Nanocrystalline complex oxides NixCo3-xO4: Cations distribution impact on electrical and gas sensor behaviour

Nanocrystalline Oxides NixCo3−xO4: Sub-ppm H2S Sensing and Humidity Effect

“…Further oxidation of surface sulfites to sulfates by reaction (4) serves as an additional source of electrons, which increases the sensor signal at long times. In our previous work [19], it was shown that the concentration of chemisorbed oxygen on the surface of Ni0.1Co2.9O4 is lower than on Co3O4. This leads to a slowdown in the rate of reaction (2) and, as a result, led to a decrease in sensor signal toward 1 ppm H2S with increase in Ni content.…”

“…[20]. The phase composition, microstructure parameters and the charge state of cations were studied by XRD, TEM, XPS, EPR, as well as BET measurements [19]. The main characteristics of the samples are presented in Table 1.…”

“…One of the main limitations of Co3O4 as a material for gas sensors is its high electrical resistance. The introduction of nickel into the spinel structure with the formation NixCo3−xO4 (x ≤ 1) leads to a sharp drop in resistance of the material, which is realized due to an increase in the mobility of charge carriers at x ≤ 0.25 [19]. At the same time, a decrease in the concentration of chemisorbed oxygen is observed, correlating with a decrease in the proportion of Co 3+ in octahedral positions.…”

Triple Conductive Wiring by Electron Doping, Chelation Coating and Electrochemical Conversion in Fluffy Nb2O5 Anodes for Fast‐Charging Li‐Ion Batteries

“…In Figure 2i, the well-defined peaks can be observed for Co-NbO with two g values of 2.012 and 2.052. [30,31] Co doping enables the formation of electron-hole pairs in T-Nb 2 O 5 . The formation of oxygen vacancies resulting from cobalt doping can be described in the following formula…”

“…In Figure 2i, the well‐defined peaks can be observed for Co–NbO with two g values of 2.012 and 2.052. [ 30,31 ] Co doping enables the formation of electron‐hole pairs in T–Nb 2 O 5 . The formation of oxygen vacancies resulting from cobalt doping can be described in the following formula $$\begin{equation}{\rm{Nb}}_2{{\rm{O}}}_5\xrightarrow{{{\rm{CoO\ }}\left( { + 2} \right)\ }}2{{\rm{O}}}_{\rm{o}} + 3{\rm{V}}_{\rm{O}}^{ \cdot \cdot } + 2{\rm{C}}{{\rm{o^{\prime\prime\prime}}}}_{{\rm{Nb}}}\end{equation}$$or $$\begin{equation}{\rm{Nb}}_2{{\rm{O}}}_5\xrightarrow{{{\rm{Co}}_2{{\rm{O}}}_3\ \left( { + 3} \right)\ }}3{{\rm{O}}}_{\rm{o}} + 2{\rm{V}}_{\rm{O}}^{ \cdot \cdot } + 2{\rm{C}}{{\rm{o^{\prime\prime}}}}_{{\rm{Nb}}}\end{equation}$$where O o represents the lattice oxygen, $${\rm{V}}_{\rm{O}}^{ \cdot \cdot }$$ represents the oxygen vacancy with two units of positive charge, Co′′′ Nb and Co′′ Nb denote the substitution of Co atoms in Nb lattice sites with three and two units of negative charge respectively.…”