The influence of silver (Ag) nanoparticles on the properties of poly(vinyl alcohol) (PVA) was investigated. The nanocomposite was prepared by mixing a colloidal solution consisting of silver nanoparticles with a water solution of PVA in appropriate ratios. Composite films with different contents of inorganic phase were obtained after solvent evaporation. The contents of the inorganic phase in the nanocomposites were determined by using atomic absorption spectroscopy (AA) for silver, and were found to be 0.19, 0.33, and 0.73 wt %. Transmission electron microscopy (TEM) of the nanocomposite films revealed the presence of Ag particles with average diameter of 20 nm. Comparison of the thermal properties of the pure polymer and the nanocomposite films showed that the thermal stability is improved by about 40 °C, and the glass transition temperature is shifted to a higher temperature up to 20 °C for the highest content of the nanofiller. An increase in Young's modulus and strength of the nanocomposite was also observed with an increase in Ag content, indicating significant reinforcement of the matrix in the presence of nanoparticles. Stress relaxation measurements revealed reduced stability of the nanocomposite upon prolonged loading, compared to the pure PVA matrix.

Photocatalytic approaches in the visible region show promising potential in photocatalytic water splitting and water treatment to boost water purification efficiency. For this reason, developing cost‐effective and efficient photocatalysts for environmental remediation is a growing need, and semiconductor photocatalysts have now received more interest owing to their excellent activity and stability. Recently, several metal oxides, sulfides, and nitrides‐based semiconductors for water splitting and photodegradation of pollutants have been developed. However, the existing challenges, such as high over potential, wide band gap as well as fast recombination of charge carriers of most of the semiconductors limit their photocatalytic properties. This review summarizes the recent state‐of‐the‐art first‐principles research progress in the design of effective visible‐light‐response semiconductor photocatalysts through several modification processes with a focus on density functional theory (DFT) calculations. Recent developments to the exchange‐correlation effect, such as hybrid functionals, DFT + U as well as methods beyond DFT are also emphasized. Recent discoveries on the origin, fundamentals, and the underlying mechanisms of the interfacial electron transfer, band gap reduction, enhanced optical absorption, and electron–holes separation are presented. Highlights on the challenges and proposed strategies in developing advanced semiconductor photocatalysts for the application in water splitting and degradation of pollutants are proposed.

Platinum is a noble metal that is widely used for the electrocatalytic production of hydrogen, but the surface reactivity of platinum toward water is not yet fully understood, even though the effect of water adsorption on the surface free energy of Pt is important in the interpretation of the morphology and catalytic properties of this metal. In this study, we have carried out density functional theory calculations with long-range dispersion corrections [DFT-D3-(BJ)] to investigate the interaction of H 2 O with the Pt (001), (011), and (111) surfaces. During the adsorption of a single H 2 O molecule on various Pt surfaces, it was found that the lowest adsorption energy (E ads ) was obtained for the dissociative adsorption of H 2 O on the (001) surface, followed by the (011) and (111) surfaces. When the surface coverage was increased up to a monolayer, we noted an increase in E ads /H 2 O with increasing coverage for the (001) surface, while for the (011) and ( 111) surfaces, E ads /H 2 O decreased. Considering experimental conditions, we observed that the highest coverage was obtained on the (011) surface, followed by the ( 111) and (001) surfaces. However, with an increase in temperature, the surface coverage decreased on all the surfaces. Total desorption occurred at temperatures higher than 400 K for the (011) and (111) surfaces, but above 850 K for the (001) surface. From the morphology analysis of the Pt nanoparticle, we noted that, when the temperature increased, only the electrocatalytically active (111) surface remained.

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