No abstract

A novel anode thermal optimization approach is presented and developed in this paper, based on the detailed investigations of operating temperature on the performance of passive micro direct methanol fuel cell (μDMFC). First, a two‐dimensional model of two‐phase cell is established to observe methanol solution transport and pressure distribution under different operating temperatures. Moreover, passive stainless steel‐based μDMFC preparation and fabrication use micro laser‐cut technology, and the influences of cell temperature on corresponding cell performances are under experimental investigation. Eventually, according to the consequences of simulation and experimental analysis, a practical anode self‐adaptive thermal control strategy equips with the self‐made silicone heating sheet is designed, and the stable work of μDMFC at the optimal temperature is realized through this method. Compared with the conventional fuel cell, the optimized fuel cell system can significantly improve the net output power density and efficiency (Power density increased from 20.8 mW cm−2 to 52.16 mW cm−2).

To achieve a self-adaptive fuel supply mechanism for the micro direct methanol fuel cell (μDMFC), we designed and developed a thermal control microvalve channel structure, where we considered the relationship between the temperature characteristics, viscosity, and velocity of the methanol solution. Both the single channel model and three-dimensional cell model for the microvalve were established using the COMSOL Multiphysics program. The results demonstrated that in the microvalve channel, the viscosity of the solution decreased, and the flow rate at the microvalve outlet increased with the increasing temperature. Meanwhile, the geometry structure of the microvalve single channel was optimized, so that the effect of the control speed of the microvalve under temperature changes became more prominent. In the full-cell model analysis, a low-velocity methanol solution at the low current density can significantly inhibit methanol crossover. At the high current densities, an increase in the methanol solution flow rate was beneficial to an increase in the cell reaction output. The μDMFC was fabricated and the experiment was conducted, where the results showed that the power density of the self-adaptive cell reached a maximum value of 16.56 mW/cm2 in 2 M methanol solution, which was up to 7% better than conventional cell performance. The proposed microvalve structure can effectively improve the output power of the μDMFC during the whole reaction process, and it may improve the stability of the cell operation.

As a new energy technology, the fuel cell has developed rapidly, and its performance has been continuously improved. Fuel cell stacks composed of multiple single cells are gradually being used in portable electronic products. Since the performance of fuel cells cannot be optimal at room temperature, it is critical to research cell temperature characteristics and heat distributions in applications. In this paper, the effects of temperature and charge transfer coefficient and the relationship between exchange current density and output voltage were analyzed by the mathematical model of direct methanol fuel cells. Moreover, to optimize the thermal layout of the fuel cell stack in the printed circuit board (PCB) substrate, the idea of a fuel cell as a device was proposed innovatively, and the corresponding thermal optimization strategy was analyzed. A novel particle swarm optimization algorithm was used to detect the optimal layout of fuel cells of different specifications on the same substrate. The three-dimensional thermal simulation model was used to obtain the temperature data and verify the optimization results.

Semiconductor gas sensors are widely used in the fields of health, safety, energy efficiency, and emission control owing to their high sensitivity, low power consumption, and small size. Among them, the thin film‐based semiconductor gas sensors have excellent sensing characteristics due to their controllable morphology and large specific surface area, which can effectively improve the sensitivity of the gas sensors and shorten the response and recovery time. Gas–liquid interfacial self‐assembly method is an effective method for fabricating thin films, which can be utilized to construct large wafer‐scale thin films on the liquid surface. In this review, the advantages of thin films prepared by gas–liquid interfacial self‐assembly method are introduced. Subsequently, the recent progress in the preparation of thin films by gas–liquid interfacial self‐assembly method and their applications in semiconductor gas sensors are reviewed and summarized, mainly from two aspects of organic materials and inorganic materials. In the end, the technology is prospected, and it is considered that there is still much room for improvement and optimization in the future.