Graphitic carbon nitride (g-C 3 N 4 ) has, since 2009, attracted great attention for its activity as a visible light-active photocatalyst for hydrogen evolution. Since it was synthesized in 1834, g-C 3 N 4 has been extensively studied both catalytically and structurally. While its 2D structure seems to have been solved, its 3D crystal structure has not yet been confirmed. This study attempts to solve the 3D structure of graphitic carbon nitride by mean of x-ray diffraction and of neutron scattering. Initially, various structural models are considered and their XRD patterns compared to the measured one. After selecting possible candidates as g-C 3 N 4 structure, neutron scattering is employed to identify the best model that describes the 3D structure of graphitic carbon nitride. Parallel chains of tri-s-triazine units organized in layers with an A-B stacking motif are found to describe the structure of the synthesized graphitic carbon nitride well. A misalignment of the layers is favorable because of the decreased π-π repulsive inter-layer interactions.

NiS2 is a cathode material found in primary batteries which operate at high temperature. Herein we report the in situ battery discharge study of a thermal battery cell which uses NiS2 as a cathode, using simultaneous collection of powder neutron diffraction data and electrochemical data. Five different regions were observed upon battery discharge and the evolution of nickel sulfide phases has been studied. Four different nickel‐containing phases are observed during discharge (NiS2, NiS, Ni3S2 and Ni). A new discharge mechanism has been proposed which does not include Ni7S6. Multiphase quantitative Rietveld refinement has allowed the percentages of the phases to be monitored during discharge. High intensity synchrotron powder X‐ray diffraction has been used to study the resulting phases present in the cathode after battery discharge.

Thermal batteries are an established primary battery technology and the most commonly used cathodes in these batteries are transition metal disulfides MS 2 (where M = Co, Ni and Fe). However, understanding the evolution of crystalline phases upon battery discharge has been hindered due to the high temperature operation of these batteries. Here we report an experiment that simultaneously collects powder neutron diffraction and electrochemical data as the battery is discharged. Four regions are observed in the diffraction data and four different cobalt containing phases are observed. Multi-phase Rietveld refinement has been used to monitor the evolution of phases during discharge and this is linked to the battery discharge profile. A new discharge mechanism has been proposed which involves hexagonal CoS instead of Co 3 S 4 , and the increase in unit cell parameters on discharge suggests the formation of a sulfur deficient solid solution before transformation to Co 9 S 8. This behavior seems reminiscent of that of NiS 2 suggesting that the discharge mechanisms of transition metal disulfides may have more similarities than originally thought.

Available online xxxKeywords: Ceria Impedance spectroscopy Electrical conductivity Oxide anode Solid oxide fuel cell a b s t r a c t Various metal oxide materials have been actively investigated to improve energy efficiency as exhaust-catalyst as well as electrodes in electrochemical devices such as fuel cells, ceramic sensors, photo-catalyst etc. Ceria-based materials are of great interest due to their wide applications; such as redox or oxygen storage promoter in automotive catalyst and solid state conductor in fuel cells. Here we report redox and electrical properties for Ce 1Àx M x O 2Àd (M ¼ Ni, Cu, Co, Mn, Ti, Zr) by X-ray diffraction (XRD) and simultaneous thermo-gravimetric analysis (TGA). Among various system, Ce 1Àx Cu x O 2Àd and Ce 1Àx Ni x O 2Àd indicated relatively reversible redox behavior, although Cu 2þ and Ni 2þ had limited solid solubility in CeO 2 . The enhancement of oxygen carrier concentration and electrical conductivity as well as electrochemical activity in the ceria lattice by the introduction of small amounts transition metal cations have been considered in this study. Ce 0.7 Cu 0.3 O 2Àdshowed about 1015 mmol[O 2 ]/g of oxygen storage capacity (OSC) with high redox stability at 700 C. We also demonstrated that Ce 0.9 Ni 0.1 O 2Àd was used as an anode of the YSZ electrolyte supported SOFC single cell; the maximum power density was 0.15 W/cm 2 at 850 C with hydrogen fuel.

Ionic conductivity is a phenomenon of great interest, not least because of its application in advanced electrochemical devices such as batteries and fuel cells. While lithium, sodium, and oxide fast ion conductors have been the subjects of much study, the advent of hydride (H − ) ion fast conductors opens up new windows in the understanding of fast ion conduction due to the fundamental simplicity of the H − ion consisting of just two electrons and one proton. Here we probe the nature of fast ion conduction in the hydride ion conductor, barium hydride (BaH 2 ). Unusually for a fast ion conductor, this material has a structure based upon a close-packed hexagonal lattice, with important analogues such as BaF 2 and Li 2 S. We elucidate how the structure of the high temperature phase of BaH 2 results in a disordered hydride sublattice. Furthermore, using novel combined quasi-elastic neutron scattering (QENS) and electrochemical impedance spectroscopy (EIS) we show how the high energy ions interact to create a concerted migration that results in macroscopic superionic conductivity via an interstitialcy mechanism.