Changlong Xiao

Nanostructured photoelectrochemical solar cell for nitrogen reduction using plasmon-enhanced black silicon.

Ammonia (NH3) is one of the most widely produced chemicals worldwide. It has application in the production of many important chemicals, particularly fertilizers. It is also, potentially, an important energy storage intermediate and clean energy carrier. Ammonia production, however, mostly uses fossil fuels and currently accounts for more than 1.6% of global CO2 emissions (0.57  Gt in 2015). Here we describe a solar-driven nanostructured photoelectrochemical cell based on plasmon-enhanced black silicon for the conversion of atmospheric N2 to ammonia producing yields of 13.3 mg m−2 h−1 under 2 suns illumination. The yield increases with pressure; the highest observed in this work was 60 mg m−2 h−1 at 7 atm. In the presence of sulfite as a reactant, the process also offers a direct solar energy route to ammonium sulfate, a fertilizer of economic importance. Although the yields are currently not sufficient for practical application, there is much scope for improvement in the active materials in this cell.

MnO2/MnCo2O4/Ni heterostructure with quadruple hierarchy: a bifunctional electrode architecture for overall urea oxidation

A three-dimensional MnO2/MnCo2O4/Ni core–shell heterostructured electrode has been fabricated through a facile method. This electrode architecture consists of four levels of interconnected hierarchy: a primary macroporous Ni foam scaffold (≥500 μm), an intermediate vertically-aligned MnCo2O4 core-nanoflake array (50–100 nm), topmost ultra-thin MnO2 nanosheets (∼10 nm) and short-range ordered mesopores (∼5 nm) on the MnO2 nanosheets. This freestanding, hierarchical porous electrode has advantages in enhancing electroactive surface area, enabling efficient mass transport through the porous structure. The heterostructured electrode exhibits a low onset potential (1.33 V vs. RHE), a high anodic peak current density (1000 mA cm−2 g−1 at 1.7 V vs. RHE) and long-term catalytic stability for urea oxidation, which surpasses previous reported electrode materials for urea electrolysis. Remarkably, the MnO2/MnCo2O4/Ni electrode possesses bifunctional catalytic activity for both urea oxidation and hydrogen evolution. A urea electrolytic cell with both anode and cathode using the heterostructured electrodes has been fabricated and a current density of 10 mA cm−2 has been achieved at a cell voltage of 1.55 V. This noble metal-free quadruple hierarchy electrode shows potential as a new platform for multi-purpose applications.

In-Situ-Activated N-Doped Mesoporous Carbon from a Protic Salt and Its Performance in Supercapacitors

Protic salts have been recently recognized to be an excellent carbon source to obtain highly ordered N-doped carbon without the need of tedious and time-consuming preparation steps that are usually involved in traditional polymer-based precursors. Herein, we report a direct co-pyrolysis of an easily synthesized protic salt (benzimidazolium triflate) with calcium and sodium citrate at 850 °C to obtain N-doped mesoporous carbons from a single calcination procedure. It was found that sodium citrate plays a role in the final carbon porosity and acts as an in situ activator. This results in a large surface area as high as 1738 m2/g with a homogeneous pore size distribution and a moderate nitrogen doping level of 3.1%. X-ray photoelectron spectroscopy (XPS) measurements revealed that graphitic and pyridinic groups are the main nitrogen species present in the material, and their content depends on the amount of sodium citrate used during pyrolysis. Transmission electron microscopy (TEM) investigation showed that sodium citrate assists the formation of graphitic domains and many carbon nanosheets were observed. When applied as supercapacitor electrodes, a specific capacitance of 111 F/g in organic electrolyte was obtained and an excellent capacitance retention of 85.9% was observed at a current density of 10 A/g. At an operating voltage of 3.0 V, the device provided a maximum energy density of 35 W h/kg and a maximum power density of 12 kW/kg.

Controllable fabrication of heterostructured Au/Bi2O3 with plasmon effect for efficient photodegradation of rhodamine 6G

ABSTRACT Three-dimensional (BiO)2CO3 (BSC) nanostructures were synthesised by a hydrothermal reaction, and Bi2O3 nanoparticles were then obtained by calcining BSC precursor at different temperatures. BSC and Bi2O3 samples were then sputtering coated with Au to get the resultant Au/BSC and Au/Bi2O3 for the investigation of the effect of the Au coating on the photocatalytic performance of the samples. The phase structure, morphology and composition of the samples were characterised by X-ray diffraction, scanning electron microscopy and energy-dispersive spectroscopy (EDS). UV–vis diffuse reflectance spectra were used to measure the response of different catalysts to UV–vis light. The photocatalytic activity was investigated for the degradation of rhodamine 6G at room temperature and the light intensity was 1 sun. Bi2O3 exhibited better photocatalytic performance than BSC due to the narrow band gap of Bi2O3, and the coating of Au also endowed the samples with higher photocatalytic capability as compared to the bare one.