In Situ Diffraction Study of Catalytic Hydrogenation of VO₂: Stable Phases and Origins of Metallicity

Abstract

Controlling electronic population through chemical doping is one way to tip the balance between competing phases in materials with strong electronic correlations. Vanadium dioxide exhibits a first-order phase transition at around 338 K between a high-temperature, tetragonal, metallic state (T) and a low-temperature, monoclinic, insulating state (M1), driven by electron-electron and electron-lattice interactions. Intercalation of VO2 with atomic hydrogen has been demonstrated, with evidence that this doping suppresses the transition. However, the detailed effects of intercalated H on the crystal and electronic structure of the resulting hydride have not been previously reported. Here we present synchrotron and neutron diffraction studies of this material system, mapping out the structural phase diagram as a function of temperature and hydrogen content. In addition to the original T and M1 phases, we find two orthorhombic phases, O1 and O2, which are stabilized at higher hydrogen content. We present density functional calculations that confirm the metallicity of these states and discuss the physical basis by which hydrogen stabilizes conducting phases, in the context of the metal-insulator transition.

X-ray Absorption Spectroscopy Study of the Effect of Rh doping in Sr2IrO4

“…It effectively increases the electronegativity of O p in Ir-O p bond, thereby making the Ir-O p bond ionic. Similar mechanism but opposite trend has been discussed in H doped VO 2 30. The enhanced ionic character of the Ir-O p bond can decrease hybridisation between two ions.…”

Sequential insulator-metal-insulator phase transitions of VO2 triggered by hydrogen doping

“…It is reported that hydrogen incorporated into M-VO 2 crystals can stabilize the metallic VO 2 phase at room temperature [10][11][12][13][14] and further lead to an insulating phase in the high doping regime [15]. Explained in the context of crystal-field theory [16,17], the H-doping induced band structure evolutions is represented in Fig.…”

Electrochemical gating-induced reversible and drastic resistance switching in VO2 nanowires

“…Of the prototypical materials, VO 2 is promising as it undergoes a metal-insulator transition (MIT) and the resistance changes by orders of magnitude around 340 K. In VO 2 nano to microstructures5678910111213, the coupling of the MIT with mechanical789, optical13, thermal12 and electronic properties911 can be used in tunable resonators, optical switchers, electronic and thermo-sensing devices. Furthermore, only a few atomic percent of the hydrogen- or oxygen-intercalation and -desorption in VO 2 cause drastic changes in the transport properties, equal to that caused by inducing the MIT14151617181920. Conventionally, controlling the amount of hydrogen/oxygen ions in an oxide has been conducted by annealing the samples under redox gas atmospheres141516, in an aqueous solution1718 and with a hydrogen spillover method1419.…”