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[Display omitted] • Ni/Ce x Zr 1− x O 2 catalysts for ethanol steam reforming are prepared and tested. • Oxygen vacancy over Ce x Zr 1−x O 2 depends on lattice structures and Ni–CZ interaction. • The surface oxygen vacancy generates the active oxygen species for SR and WGS. • The abundant bulk oxygen vacancy enhances the H 2 production rate at 750 °C. • The lack of oxygen vacancies limits the oxygen vacancy–involving reaction routes. Ni/Ce x Zr 1−x O 2 catalysts were synthesized with two types of Ce x Zr 1−x O 2 solid solutions to understand the role of oxygen vacancy in ethanol steam reforming (ESR). The cubic Ce 0.93 Zr 0.07 O 2 (CZ) contained more oxygen vacancies on the surface and in the lattice structure than the tetragonal Ce 0.07 Zr 0.93 O 2 (ZC). Even though the Ni-Ce x Zr 1−x O 2 interaction basically increased the surface oxygen vacancy (OV S) on the interfacial region, it also induced different bulk oxygen vacancy (OV b) behavior: no OV b over Ni/ZC and no change over Ni/CZ. In the ESR, active oxygen species (O x) generated on the OV S simultaneously involved SR, and water gas shift reaction (WGS) to produce H 2. Zero OV b over Ni/ZC influenced the O x involving–reaction routes, resulting in the limitation of WGS and the high TOF values at 750 °C. Furthermore, since the OV b played a significant role as the O x carrier, Ni/CZ showed the highest H 2 production rate in the ESR at 750 °C. [ABSTRACT FROM AUTHOR]

Identically-sized AlGaN/GaN HFETs were fabricated on three AlGaN/GaN heterostructure with differing AlGaN barrier layer thicknesses of 15.5 nm, 19.3 nm and 24.7 nm. Based on polarization Coulomb field (PCF) scattering theory, additional polarization charges and electron mobility under the gate were calculated, and the relationship between AlGaN barrier layer thickness and P C F scattering in AlGaN/GaN H F E T s was determined. For the AlGaN/GaN H F E T s with a thicker AlGaN barrier layer, when the same gate bias was applied to the gate, the inverse piezoelectric effect (IPE) of the barrier layer was weaker, resulting in fewer additional polarization charges. The AlGaN/GaN H F E T s with a thicker AlGaN barrier layer also possessed a higher 2DEG sheet charge density, diminishing the P C F scattering intensity. It can be concluded that increasing the AlGaN barrier layer thickness reduces the IPE and raises the 2DEG sheet charge density, both of which decreases the PCF scattering intensity. The results of this study have guiding value toward the optimization of AlGaN/GaN HFETs materials and structures. • The relationship between AlGaN barrier layer thickness and polarization Coulomb field (PCF) scattering was determined. • Both of the reduce of additional polarization charges and the increase of the 2DEG density will weaken the PCF scattering. • PCF scattering intensity can be diminished by increasing the AlGaN barrier layer thickness. • The results of this study have guiding value toward the optimization of AlGaN/GaN HFETs materials and structures. [ABSTRACT FROM AUTHOR]