Li(2)ZrN(2): Crystal Structure, Electronic Properties, Oxidative Stability, Thermal Behavior, and Catalytic Activity in Ammonia Decomposition.

Catalytic ammonia (NH(3(g))) decomposition is a carbon-neutral chemical process for hydrogen generation. Transition metal nitrides are particularly promising in this regard due to their unique catalytic properties. This study takes a closer look at the crystal structure, explores the thermal behavior under NH(3), and evaluates the catalytic activity of Li(2)ZrN(2) for ammonia decomposition. Phase-pure Li(2)ZrN(2), synthesized via solid-state reaction at 900 °C, crystallizes in the La(2)O(3)#CaAl(2)Si(2)-type structure in space group P3Ì m1 (No. 164). Rietveld refinements and atomic parameters align well with previous studies. The unit cell parameters obtained are a = 3.2826(3) à and c = 5.4611(5) à . First-principles density-functional theory (DFT) calculations reveal an optical band gap of 2.50 eV, consistent with the experimentally determined value of 2.46 eV, and a low lattice thermal conductivity (1.52 W·m(-1)·K(-1)), suggesting its suitability for energy applications. X-ray photoelectron spectroscopy (XPS) and Raman spectroscopy confirm the ionic Li-N and covalent Zr-N bonding in Li(2)ZrN(2). In situ X-ray diffraction analysis and thermogravimetric analysis coupled with mass spectrometry (TG-MS) reveal complex decomposition pathways of Li(2)ZrN(2) under NH(3), impacting catalytic activity. Ammonia decomposition initiates above 500 °C and improves with successive heating-cooling cycles, likely due to the formation of active sites.