ray Adsorption Spectroscopy (XAS) will be used to reach our main goal, to define speciation of the Ni during pyrolysis, occurring at constant T (up to 800°C with 50°C step). This in-situ study, supported by ex-situ samples prepared at constant temperature, will: i) reveal the dynamics formation of Ni containing active sites during pyrolysis; ii) identify the temperature in which the desired active sites are formed.