Control of the Ni non-stoichiometry in Ni_1-xO nanoparticles : "Core-shell"-like model

Baptiste Polteau (1) , Franck Tessier (1) , François Cheviré (1) , Laurent Cario (2) , Stéphane Jobic (2)

1 ISCR - Institut des Sciences Chimiques de Rennes
2 IMN - Institut des Matériaux Jean Rouxel

To improve the performances of p-Dye Sensitized Solar Cell (p-DSSC), the synthesis of modified p-type nickel oxide semiconductor, commonly used as a photocathode in such devices, was initiated using a mixed valent nickel oxyhydroxide Ni₃O₂(OH)₄. The decomposition of this precursor in air at temperatures lower than 600°C leads to non-stoichiometric Ni_1-xO nanoparticles (from 2 to 60 nm) with tunable nickel vacancies concentration (up to 25% for 2-3nm particle sizes). According to our chemical characterizations (XRD, TEM, density, chemical analysis, BET measurement…), the nickel vacancies segregate at the surface of the Ni_1-xO nanoparticles to create a "core-shell"-like edifice (similarly to our previous work on Zn-deficient Zn_1-xO nanoparticles). This "core-shell" is constituted by a dense stoichiometric NiO coated (or terminated) by an oxygen (hydroxide or carbonate groups) surface layer free from nickel atom. The Ni-free surface layer influences drastically the density of the smaller nanoparticles by decreasing it. When the nanoparticles size increases, the density evolves until reaching the theoretical density of stoichiometric nickel oxide for the bigger particles (≥100 nm). Thus, with the control of the particles size, we can also control the Ni non-stoichiometry in Ni_1-xO following our "core-shell"-like model.

Domaines: Matériaux

Baptiste Polteau, Franck Tessier, François Cheviré, Laurent Cario, Stéphane Jobic. Control of the Ni non-stoichiometry in Ni_1-xO nanoparticles : "Core-shell"-like model. "Solid State Chemistry" Gordon Research Conference (GRC), Jul 2016, New London, NH, United States. . ⟨hal-01560944⟩