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Superior gas capture and detection performance play an important role in gas sensing materials. Effects of atomic vacancy defects on intrinsic properties of material are also not negligible. Here we firstly discuss gas adsorption behavior of defective 1T’ WS2 monolayer. We take toxic NO2 gas as an example to compare adsorption effects between defective and perfect 1T'WS2 monolayer. First-principles study based on density functional theory(DFT) is carried out to act as the theoretical basis. These results demonstrate vacancy defects could enhance adsorption stability of 1T’ WS2 monolayer, which provide lower adsorption energy, more charge transfer and more overlaps of density of states. Therefore, vacancy defects make 1T’ WS2 monolayer possess more outstanding surface activity and adsorption performance. This can also offer theoretical support for the improvement of nanomaterials applied in those high performance gas sensing devices.

Different anode flow fields of air-breathing micro direct methanol fuel cells (@mDMFCs) are investigated to improve the cell performances. The single-serpentine flow field can effectively improve the methanol mass transport efficiency and exhibit higher exhaust resultant (CO"2) rates than other flow fields such as gird, parallel and double-serpentine. Additionally, the effects of open ratios and channel lengths on the cell performance are evaluated to determine the optimal anode flow field structures. The @mDMFCs with different anode flow fields are fabricated using silicon-based micro-electro-mechanical systems (MEMS) technologies and are tested at room temperature. The experimental results show that the single-serpentine flow field exhibits a significantly higher performance than those of other flow fields, demonstrating 16.83mWcm^-^2 in peak power density and a substantial increase in mass transport coefficients. Moreover, for optimum single-serpentine flow field, it is appropriate for the flow channel dimensions to be in the ratio of 2:3:254 for channel width: ridge width: channel length.

In this paper, a novel micro-direct methanol fuel cell (@m-DMFC) with a CNT-MEA compound structure is purposed for water management. The CNT paper as water transmittal layer is sandwiched between the gas diffusion layer (GDL) and cathode current collector. This new water transmittal layer can passively prevent flooding in the cathode avoiding parasitic power loss and ensure efficiency of oxygen mass transport by humidify dry oxygen. The CNT paper is fabricated by aggregate of carbon nanotubes filtering mixture suspension of MWNTs and Triton X-100 surfactant and the other components of @m-DMFC with a CNT-MEA are produced using MEMS technologies. To analyze the performance of @m-DMFC with a CNT-MEA compound structure, all the experiments are fed with 3.0M methanol solution and flow rates of 1ml/min at a temperature of 40^oC. The experiment result shows that the @m-DMFC with CNT-MEA exhibits significantly higher performance than the conventional @m-DMFC without CNT-MEA, showing the peak power density is 46mWcm^-^2. Moreover, during the long-term operation of the @m-DMFC with CNT-MEA, there is no water flooding on the cathode surface. Therefore, our water management system achieves the goal of performance enhancement without introducing parasitic losses.