Spinel

Abstract: Through direct nanoparticle nucleation and growth on nitrogen doped, reduced graphene oxide sheets and cation substitution of spinel Co3O4 nanoparticles, a manganese–cobalt spinel MnCo2O4/graphene hybrid was developed as a highly efficient electrocatalyst for oxygen reduction reaction (ORR) in alkaline conditions Electrochemical and X-ray near-edge structure (XANES) investigations revealed that the nucleation and growth method for forming inorganic–nanocarbon hybrids results in covalent coupling between spinel oxide nanoparticles and N-doped reduced graphene oxide (N-rmGO) sheets Carbon K-edge and nitrogen K-edge XANES showed strongly perturbed C–O and C–N bonding in the N-rmGO sheet, suggesting the formation of C–O–metal and C–N–metal bonds between N-doped graphene oxide and spinel oxide nanoparticles Co L-edge and Mn L-edge XANES suggested substitution of Co3+ sites by Mn3+, which increased the activity of the catalytic sites in the hybrid materials, further boosting the ORR activity compared with th

Abstract: Through direct nanoparticle nucleation and growth on nitrogen doped, reduced graphene oxide sheets and cation substitution of spinel Co3O4 nanoparticles, a manganese-cobalt spinel MnCo2O4/graphene hybrid was developed as a highly efficient electrocatalyst for oxygen reduction reaction (ORR) in alkaline conditions. Electrochemical and X-ray near edge structure (XANES) investigations revealed that the nucleation and growth method for forming inorganic-nanocarbon hybrid results in covalent coupling between spinel oxide nanoparticles and N-doped reduced graphene oxide (N-rmGO) sheets. Carbon K-edge and nitrogen K-edge XANES showed strongly perturbed C-O and C-N bonding in the N-rmGO sheet, suggesting the formation of C-O-metal and C-N-metal bonds between N-doped graphene oxide and spinel oxide nanoparticles. Co L-edge and Mn L-edge XANES suggested substitu-tion of Co3+ sites by Mn3+, which increased the activity of the catalytic sites in the hybrid materials, further boosting the ORR activity compared to the pure cobalt oxide hybrid. The covalently bonded hybrid afforded much greater activity and durability than the physi-cal mixture of nanoparticles and carbon materials including N-rmGO. At the same mass loading, the MnCo2O4/N-graphene hybrid can outperform Pt/C in ORR current density at medium overpotentials with superior stability to Pt/C in alkaline solutions.

Abstract: In the Sc 2 O 3 Ga 2 O 3 CuO, Sc 2 O 3 Ga 2 O 3 ZnO, and Sc 2 O 3 Al 2 O 3 CuO systems, ScGaCuO 4 , ScGaZnO 4 , and ScAlCuO 4 with the YbFe 2 O 4 -type structure and Sc 2 Ga 2 CuO 7 with the Yb 2 Fe 3 O 7 -type structure were obtained. In the In 2 O 3  A 2 O 3  B O systems ( A : Fe, Ga, or Al; B : Mg, Mn, Fe, Ni, or Zn), InGaFeO 4 , InGaNiO 4 , and InFe 3+ MgO 4 with the spinel structure, InGaZnO 4 , InGaMgO 4 , and InAlCuO 4 with the YbFe 2 O 4 -type structure, and In 2 Ga 2 MnO 7 and In 2 Ga 2 ZnO 7 with the Yb 2 Fe 3 O 7 -type structure were obtained. InGaMnO 4 and InFe 2 O 4 had both the YbFe 2 O 4 -type and spinel-type structures. The revised classification for the crystal structures of AB 2 O 4 compounds is presented, based upon the coordination numbers of constituent A and B cations.