Origin of the Improved Photoelectrochemical and Photocatalytic Activity in a ZnO-TiO2 Nanohybrid Revealed by Experimental and Density Functional Theory Studies.

Heterojunctions of metal oxides have attracted a great deal of attention as photo (electro) catalysts owing to their excellent photoactivity. While multiple fundamental studies have been dedicated to heteroaggregation, self-assembly of oppositely charged particles to obtain heterojunctions for energy applications has been underexplored. Herein, we report the synthesis of ZnO-TiO2 heterojunctions using the electrostatic self-assembly approach. The synthesized ZnO-TiO2 heterojunctions were characterized by using multiple experimental techniques. Density functional theory calculations were conducted to establish the heterojunction formation mechanism and electronic properties. The ZnO-TiO2 nanohybrid was tested for the photodegradation of rhodamine B dye and water splitting applications. The photocatalytic performance of the ZnO-TiO2 nanohybrid is 3.5 times higher than that of bare ZnO. In addition, the heterostructure exhibited an excellent photocurrent density of 2.4 mA cm-2 at a low onset potential during photoelectrochemical oxygen evolution. The performance improvements are attributed to the formation of the type II heterojunction between ZnO and TiO2, which suppresses carrier recombination and enhances carrier transport, boosting the catalytic activity.

La(FeCuMnMgTi)O3 High-Entropy Oxide Nanoparticles as Highly Efficient Catalysts for Solvent-Free Aerobic Oxidation of Benzyl Alcohol.

In this work, a solid-state method for the synthesis of perovskite La(FeCuMnMgTi)O3 high-entropy oxide (HEO) nanoparticles is detailed. Additionally, the high performance of these nanoparticles as catalysts in the aerobic and solvent-free oxidation of benzyl alcohol is demonstrated. The structural features of HEO nanoparticles are studied by X-ray diffraction and high-resolution transmission electron microscopy. The La(FeCuMnMgTi)O3 nanoparticles demonstrate excellent benzyl alcohol conversion rates and selectivity for benzaldehyde, reaching 10.6% conversion and 52.8% selectivity after reaction for only 4 h and ≤75.6% conversion after 24 h. In addition, the as-prepared HEO catalyst displays robust stability in benzyl alcohol oxidation. Density functional theory calculations demonstrate that the adsorption energy of benzaldehyde on the HEO surface is lower than that of the benzoic acid. This, in turn, hinders the gradual conversion of benzaldehyde to benzoic acid on the surface of HEO and retains benzaldehyde as the main product.

Ferroelectric Polarization and Single-Atom Catalyst Synergistically Promoting CO2 Photoreduction of CuBiP2Se6.

Further improving the activity and selectivity of photocatalytic CO2 reduction remains a challenge. Herein, we propose a new strategy for synergistically promoting photocatalytic CO2 reduction by combining two-dimensional (2D) ferroelectric polarization and single-atom catalysis. Our calculations showed that the ferroelectric polarization of CuBiP2Se6 provides the internal driving force for the separation and migration of photogenerated carriers, which provides a prerequisite for enhancing the photocatalytic efficiency. In addition, the introduction of single Ag atoms can act as an electron reservoir to significantly modify the bonding configurations on the surface through proper static electron transfer, thus effectively promoting the adsorption and activation of CO2 molecules. More importantly, we found that switching the ferroelectric polarization can synergistically optimize the limiting potential as well as control the final products. This study provides a new approach for enhancing the catalytic activity and selectivity of photocatalytic CO2 reduction.

Density of states in the presence of spin-dependent scattering in SF bilayers: a numerical and analytical approach.

We present a quantitative study of the density of states (DOS) in SF bilayers (where S is a bulk superconductor and F is a ferromagnetic metal) in the diffusive limit. We solve the quasiclassical Usadel equations in the structure considering the presence of magnetic and spin-orbit scattering. For practical reasons, we propose the analytical solution for the density of states in SF bilayers in the case of a thin ferromagnet and low transparency of the SF interface. This solution is confirmed by numerical calculations using a self-consistent two-step iterative method. The behavior of DOS dependencies on magnetic and spin-orbit scattering times is discussed.

Anomalous current-voltage characteristics of SFIFS Josephson junctions with weak ferromagnetic interlayers.

We present a quantitative study of the current-voltage characteristics (CVC) of SFIFS Josephson junctions (S = bulk superconductor, F = metallic ferromagnet, I = insulating barrier) with weak ferromagnetic interlayers in the diffusive limit. The problem is solved in the framework of the nonlinear Usadel equations. We consider the case of a strong tunnel barrier such that the left SF and the right FS bilayers are decoupled. We calculate the density of states (DOS) in SF bilayers using a self-consistent numerical method. Then we obtain the CVC of corresponding SFIFS junctions, and discuss their properties for different set of parameters including the thicknesses of ferromagnetic layers, the exchange field, and the magnetic scattering time. We observe an anomalous nonmonotonic CVC in case of weak ferromagnetic interlayers, which we attribute to DOS energy dependencies in the case of small exchange fields in the F layers.