High-quality mesoporous graphene particles as high-energy and fast-charging anodes for lithium-ion batteries.

The application of graphene for electrochemical energy storage has received tremendous attention; however, challenges remain in synthesis and other aspects. Here we report the synthesis of high-quality, nitrogen-doped, mesoporous graphene particles through chemical vapor deposition with magnesium-oxide particles as the catalyst and template. Such particles possess excellent structural and electrochemical stability, electronic and ionic conductivity, enabling their use as high-performance anodes with high reversible capacity, outstanding rate performance (e.g., 1,138 mA h g-1 at 0.2 C or 440 mA h g-1 at 60 C with a mass loading of 1 mg cm-2), and excellent cycling stability (e.g., >99% capacity retention for 500 cycles at 2 C with a mass loading of 1 mg cm-2). Interestingly, thick electrodes could be fabricated with high areal capacity and current density (e.g., 6.1 mA h cm-2 at 0.9 mA cm-2), providing an intriguing class of materials for lithium-ion batteries with high energy and power performance

Multi-functional anodes boost the transient power and durability of proton exchange membrane fuel cells.

Proton exchange membrane fuel cells have been regarded as the most promising candidate for fuel cell vehicles and tools. Their broader adaption, however, has been impeded by cost and lifetime. By integrating a thin layer of tungsten oxide within the anode, which serves as a rapid-response hydrogen reservoir, oxygen scavenger, sensor for power demand, and regulator for hydrogen-disassociation reaction, we herein report proton exchange membrane fuel cells with significantly enhanced power performance for transient operation and low humidified conditions, as well as improved durability against adverse operating conditions. Meanwhile, the enhanced power performance minimizes the use of auxiliary energy-storage systems and reduces costs. Scale fabrication of such devices can be readily achieved based on the current fabrication techniques with negligible extra expense. This work provides proton exchange membrane fuel cells with enhanced power performance, improved durability, prolonged lifetime, and reduced cost for automotive and other applications

Material and Device Design for Rapid Response and Long Lifetime Proton Exchange Membrane Fuel Cells (PEMFCs)

Proton exchange membrane fuel cells (PEMFCs) have been regarded as the most promising candidate for fuel cell vehicles and tools. Their broader adaption, however, has been impeded by cost and lifetime, as well as the inability to respond to fluctuations associated with operation conditions, fuel supply, and transient load. In this dissertation, a novel strategy to improve the performance and durability of PEMFCs for automotive application is purposed. Unlike the conventional hybrid strategies, which batteries or capacitors are always integrated with the fuel cell to achieve high fuel efficiency and high-power output, the novel fuel cell is integrated with energy-storage materials to form a hybrid device. Tungsten oxide is proved to be a promising energy-storage material using in the PEMFC application, which has high chemical stability and excellent electrochemical performance in the fuel cell configuration. By integrating a thin layer of tungsten oxide (WO3) within the anodes, novel PEMFCs shows significantly enhanced power performance for transient operation, as well as improved durability against adverse operating conditions. Meanwhile, the enhanced power performance minimizes the use of auxiliary energy-storage systems and reduces costs. In addition, the mechanisms of degradation of PEMFCs, as well as the working principles of WO3 in the hybrid cell are studied. The WO3 layer in the hybrid cell serves as a rapid-response hydrogen reservoir, oxygen scavenger, sensor for power demand, and regulator for hydrogen-disassociation reaction, effectively stabilize the anode potential and inhibit rising of the anode potential during the transient conditions

The Hydrothermal Stability and the Properties of Non- and Strongly-Interacting Rh Species over Rh/γ, θ-Al2O3 Catalysts

The present work reports the effects of γ-, θ-phase of alumina on the hydrothermal stability and the properties of non- and strongly-interacting Rh species of the Rh/Al2O3 catalysts. Comparing to γ-Al2O3, θ-Al2O3 can not only reduce the amount of occluded Rh but also better stabilize Rh during hydrothermal aging treatment. When the aging time was prolonged to 70 h, all the non-interacting Rh was transformed into strongly-interacting Rh and occluded Rh. The XPS results indicated that non- and strongly-interacting Rh might exist in the form of Rh/Rh3+ and Rh4+, respectively. CO-NO reaction was chosen as a probe reaction to research more information about non- and strongly-interacting Rh. The two Rh species had similar apparent activation energy (Eapp) of 170 kJ/mol, which indicated that non- and strongly-interacting Rh follow the same reaction path. The non-interacting Rh was removed from aged samples by the acid-treated method, and obtained results showed that only 2.5% and 4.0% non-interacting Rh was maintained in aged Rh/γ-Al2O3 and Rh/θ-Al2O3

Multi-functional anodes boost the transient power and durability of proton exchange membrane fuel cells.

Proton exchange membrane fuel cells have been regarded as the most promising candidate for fuel cell vehicles and tools. Their broader adaption, however, has been impeded by cost and lifetime. By integrating a thin layer of tungsten oxide within the anode, which serves as a rapid-response hydrogen reservoir, oxygen scavenger, sensor for power demand, and regulator for hydrogen-disassociation reaction, we herein report proton exchange membrane fuel cells with significantly enhanced power performance for transient operation and low humidified conditions, as well as improved durability against adverse operating conditions. Meanwhile, the enhanced power performance minimizes the use of auxiliary energy-storage systems and reduces costs. Scale fabrication of such devices can be readily achieved based on the current fabrication techniques with negligible extra expense. This work provides proton exchange membrane fuel cells with enhanced power performance, improved durability, prolonged lifetime, and reduced cost for automotive and other applications

Hierarchical Nanostructured WO₃ with Biomimetic Proton Channels and Mixed Ionic-Electronic Conductivity for Electrochemical Energy Storage

Protein channels in biologic systems can effectively transport ions such as proton (H⁺), sodium (Na⁺), and calcium (Ca⁺) ions. However, none of such channels is able to conduct electrons. Inspired by the biologic proton channels, we report a novel hierarchical nanostructured hydrous hexagonal WO₃ (<i>h</i>-WO₃) which can conduct both protons and electrons. This mixed protonic–electronic conductor (MPEC) can be synthesized by a facile single-step hydrothermal reaction at low temperature, which results in a three-dimensional nanostructure self-assembled from <i>h</i>-WO₃ nanorods. Such a unique <i>h</i>-WO₃ contains biomimetic proton channels where single-file water chains embedded within the electron-conducting matrix, which is critical for fast electrokinetics. The mixed conductivities, high redox capacitance, and structural robustness afford the <i>h</i>-WO₃ with unprecedented electrochemical performance, including high capacitance, fast charge/discharge capability, and very long cycling life (>50 000 cycles without capacitance decay), thus providing a new platform for a broad range of applications