Thermochemical characteristics of Lan+1NinO3n+1 oxides

In situ variable temperature X-ray diffraction studies on the transformations of nano-precursors to La–Ni–O phases

“…Again, possible differences in oxygen partial pressure in the VT-XRD experiment may lead to the coexistence of La 2 NiO 4 and La 3 Ni 2 O 7 , rather than pure La 3 Ni 2 O 7 , as obtained in the electric muffle furnace under a similar heating regime. Although completely phase pure La 3 Ni 2 O 7 was not obtained, it could be concluded that the formation of La 3 Ni 2 O 7 was probably from the reaction of La 2 NiO 4 and NiO (in most cases, NiO characteristic peaks were not clearly visible due to its relatively poor X-ray scattering compared to the lanthanum-containing phases), which is consistent with suggestions in the literature [13,[19][20][21][22][23]. The phase changes observed in VT-XRD can be represented in Scheme 2.…”

“…In summary, from the VT-XRD results, it can be deduced that the phase changes for the syntheses of LaNiO 3 and La 2 NiO 4 are via the reaction of an amorphous or ill defined intimate mixture of La 2 O 3 and NiO (from initial La(OH) 3 and Ni(OH) 2 nano-precursors), which is consistent with the literature [13,[19][20][21][22][23]. See Scheme 1.…”

“…For the successful preparation of these phases with high purity, it is useful to understand the mechanisms under which phase formation occurs, since it is well known that phase pure syntheses of higher members of the La n þ 1 Ni n O 3n þ 1 series, particularly for n¼2 and 3 compounds (corresponding to the formulae La 3 Ni 2 O 7 and La 4 Ni 3 O 10 , respectively), are laborious and difficult, normally requiring prolonged heating (several days) and energy intensive re-homogenization procedures [4,[13][14][15][16][17][18]. There are only limited reports on thermodynamic data for the La-Ni-O system [13,[19][20][21][22][23] and to the best of our knowledge, there are no real-time in situ thermodynamic analytical studies of these compounds.…”

Scale-Down and Sr-Doping Effects on La4Ni3O10-δ–YSZ Nanocomposite Cathodes for IT-SOFCs

“…It affords many z E-mail: jyshin@deu.ac.kr; gtkim@unist.ac.kr advantages such as reasonable TECs, high oxygen ionic and electronic conductivity, and high electro-catalytic activity toward oxygen reduction. 15,17,18 The RP nickelate structure is composed of alternating perovskite layers (LaNiO 3 ) n and rock-salt layers (LaO) along the crystallographic c direction. From the La n+1 Ni n O 3n+1 (n = 1, 2, and 3) series, higher-order RP phase La 4 Ni 3 O 10-δ , can be regarded as the most suitable cathode material with high electrical conductivity, high cell performance, and better redox properties.…”

Partial oxidation of methane over bimetallic nickel–lanthanide oxides

“…f G • = −16.87 kJ/mol for the reduction of NiO and +1591.03 kJ/mol for the reduction of Gd 2 O 3 ) [64,65]. In the case of Pr 2 NiO 4 , to the best of our knowledge, only the enthalpy of formation ( f H • ) is known from the literature [66]. Nevertheless, the entropic factor has, for the reduction of NiO and Ln 2 O 3 , a positive sign, and the main contribution for the Gibbs free energy of solids is due to the gases (H 2 and H 2 O) produced during the reduction [64].…”