Pd/Ni bimetallic modification of SrTiO3for enhancement of photocatalytic water splitting.

This paper investigates the impact of Pd/Ni modification on the photocatalytic hydrogen production performance of SrTiO3(STO). STO catalysts were synthesized using a hydrothermal method, and Pd/Ni modification was applied on the surface of STO through chemical deposition. Experimental results demonstrate that the hydrogen evolution rate of Pd/Ni-modified STO (Pd/Ni-STO) reaches 2232.14µmol g-1h-1. X-ray absorption fine structure spectroscopy analysis reveals substitutional doping of Ni with Ti and coordination of Pd with surface O. X-ray photoelectron spectroscopy analysis indicates the introduction of oxygen vacancies due to Pd/Ni doping. Density functional theory calculations suggest that Ni doping activates neighboring Ti atoms, leading to the formation of bimetallic catalytic sites composed of oxygen vacancies and Ti atoms, greatly enhancing the photocatalytic hydrogen evolution performance. This study not only provides an effective catalyst for photocatalytic applications but also offers insights into the underlying mechanism, which may stimulate the development of metal-doped catalytic materials and have implications for a range of other applications.

Ni-anchored g-C3N4for improved hydrogen evolution in photocatalysis.

In this study, we present a facile wet chemical method for synthesizing Ni-modified polymeric carbon nitride (g-C3N4) nanosheets. X-ray absorption fine structure spectroscopy reveals the formation of a unique Ni-N structure, resulting from Ni atoms anchoring in cavities of g-C3N4. The Ni anchoring on the surface N sites modifies the electronic structure of g-C3N4, demonstrating remarkable effectiveness even at low anchoring amounts. The as-prepared Ni/g-C3N4catalysts show robust performance for photocatalytic hydrogen evolution under visible light irradiation, attributed to the unique Ni-N interactions. Specifically, the photocatalytic H2production rate of the Ni/CN-45 catalyst reached 8482.14µmol·g-1·h-1with an apparent quantum efficiency of 0.75% under light irradiation at 427 nm. This rate surpasses most of the previously reported g-C3N4based photocatalysts and is nearly 8 times higher than that of the pure g-C3N4catalyst (1116.07µmol·g-1·h-1).

Gas-Sensing Mechanism of Silica with Photonic Bandgap Shift.

Two physical models, the replacing model and the filling model, have been proposed to explain the mechanism of the effective-refractive-index change of photonic crystals (PCs). Theoretically, the photonic bandgap (PBG) would shift when PCs are exposed to different environments, which leads to a change of the effective refractive index of PCs. However, the mechanism of effective-refractive-index change is distinct when PCs are placed in different gases or vapors. Here, silica PCs were successfully fabricated by a self-assembly method. The PBG of silica PCs exhibit similar redshifts in volatile organic compounds (VOCs) and in small-molecule gases. We propose a replacing model to elaborate silica PCs exposed to VOCs and a filling model to explain silica PCs exposed to small-molecule gases. Additionally, the redshift of PBG was transformed into the volume fraction of adsorbed gas in order to achieve selective sensing of silica PCs. The approach could be exploited for applications in sensing.

Highly Selective Gas Sensor Based on Hydrophobic Silica Decorated with Trimethoxyoctadecylsilane.

Trimethoxyoctadecylsilane (OTMS) was successfully used to decorate mesoporous silica with a self-assembly method to enhance the relative gas selectivity. A quartz crystal microbalance was employed to measure the gas-sensing properties. The content of OTMS was the crucial factor that greatly affected the adsorption capacity (q) of silica, which could be converted to relative selectivity (S) to study the sensing mechanism. With increasing OTMS content, q was far higher for small-molecule gases compared to volatile organic compounds (VOCs), which could be explained by the polarity of the bonding objects, and S reached a maximum value of 45.71%. When exposed to VOCs, S was always greater than 0 among the three alcohols. The sensing mechanisms of undecorated silica and OTMS-decorated silica were quite different; the three-state mechanism was proposed to explain the sensing mechanism of OTMS-decorated silica. When exposed to small-molecule gases, the atoms that bonded with carbon atoms on OTMS greatly influenced q. With increasing OTMS content, the bonding energy of OTMS with CO2 was far less than that with other molecules, resulting in a relative selectivity as high as 38.69%. Furthermore, macroperformance and microproperties were combined in three-dimensional coordinates, which could be applied to predict the sensing performance of silica.