This study investigated the synthesis of platinum nanoparticles (Pt NPs) in ethylene glycol using low cost and low toxicity chemicals as reducing (ascorbic acid) and stabilizing agents (polyvinylpyrrolidone and sodium citrate). By monitoring the changes in the local chemical environment of the Pt atoms in real time by in situ dispersive X-ray absorption spectroscopy, it is observed that the NP formation kinetics involved three different stages within 3 h 30 min of the reaction: a reduction-nucleation burst, followed by diffusion-limited Ostwald ripening growth and subsequent stabilization of the NPs. The resulting Pt NPs were analyzed by transmission electron microscopy and X-ray diffraction, revealing a monodisperse average size distribution of 2.7 ± 0.5 nm, characterized by highly crystalline and stable Pt clusters, showing no significant aging for at least nine months.

The use of metal/oxide nanoparticles (NPs) as cocatalysts in heterogeneous photocatalysis is an important strategy to improve the photocatalytic activity of semiconductors for hydrogen generation. This article reports the use of a modified sputtering deposition method to prepare ultrafine NiO NPs cocatalysts dispersed on anodic Ta2O5 nanotubes (NTs). In situ X-ray absorption near-edge spectroscopy (XANES) measurements revealed that after exposing the as-prepared Ni NPs to air atmosphere a mixture of 68% of Ni and 32% of NiO was formed. Pure phase NiO NPs was successfully obtained after a controlled thermal oxidation at 500 °C which was confirmed by in situ XANES and ex situ XPS analyses. The photocatalytic hydrogen production activity was evaluated using ethanol as a sacrificial agent. Ta2O5 NTs with 0.16 wt % of NiO showed superior photocatalytic activity (up to 7.7 ± 0.3 mmol h–1 g–1) as compared to pure Ta2O5 NTs (4.9 ± 0.3 mmol h–1 g–1) The observed higher photocatalytic activity suggests that NiO/Ta2O5 NTs is a promising material for photocatalytic hydrogen evolution.

In the present study, in situ X-ray absorption spectroscopy (XAS) was used to monitor the structural evolution of isolated Pt 0.3 Pd 0.7 nanoparticles (NPs) subjected to different gaseous atmospheres. Time-resolved XAS measurements were performed at the Pt L 3 edge in the dispersive mode, during which X-ray absorption near edge spectra were sequentially collected. The NPs were initially activated under a reducing atmosphere at 300 °C (H 2 + He) and subsequently exposed to a sulfidation process at the same temperature (H 2 + He + H 2 S at 300 °C). Then, the sulfided NPs were thermally treated under a reducing atmosphere, and the reversibility of the sulfidation process was successfully accomplished, for the first time in these unsupported and well-characterized nanoscale systems. The atomic local order in the vicinity of the Pt atoms was investigated by extended X-ray absorption fine structure spectroscopy throughout all of these thermal treatments, monitoring the chemical stability of the metal−sulfur bonds and allowing kinetic modeling, from which the activation energies for the sulfidation process were estimated.

The use of in situ time-resolved dispersive X-ray absorption spectroscopy (DXAS) to monitor the formation of Cu2(OH)3Cl particles in an aqueous solution is reported. The measurements were performed using a dedicated reaction cell, which enabled the evolution of the Cu K-edge X-ray absorption near-edge spectroscopy to be followed during mild chemical synthesis. The formed Cu2(OH)3Cl particles were also characterized by synchrotron-radiation-excited X-ray photoelectron spectroscopy, X-ray diffraction and scanning electron microscopy. The influence of polyvinylpyrrolidone (PVP) on the electronic and structural properties of the formed particles was investigated. The results indicate clearly the formation of Cu2(OH)3Cl, with or without the use of PVP, which presents very similar crystalline structures in the long-range order. However, depending on the reaction, dramatic differences were observed by in situ DXAS in the vicinities of the Cu atoms.

We report a polyol synthesis method that provides controlled growth of chemically stable Cu nanoparticles with mean diameter easily tuned to lie below 10 nm.