Emergence and Stability of Copper Palladium Nitride Nanoparticles Studied by In Situ XAS and X-Ray Total Scattering

Transition metal nitrides are an interesting class of materials that attracted great attention recently due to their unique properties. They are potentially useful as electrocatalysts, photoactive materials for solar cells, optical data storage, and optoelectronic devices. Transition metal nitrides are less explored compared to the transition metal oxides. Because the synthesis of transition metal nitrides (TMNs) is highly challenging and often requires high temperature and high-pressure reaction conditions. Furthermore, the TMT nanoparticles are highly sensitive to moisture and transform into oxides. To overcome such issues, a second metal is doped with TMN forming the stable ternary transition metal nitride (TTMN). The doping element and the type of doping such as interstitial or substitutional doping could tune the electronic properties such as varying the bandgap from semiconductors to semi-metallic or metallic-like material.<br/>Here we report a one-pot, low-temperature synthesis of Cu₃PdN nanocrystals using primary amine as a solvent. The in-situ HERFD-XANES on the Cu K-edge reveals the type and structure of the initial metal complex and conversion of metal complex to nitrides. In situ total x-ray scattering measurements, PDF analysis and Rietfeld refinement enables to elucidate the nucleation and growth of the nitride nanocrystals. It also helps to understand the type of doping of the Pd atom in the Cu₃N crystal lattice and the sucessive transformation form Cu3PdN to Cu3Pd.<br/>The synthesized anti-perovskite type structured Cu₃PdN is further characterized with EXAFS, HR-TEM, UV-vis spectroscopy and TGA. Interestingly, the electrochemical measurements show that Cu₃PdN is a good catalyst for the hydrogen evolution reaction (HER). A detailed electrochemical study is being carried out.