Iron oxides are promising to be utilized in rechargeable alkaline battery with high capacity upon complete redox reaction (Fe 3+ Fe 0 ). However, their practical application has been hampered by the poor structural stability during cycling, presenting a challenge that is particularly huge when binder-free electrode is employed. This paper proposes a "carbon shellprotection" solution and reports on a ferroferric oxide-carbon (Fe 3 O 4 -C) binder-free nanorod array anode exhibiting much improved cyclic stability (from only hundreds of times to >5000 times), excellent rate performance, and a high capacity of ≈7776.36 C cm −3 (≈0.4278 C cm

The development of photocatalysts with superior activity and stability to produce organic fuels through CO2 reduction under renewable sunlight is of great significance due to the depletion of fossil fuels and severe environmental problems. In this study, we presented a “hitting three birds with one stone” strategy to synthesize carbon layer coated cuprous oxide (Cu2O) mesoporous nanorods on Cu foils via a facile chemical oxidation and subsequent carbonization method. The thin carbon layer not only works as a protective layer to quench the common photocorrosion problem of Cu2O but also endows the sample a mesoporous and one-dimensional nanorod structure, which can facilitate reactant molecule adsorption and charge carrier transfer. Substantially, the coated samples exhibited remarkably improved stability as well as decent activity for CO2 reduction under visible light irradiation. The optimized sample attained an apparent quantum efficiency of 2.07% for CH4 and C2H4 at λ0 400 nm, and 93% activity remained after six photoreduction cycles under visible light. This work provides a facile strategy to address the stability and activity issues of Cu2O under visible light irradiation, which is presumably suitable for other semiconductors as promising candidates for CO2 reduction in artificial photosynthesis.

No abstract

Iron oxide is promising for use in aqueous energy storage devices due to the high capacity, but one of the most challenging problems is cycling instability within the large potential window that results from the complete quasi-conversion reaction. Herein, a conformal surface coating strategy toward iron oxide via atomic layer deposition (ALD) is presented and an Fe 3 O 4 @TiO 2 core-shell nanorod array anode is reported that exhibits remarkable cycling performance exceeding 30 000 times within a wide potential window in neutral lithium salt electrolyte. ALD offers a uniform and precisely controllable TiO 2 shell that not only buffers the inner volume expansion of Fe 3 O 4 , but also contributes extra capacity through Li + intercalation/de-intercalation and helps to alleviate the water electrolysis. Furthermore, by pairing with a pseduocapacitive cathode of V 2 O 3 @carbon and using a hydrogel electrolyte of PVA-LiCl, a unique flexible quasi-solid-state hybrid supercapacitor can be assembled. With a high voltage of 2.0 V, the device delivers high volumetric energy and power densities (2.23 mWh cm −3 , 1090 mW cm −3 ), surpassing many recently reported flexible supercapacitors. This work highlights the importance of ALD conformal multifunctional shell to instable nanoarray electrodes in aqueous electrolytes and brings new opportunities to design advanced aqueous hybrid energy storage devices.

How to take advantage of CO 2 has been one of the main issues to be addressed around the world. Although there are many methods to convert CO 2 to organic fuel, the efficiency is still not high enough for practical application. Herein, we have accomplished better conversion of CO 2 by the combination of metal electrode and semiconductor thin films responsive to visible light. First, the deposition of p-type and n-type Cu 2 O thin films onto a Cu substrate is successfully achieved. Then, the prepared Cu/Cu 2 O samples are used for catalytic reduction of CO 2 in photoelectrochemical systems in comparison with that in photochemical and electrochemical systems. The results show that CH 4 and C 2 H 4 are the major hydrocarbon gas products, and the prepared Cu/Cu 2 O samples have much higher selectivity for C 2 H 4 formation compared with the pure Cu electrode. The best yield for CO 2 reduction is obtained in the photoelectrochemical system under visible light. Additionally, CO 2 conversion efficiency over the Cu/Cu 2 O (p-type) electrode is much higher than that over Cu/Cu 2 O (n-type) with similar morphology. The morphology of Cu 2 O has an effect on the CO 2 reduction activity in the photoelectrochemical system as well. The related mechanism is discussed in detail especially for the reaction in the beginning 15 min. The study will provide us a new way to utilize solar light for efficient conversion of CO 2 into organic fuel.