Room-Temperature Synthesis of Nickel Borides via Decomposition of NaBH4 Promoted by Nickel Bromide

We report the formation of nickel borides, at room temperature and pressure, from the decomposition of NaBH4 promoted by the addition of nickel bromide at different concentrations in a dispersing organic medium, tetrahydrofuran and pentane. The nickel borides, formed as amorphous powders, were analyzed, and the structure information served as input for modeling a periodic lattice structure with the same composition. Experimentally, the nickel boride phases were predominantly composed of a boron-rich phase with composition NiB3. Combining FT-IR, X-ray diffraction analyses, and theoretical structure determination, we suggest for it a monoclinic structure, with symmetry group P2(1)/c(1) lattice parameters a = 3.038 angstrom, b = 8.220 angstrom, c = 5.212 angstrom, alpha = beta = 90.00 degrees and gamma = 87.57 degrees. The enthalpies of formation of the nickel boride phases, as well as the lattice stability, were calculated using density functional theory and density functional perturbation theory methods.