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TiO2 has been well studied as an ultraviolet (UV) photocatalyst and electrode material for lithium‐ion rechargeable batteries. Recent studies have shown that hydrogenated TiO2 displayed better photocatalytic and lithium ion battery performances. Here it is demonstrated that the photocatalytic and battery performances of TiO2 nanocrystals can be successfully improved with a facile low‐temperature vacuum process. These TiO2 nanocrystals extend their optical absorption far into the visible‐light region, display nanometer‐scale surface atomic rearrangement, possess superoxide ion characteristics at room temperature without light irradiation, show a 4‐fold improvement in photocatalytic activity, and has 30% better performance in capacity and charge/discharge rates for lithium ion battery. This facile method could provide an alternative and effective approach to improve the performance of TiO2 and other materials towards their practical applications.

High-power batteries require fast charge/discharge rates and high capacity besides safe operation. TiO2 has been investigated as a safer alternative candidate to the current graphite or incoming silicon anodes due to higher redox potentials in effectively preventing lithium deposition. However, its charge/discharge rates are reluctant to improve due to poor ion diffusion coefficients, and its capacity fades quickly with rate as only thinner surface layers can be effectively used in faster charge/discharge processes. Here, we demonstrate that surface-amorphized TiO2 nanocrystals greatly improve lithium-ion rechargeable battery performance: 20 times rate and 340% capacity improvement over crystalline TiO2 nanocrystals. This improvement is benefited from the built-in electric field within the nanocrystals that induces much lower lithium-ion diffusion resistance and facilitates its transport in both insertion and extraction processes. This concept thus offers an innovative and general approach toward designing battery materials with better performance.

Titanium dioxide (TiO 2 ) is important for both fundamental studies and technical applications. Here we present laser power dependence Raman spectroscopic studies of rutile TiO 2 to reveal the response of various Raman-active lattice vibrations. Apparently, different vibrational modes display distinctive and reversible trends with the change of laser power. The Ti−O bond strength involved with different vibrational modes changes differently as the laser power changes. The relaxation time becomes shorter as the laser power increases. The changes of the bond strength and relaxation time can be related to the local temperature change with the laser power. The observed different behaviors in the vibrational modes suggest that the lattice movements along various directions face different temperature environments under the same light irradiation.

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Special structure of materials often bring in unprecedented catalytic activity which are critical in realizing large-scale hydrogen production by electrochemical water splitting.Herein, we report CoO/MoO x crystalline/amorphous structure as an effective bifunctional electrocatalyst for water splitting. Converted from CoMoO 4 by hydrogenation, the CoO/MoO x , featured with crystalline CoO in amorphous MoO x matrix, displays superior catalytic activities toward both hydrogen evolution reaction (HER) and oxygen evolution reaction (OER). It shows small onset overpotentials of 40 and 230 mV for the HER and OER in 1.0 M KOH, respectively, and overall water splitting starting at 1.53 V with a robust stability. The high catalytic activity of the CoO/MoO x is benefited from the large defect-rich interface between CoO and MoO x , along with the amorphous nature of MoO x . Thus, this study demonstrates the effectiveness of structural manipulation in developing highly active electrocatalysts for overall electrochemical water splitting.

Earth-abundant, low-cost, and highly active bifunctional electrocatalysts are of significant importance to the large-scale production of hydrogen from water electrolysis. Herein, it is reported that novel FeNi 3 /NiFeO x nanohybrids display high electrocatalytic activities in both hydrogen evolution reaction (HER) and oxygen evolution reaction (OER). These FeNi 3 /NiFeO x nanohybrids are obtained with the unique hydrogenation treatment of NiFeO x nanosheets. Small onset potentials of ≈20 and 240 mV are obtained for HER and OER, respectively, benefited from the synergistic effect of FeNi 3 and NiFeO x . Only a small voltage of 1.55 V is needed to reach a current density of 10 mA cm −2 for the overall water splitting in an alkaline electrolyzer when using FeNi 3 /NiFeO x as both cathode and anode catalysts. This is one of the best performance of electrocatalysts for HER and OER, shining the bright future for earth-abundant, low-cost bifunctional electrocatalysts for largescale production of hydrogen from water electrolysis.

10-time lithium rate improvement and 4-time photocatalytic performance enhancement have been achieved with TiO 2 nanocrystals when coated with a thin layer of amorphous carbon from a vacuum decomposition-deposition process. The enhanced performances can be attributed to lower lithium ion diffusion and electronic conduction resistance across the carbon layer into the TiO 2 electrode material and better surface adsorption of the dye molecules and ions. Thus, the current study may provide us an alternative approach in improving the performances of TiO 2 nanocrystals in both lithium ion battery and photocatalysis applications.