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Interfacial Schottky barriers can impact the catalytic function of Pt on TiO2. Since the electronic structure is characteristic of each material, it may be advantageous to tailor the interfacial Schottky barrier by the addition of adsorbed layers. Here, we show that the Schottky barrier in Pt/TiO2can be mitigated by the insertion of self-assembled monolayers (SAM) of carboranethiols that possess an oriented dipole moment. A Pt substrate with the SAM on which TiO2nanoparticles are deposited is used to that effect. Kelvin Probe Force Microscopy shows thatm-9-carboranethiolate SAM with perpendicular dipole moments decreases the potential difference between TiO2and Pt by ∼0.3 eV due to the interfacial electric field of the SAM. Our findings open new opportunities for tailoring interfacial electronic structures not only in the metal-semiconductor junction, but also the semiconductor heterojunctions.

This study investigated the ammonia decomposition mechanism over Ru/CeO2. Isotopic tests using ND3 revealed that the rate-determining step involves adsorbed nitrogen atoms on Ru. Moreover, an inverse kinetic isotope effect where ND3 decomposition was faster than NH3 was clearly observed. The origin of the inverse effect was explained by the lower D coverage on the catalyst surface compared to H coverage for mitigating the inhibition of ND3 activation. [ABSTRACT FROM AUTHOR]

Microwave‐driven catalytic processes have attracted the attention of many researchers and industries as these processes are powerful strategies for use in industrial electrification. However, undetectable hot spots inside the catalyst bed can be misleading in terms of the deceptive effects of microwaves on acceleration of catalytic reactions because of the lack of physicochemical knowledge about these processes. In this paper, the hot spots temperatures were estimated based on catalytic ammonia (NH3) synthesis/decomposition equilibrium. The reaction temperature estimated from the chemical equilibrium was more than 100 °C higher than the catalyst bed surface temperature measured with an infrared thermometer under microwave irradiation. Assuming a formation of very steep local high temperature fields, rigorous kinetic analysis led to an estimate that the active site fraction which reaches the high temperature was only about 10 % of total sites. Compared with a resistivity heating furnace, the energy input was reduced by more than 85 % under microwave irradiation. The temperature estimated by the chemical equilibrium was almost corresponding to the temperature estimated by an oscillation of extended X‐ray absorption fine structure recorded under microwave irradiation. This paper presents a proposal for a method to estimate hot spots based on thermodynamic equilibrium, yielding a quantitative evaluation of energy consumption reduction caused by microwaves. [ABSTRACT FROM AUTHOR]

Diverse crystal phases of bismuth (Bi) oxides induced by the addition of different amounts of tantalum (Ta) were synthesized. Their optoelectronic and redox properties were quantitatively investigated using combined experimental and computational approaches. Synthesis conditions that transform α-Bi2O3 into β-Bi2O3 and δ-Bi2O3 in terms of the Ta quantity, as well as synthesis temperatures, are identified and demonstrated. The phase transition behavior and crystal structures were characterized by in situ high temperature X-ray diffraction (XRD), thermogravimetry–differential thermal analysis (TG/DTA), X-ray absorption near edge structures (XANES), and extended X-ray absorption fine structures (EXAFS). Density functional theory calculations employing the HSE exchange–correlation functional with spin–orbit coupling were used to quantitatively simulate the optoelectronic properties and band structures of β-Bi2O3 and δ-Bi2O3. Along with the absorption coefficient and density of states, effective masses and dielectric constants were elucidated. The characterization study confirmed the distortion of Ta–O bonds in the Ta-supplemented β-Bi2O3 and the substitutional positions of the Bi and Ta atoms in the δ-Bi2O3 and Bi3TaO7 compounds. The reducibility of these oxides was strongly influenced by the crystal phase confirmed by temperature-programmed reduction (TPR) analysis. These findings can be used as a bismuth oxides' benchmark for optoelectronic applications as well as thermal catalysis as the redox active center or the support. [ABSTRACT FROM AUTHOR]

There are multiple requirements for maximizing the efficiency of photoelectrochemical overall water splitting using a single n‐type semiconducting photoanode. Many visible‐light‐responsive photoanode materials have been developed but overall water splitting by such materials without external bias has hardly been demonstrated. Herein, the aim is to scale the impact of performance improvement by an n–n heterojunction photoanode comprising an n‐type thin modification surface layer over an n‐type photon absorber, using a finite element method. For the n‐type photon absorber, the semiconductor properties are initially set to those of a well‐studied visible–light‐absorbing Ta3N5, and key properties are varied. It is demonstrated that an appropriate donor density and thickness of the thin surface layer induce adequate energy band bending in the photon absorber, resulting in a dramatic reduction of the onset potential of the photoanode. Thus, even though the quality of the photoanode is poor (e.g., the donor density is high (≈1 × 1019 cm−3)), the optimized surface layer enables the n–n heterojunction photoanode to facilitate bias‐free solar water splitting. These exhaustive investigations could provide design guidelines for obtaining effective photoanodes using an n‐type surface modification layer, such as cocatalysts and hole collection layers. [ABSTRACT FROM AUTHOR]