A chloroplast structured photocatalyst enabled by microwave synthesis.

Photosynthesis occurs through the synergistic effects of the non-ncontinuously distributed components in the chloroplast. Inspired by nature, we mimic chloroplast and develop a generic approach to synthesize non-continuously distributed semiconductors threaded by carbon nanotubes. In the synthesis, carbon nanotubes serve as microwave antennas to produce local super-hot dots on the surface, which might induce and accelerate various organic/inorganic semiconductors assembly. With the unique nanoscale designed bionic architecture, a chloroplast structured photocatalyst with 3-dimentional dual electron transfer pathways facilitate enhanced photocatalytic performance. The as-synthesized carbon nanotubes-titanium oxide achieves a record-breaking efficiency of 86% for nitric oxide treatment under ultraviolet light irradiation. As a general strategy, a wide variety of carbon nanotubes threaded chloroplast structured nanomaterials can be synthesized and these nanomaterials could find applications in energy chemistry, environmental science and human health.

Microwave-antenna induced in situ synthesis of Cu nanowire threaded ZIF-8 with enhanced catalytic activity in H2 production.

A microwave-antenna strategy was developed for the in situ synthesis of Cu nanowire (CuNW) threaded ZIF-8. The CuNWs acted as microwave-antennas to generate surface "super hot" dots. The high temperature of "super hot" dots induced adsorption and coordination of metal ions and organic ligands, followed by in situ assembly and crystal-growth along the CuNWs. This catalyst exhibited high activity and stability in H2 production via NH3BH3 hydrolysis owing to the synergetic effect. The CuNWs supplied a rapid electron transfer channel while ZIF-8 assembled on the CuNWs offered a large capacity for adsorbing reactants and channels for rapidly transferring H(-)/H(+) ions toward Cu active sites. Other one-dimensional threaded MOFs, including CuNW threaded MOF-5 and UIO-66, or carbon nanotube threaded ZIF-8 and ZIF-67 could also be prepared using the microwave-antenna strategy.

CNTs threaded (001) exposed TiO2 with high activity in photocatalytic NO oxidation.

A microwave-ionothermal strategy was developed for in situ synthesis of CNTs threaded TiO2 single crystal with a tunable percentage of surface exposed (001) active facets. The CNTs were used as microwave antennas to create local "super hot" dots to induce Ti(3+) adsorption and hydrolysis, thereby leading to a good assembly of (001) facets exposed single crystalline TiO2 threaded by the CNTs in the presence of Hmim[BF4] ionic liquid. Due to the high percentage of the active (001) facets of single crystal TiO2 and the direct electron transfer property of the CNTs, the as-prepared CNTs-TiO2 composite showed a photocatalytic NO removal ratio of up to 76.8% under UV irradiation. In addition, with self-doped Ti(3+), the CNTs-TiO2 composite also exhibited an enhanced activity under irradiation with either solar lights or visible lights, showing good potential in practical applications for environmental remediation.

Highly efficient and stable Au/CeO2-TiO2 photocatalyst for nitric oxide abatement: potential application in flue gas treatment.

In the present work, highly efficient and stable Au/CeO2-TiO2 photocatalysts were prepared by a microwave-assisted solution approach. The Au/CeO2-TiO2 composites with optimal molar ratio of Au/Ce/Ti of 0.004:0.1:1 delivered a remarkably high and stable NO conversion rate of 85% in a continuous flow reactor system under simulated solar light irradiation, which far exceeded the rate of 48% over pure TiO2. The tiny Au nanocrystals (∼1.1 nm) were well stabilized by CeO2 via strong metal-support bonding even it was subjected to calcinations at 550 °C for 6 h. These Au nanocrystals served as the very active sites for activating the molecule of nitric oxide and reducing the transmission time of the photogenerated electrons to accelerate O2 transforming to reactive oxygen species. Moreover, the Au-Ce(3+) interface formed and served as an anchoring site of O2 molecule. Then more adsorbed oxygen could react with photogenerated electrons on TiO2 surfaces to produce more superoxide radicals for NO oxidation, resulting in the improved efficiency. Meanwhile, O2 was also captured at the Au/TiO2 perimeter site and the NO molecules on TiO2 sites were initially delivered to the active perimeter site via diffusion on the TiO2 surface, where they assisted O-O bond dissociation and reacted with oxygen at these perimeter sites. Therefore, these finite Au nanocrystals can consecutively expose active sites for oxidizing NO. These synergistic effects created an efficient and stable system for breaking down NO pollutants. Furthermore, the excellent antisintering property of the catalyst will allow them for the potential application in photocatalytic treatment of high-temperature flue gas from power plant.

Copper Nanowires: A Substitute for Noble Metals to Enhance Photocatalytic H2 Generation.

Microwave-assisted hydrothermal approach was developed as a general strategy to decorate copper nanowires (CuNWs) with nanorods (NRs) or nanoparticles (NPs) of metal oxides, metal sulfides, and metal organic frameworks (MOFs). The microwave irradiation induced local "super hot" dots generated on the CuNWs surface, which initiated the adsorption and chemical reactions of the metal ions, accompanied by the growth and assembly of NPs building blocks along the metal nanowires' surfaces. This solution-processed approach enables the NRs (NPs) @CuNWs hybrid structure to exhibit three unique characteristics: (1) high coverage density of NRs (NPs) per NWs with the morphology of NRs (NPs) directly growing from the CuNWs core, (2) intimate contact between CuNWs and NRs (NPs), and (3) flexible choices of material composition. Such hybrid structures also increased light absorption by light scattering. In general, the TiO2/CuNWs showed excellent photocatalytic activity for H2 generation. The corresponding hydrogen production rate is 5104 µmol h(-1) g(-1) with an apparent quantum yield (AQY) of 17.2%, a remarkably high AQY among the noble-metal free TiO2 photocatalysts. Such performance may be associated with the favorable geometry of the hybrid system, which is characterized by a large contact area between the photoactive materials (TiO2) and the H2 evolution cocatalyst (Cu), the fast and short diffusion paths of photogenerated electrons transferring from the TiO2 to the CuNWs. This study not only shows a possibility for the utilization of low cost copper nanowires as a substitute for noble metals in enhanced solar photocatalytic H2 generation but also exhibits a general strategy for fabricating other highly active H2 production photocatalysts by a facile microwave-assisted solution approach.