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Developing cocatalyst-free photocatalysts is highly desired because it could avoid the very slow interfacial electron transfer that makes photocatalytic photon utilization a dilemma. However, even in the optimal case, photocatalysts without the use of cocatalysts deliver comparable performance only for conventional construction. We demonstrate here that electronic doping not only provides catalytically active sites in cocatalyst-free photocatalysts but also plays certain additional roles. These electronic states can efficiently channel the trapped electrons to the semiconductor surface without suffering from time-consuming detrapping and can facilitate the extraction of photogenerated holes. These features endow our demonstrated tungsten-doped CdS with evident superiority in photocatalytic performance over conventional counterparts loaded with platinum cocatalysts.

Because of the complex composition of the apparent activation energy, the rate-determining step in a photocatalytic reaction like hydrogen evolution is still being explored even after sluggish oxygen evolution is replaced with efficient hole extraction. This issue severely limits the implementation of certain strategies like the synergistic thermal effect. Here, by developing a combined monitor method based on open-circuit potential decay, we demonstrate that semiconductor-cocatalyst interfacial electron transfer occurring on a decisecond to second time scale dominates photocatalytic hydrogen evolution. This time scale is approximately 6-12 orders of magnitude larger than the widely reported values of picoseconds to microseconds and is comparable to that predicted by Durrant et al. To improve photocatalytic hydrogen evolution, we manage to create more intermediate sites by electronically doping the semiconductor surface. This measure promotes semiconductor-cocatalyst interfacial electron transfer by charge recombination and makes the synergistic thermal effect very evident.

Because of very high potential barrier for thermionic emission and trap-assisted charge recombination, photocatalytic reaction rate that determined by semiconductor-cocatalyst interfacial electron transfer severely deviates from linearity to the photocatalyst dosage or to the light intensity. This makes it challenging to maximize utilization of practical irradiation by referring the parameters evaluated from method used in conventional catalysis. We here develop a model and predict that photocatalytic reaction rate positively correlates to photocatalyst concentration under weak illumination while the correlation becomes negative under intense irradiation. The theoretical simulation that matches the experimental values can be used to guide maximizing photocatalytic photon utilization under various intensity of irradiation. The strong correlation can rationalize photocatalytic evaluation instead of obtaining a numerically high value by excessively lowering the denominators. To realize efficient utilization of real-time changing sunlight, we propose a reactor configuration that can optimize the amount of photocatalyst participating into the reaction.

The major objective of the emerging photo-thermo-catalysis is using waste heat to boost the photocatalytic reaction, especially that powered by sunlight. Because of the complex composition of light-intensity-dependent apparent activation energies, the issue that principally hinders the synergistic thermal effect to photocatalysis has hardly been accurately explored. In this work, by virtue of mutual match of theoretical simulation and experimental behaviors, we demonstrate that photocatalytic reaction rates exhibit a sensitively positive correlation with temperature under weak illumination, in which charge recombination predominates the rate-determining step of semiconductor-cocatalyst interfacial electron transfer. Under high-intensity irradiation, however, the aggravation of charge leakage inherently accompanied by thermionic emission severely weakens the synergistic thermal effect or even slows down the reaction by raising the temperature. Inspired by these, we manage to maximize the photocatalytic solar utilization by spherical incidence of sunlight with the assistance of low-grade heat.

The electrochemical redox of p–nitrophenol was carried out with bare glassy carbon electrode modified by carbon encapsulated FeCu4 alloy nanoparticles by cyclic voltammetry. The reductive peak potential was positively moved and the value of redox peak currents were increased compared to the based on bare GCE. The conditions of the scan rate and the stability were also discussed. Through the cyclic voltammograms, we can know that the catalytic activity of the FeCu4/C nanoparticles increased with increasing the scanning rate in the range from 50 to 100 mVs–1. The results indicated that the bare GCE modified with FeCu4/C demonstrated perfect catalytic activity and stability for the degradation of p–NP.

As a common organic pollutant in industrial and agricultural wastewater, p-Nitrophenol (p-NP) is difficult to be degraded naturally. Though, various methods have been developed for degradation of p-NP, the utilization of catalysts to electrochemically degrade p-NP became a novel effective way. In this article, two magnetic nanoparticles (carbon-encapsulated iron, Fe/C; carbon-encapsulated cobalt, Co/C) were prepared. Through a series of physical phase characterization, we found that the average dimension of the prepared magnetic nanoparticles arrived at 60 nm for Fe/C and 80 nm for Co/C, and within such small dimensions, the prepared nanoparticles might have some remarkable catalytic characters in electrochemical degradation of p-NP. Therefore, two novel types of Fe/C and Co/C modified glassy carbon electrodes were fabricated to investigate their catalytic activity for p-NP degradation. In our results, both of the two modified electrodes showed favorable stability and excellent electro-catalytic activity for p-NP degradation. In addition, two modified electrodes also exhibited favorable electro-catalytic reductive ability for p-NP. The electrochemical reactions on the surface of the two modified electrodes were all diffusion controlled processes. Therefore, Fe/C and Co/C were excellent bifunctional catalysts which could be considered as a practical way to be applied in industrial hydrogenation and oxidative degradation of organic compounds.

A simple and efficient method for preparing graphitic carbon encapsulated rare-earth metal (lanthanum and europium) nanoparticles was explored. The samples were obtained by carbonizing a mixture of soluble metallic salt and dextrose at 773 K, and subsequently annealing the mixture at 1273 K in a nitrogen atmosphere. The annealed samples were studied by X-ray diffraction, high-resolution transmission electron microscopy, laser particle-size analysis and Raman spectroscopy. The results indicated that the samples prepared in our method were rather different from those described in previous publications. In these publications, the lanthanum (La) was encapsulated in the form of carbide and the europium (Eu) was not wrapped in graphitic carbon when the electric arc discharge method was used, while in our method, the rare-earth metal (La and Eu) nanoparticles were coated by graphitic carbon layers. Using the strategy mentioned above, which exploits a simple route to synthesize carbon encapsulated rare-earth metal nanoparticles with high yield, as much as 12–20 g of product can be prepared at one time. This strategy would be a prospective way for the application of rare-earth metal–carbon nanocapsules. A possible mechanism for the formation of the core–shell structure of these nanoparticles is discussed briefly.

In recent years, research interests in copper nanoparticles have been increased significantly due to their excellent performance in tribology, catalysis and many other fields. Howe ver, their applications have been still limited because the bare nanoparticles are easily oxidized. Ther efore, the study of copper nanoparticles encapsul ated in carbonaceous shells is an important issue. In this study, the carbon encapsulated copper nanoparticles were prep ared using copper nitrate as the metal sources and using sucrose as the carbon sources, through reducing and annealing. The phase, morphology, particle size and structure of as-prepared samples were charact erized using X-ray diffraction, field emission transmission electron microscopy, scanning electron mi croscopy and Raman spectroscopy, respec tively. The results indicate that the samples exhibit well core/shell structure, with sphere form and uniform size (50 nm in average). The copper cores consists of polycrystalline par ticles with fcc structure, whose size varies from 20 nm to 60 nm. The shell is amorphous carbon and its thickness is about 10 nm. In addition, the formation mechanism of carbon encapsulated copper nanoparticles was discussed and presented in the paper. Keywords: copper nanoparticles, core/shell, amorphous carbon, mechanism