Three-dimensionally hierarchical oxide/hydroxide materials have recently attracted increasing interest by virtue of their exciting potential in electrochemical energy conversion and storage. Herein, hierarchical Ni2(CO3)(OH)2 microspheres assembled from ultrathin nanosheets were successfully synthesized by a one-pot/one-step hydrothermal route. In this method, common nickel salts and urea were selected as raw materials. The influence of urea concentration on the final product was studied. The hierarchical Ni2(CO3)(OH)2 microspheres show weak crystallinity and contain crystalline water. It was found that they exhibit excellent rate capacity when used as supercapacitor electrode. Under current density of 0.5 and 10 A/g, the optimized Ni2(CO3)(OH)2 electrode with loading density of 5.3 mg/cm(2) exhibited specific capacitances of 1178 and 613 F/g with excellent cycling stability. The excellent electrochemical property is possibly attributed to the intrinsic nature of Ni2(CO3)(OH)2, the ultrathin thickness of nanosheet units, and the sufficient space available to interact with the electrolyte. This facile synthesis strategy and the good electrochemical properties indicate that hydroxycarbonates are promising materials for supercapacitor application. This study suggests a large library of materials for potential application in energy storage systems.

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Developing hybrid nanocrystals is a hot topic in materials science. Herein, a ternary hybrid nanocrystal, Ag-Ag2S-CdS, combining near infrared emission and photothermal conversion properties was demonstrated. The ternary Ag-Ag2S-CdS hybrid nanocrystals with cubic shape and uniform size were synthesized by a simple one-pot and one-step colloidal method. The growth process is self-regulated with the formation order of Ag2S, Ag, and CdS, sequentially. The formation of Ag originates from the partial reduction of Ag2S, while the formation of CdS is through an Ag2S catalytic mechanism based on its superionic feature. The obtained ternary hybrid nanocrystals show near infrared emission and photothermal conversion properties in a lab-on-a-particle system. Importantly, an enhanced effect is observed for the photothermal conversion, which is mainly due to the presence of heterointerfaces among the crystals. This work will not only advance the synthesis chemistry of multi-component hybrid nanocrystals but also provide a possible route for the design of advanced multi-model materials used in bio-related fields.

Photoelectrochemical (PEC) water splitting is a promising route for solar energy harvesting and storage, but it has been highly limited by the performance of the semiconductor photoelectrodes. Herein, we report a small molecular amine-mediated solvothermal method for synthesizing CdS nanorods. The obtained CdS nanorods are hydrophilic and can be easily dispersed in water. Furthermore, the small molecular amine, activating elemental sulfur and mediating the growth of CdS, all play a role similar to that of long-chain surfactant molecules in "non-aqueous" systems. Thus, the obtained CdS nanorods show uniform shape with monodispersed size, the length of which can be tuned by the sulfur dosage. In addition, the CdS nanorods show a broader light absorption than CdS nanoparticles. Their photoelectrochemical water splitting performances were then tested. Under light irradiation of λ > 200 nm, the photocurrent density of CdS nanorods at -0.2 V bias potential (vs. Ag/AgCl) is found to be 25 times of that obtained with CdS nanoparticles. The present finding demonstrates that small amine molecules could be efficient mediators for the synthesis of hydrophilic sulfides with high quality. The simple synthesis method and the good photoelectrochemical properties illustrate the hydrophilic CdS nanorods are potential candidate for photoelectrochemical applications.