Among the various methods for the preparation of nanoparticles, a sparking process at atmospheric pressure is of interest because it is a simple method for producing nanoparticles ranging from a few nanometer-sized particles to agglomerated film structures. In this research, we studied the effects of metal electrode properties on nanoparticle sizes. The experiments were carried out by applying a high voltage to different metal sparkling tips. The transfer of energies from positive ions and electron bombardments induced the melting and vaporization of electrode metals. Based on this research, we have developed a model to describe the formation of a nanoparticle film on the substrate, placed under the sparking gap, and the nanostructure produced by metal vapor on the sparking electrodes. The model provides a realistic tool that can be used for the design of a large-scale coating and the application of nanoparticles developed by this process for the filtration of PM2.5 mask fabric by air.

Water electrolysis has received much attention in recent years as a means of sustainable H 2 production. However, many challenges remain in obtaining high-purity H 2 and making large-scale production costeffective. This study provides a strategy for integrating a two-cell water electrolysis system with solar energy storage. In our proposed system, CuO-Cu(OH) 2 /Cu 2 O was used as a redox mediator between oxygen and hydrogen evolution components. The system not only overcame the gasmixing issue but also showed high gas generation performance. The redox reaction (charge/discharge) of CuO-Cu(OH) 2 /Cu 2 O led to a significant increase (51%) in the initial rate of H 2 production from 111.7 μmol h −1 cm −2 in the dark to 168.9 μmol h −1 cm −2 under solar irradiation. The effects of light on the redox reaction of CuO-Cu(OH) 2 /Cu 2 O during water electrolysis were investigated by in situ X-ray absorption and photoemission spectroscopy. These results suggest that surface oxygen vacancies are created under irradiation and play an important role in increased capacitance and gas generation. These findings provide a new path to direct storage of abundant solar energy and low-cost sustainable hydrogen production.

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In this work, we study and compare the photo-induced conductivity of a two-dimensional electron gas (2DEG) at the bare surface of SrTiO3 (STO) and in the heterostructure of BiFeO3 (BFO) and STO, where BFO was deposited by radio frequency magnetron sputtering. The photo-induced conductance of the BFO/STO interface shows a large increase which is 20.62 times more than the sum of photo-induced conductance from each individual BFO thin film and STO crystal. Since this photo-induced conductance of the BFO/STO heterostructure can be adjusted to become higher and lower by applying an electric field to the top surface, we attribute this large increase to the strong photo-induced electrical polarization of BFO. With the two-point setup of positive bias and negative bias, the conductivity also exhibits diode-like behavior where the forward and backward resistances are different. This work provides methods to interplay between light irradiation, electric field, and conductivity in all-oxide electronics.