Zongqiang Mao

SDC-Carbonate Composite Electrolytes for Low-Temperature SOFCs

Novel composite materials based on mixtures of samarium-doped ceria SDC -carbonate were examined for use as electrolyte materials in low-temperature solid oxide fuel cells LTSOFCs operating at 400-600°C. The composite electrolytes showed high ion conductivity at evaluated temperatures. Composition and calcination temperature were found to affect the morphology and conductivity of the composite electrolytes greatly. During fuel cell operation, water was observed at both electrodes, indicating that the new electrolyte materials conduct both oxygen ions and proton simultaneously. According to fuel cell performance, these composite electrolytes are chemically stable, which is an attractive prospect in LTSOFC applications.

The effect of surface treatments on hydrogen storage of carbon nanotubes

： Carbon nanotubes used in this experiment were grown from a acetylene－ hydrogen mixture on a support using different catalyst precursors. The surface characteristics of carbon nanotubes determined the interaction with hydrogen, so the materials thus produced were submitted to two different treatments, namely nitric acid and alkali solution to gain favorable adsorption surface, these treatments improved surface area and surface activity effectively. At last it can absorb 5％ of hydrogen at room temperature under 10 MPa, and the result is stable.

Measuring hydrogen storage capacity of carbon nanotubes by tangent-mass method

The tangent-mass method is introduced to measure and calculate hydrogen storage capacity of carbon nanotubes by using a high-pressure microbalance. This method can effectively calibrate the effect of buoyancy and conveniently determine the adsorption isotherm. Single-walled carbon nanotubes were measured by this method to provide reference data for future studies.

Operation Conditions Optimization of Hydrogen Production by Propane Autothermal Reforming for PEMFC Application

Autothermal reforming (ATR) is one of the leading methods for hydrogen production from hydrocarbons. Liquefied petroleum gas, with propane as the main component, is a promising fuel for on-board hydrogen producing systems in fuel cell vehicles and for domestic fuel cell power generation devices. In this article, propane ATR process is studied and operation conditions are optimized with PRO/Ⅱ(superscript ®) from SIMSCI for proton exchange membrane fuel cell application. In the ATR system including water gas shift and preferential oxidation, heat in the hot streams and cold streams is controlled to be in balance. Different operation conditions are studied and drawn in contour plots. The region for ATR reforming with the highest efficiency can thus be identified. One operation point was chosen with the following process parameters: feed temperature for the ATR reactor is 425℃, steam to carbon ratio S/C is 2.08, air stoichiometry is 0.256. Thermal efficiency for the integrated system is calculated to be as high as 84.0% with 38.27% H2 and 3.2μl•L^(-1) CO in the product gas.

Hydrogen–air pemfc operation with extraordinarily low gas pressures and internal humidification—conception and experimental prototype stack

Abstract Since the proton exchange membrane (PEM) proved to be the most favourable instrument of mobile fuel cell (FC) development, laboratory work at the Karlsruhe research Center attempted to simplify conditions for PEMFC construction and operation. Air flows were employed in hydrogen fuel cells with low input pressure but high velocity. To avoid external gas humidifiers, porous bipolar plates made of carbon fiber material and containing flow-fields for hydrogen, air and water had been used. A self-made nine-cell stack designed for mobile application was tested within a Chinese–German co-operation. The experiments reveal the characteristics and perspectives of the investigated low-pressure FC system.

Deposition of the platinum crystals on the carbon nanotubes

A new technique and the affecting factors for depositing platinum on the carbon nanotubes were investigated. The results show that the deposited platinum crystals in the atmosphere of hydrogen or nitrogen have a small size and a homogeneous distribution on the surface of the carbon nanotubes. The pretreatment would decrease the platinum particles on the carbon nanotubes significantly.

Analysis and Modeling of Novel Low-Temperature SOFC With a Co-Ionic Conducting Ceria-Based Composite Electrolyte

In recent years, ceria-based composites (CBCs) have been developed as electrolytes for low-temperature solid oxide fuel cells. These materials exhibit extremely high ionic conductivities at 400-600 degrees C. It has also been found that both oxide ion and proton can be conducted in the CBC electrolytes, which makes such co-ionic conducting fuel cell distinct from any other types of fuel cells. In this study, a model involving three charge carriers (oxide ion, proton, and electron) is developed to describe the fuel cell with CBC electrolytes. Various operating characteristics of the fuel cell with CBC electrolytes are investigated, compared to those of the fuel cell with doped ceria electrolytes. The results indicate that the CBC electrolyte behaves as a pure ionic conductor, the cell is more efficient, and a higher output is expected at low temperatures under the same pressure operation than that of the cell with doped ceria electrolytes. [DOI: 10.1115/1.2971173] (Less)

Hydrogen storage by platelet-carbon fibers at room temperature

Abstract In this work, the performance of hydrogen uptake by one special kind of carbon fibers (platelet-vapor grown carbon fibers (VGCFs)) was investigated. The pristine materials are submitted to hydrogen storage without any further treatments. The results show that these materials can absorb ∼4 wt.% of hydrogen at room temperature under ∼9 MPa. The effect of the platelet structure on the adsorption performance of the carbon fibers is highlighted.

A 10kW-scale Distributed Power Plant of Natural Gas-Proton Exchange Membrane Fuel Cell

Abstract A 10 kW-scale natural gas fueled proton exchange membrane fuel cell (PEMFC) distributed power plant is presented in this paper, which is designed for cogeneration of power and heat. With homemade catalysts for CO removal in a two-stage methanation process and integrated reactor in the fuel processing system, the reformed fuel with CO molar fraction less than 10−5 is obtained for the fuel cell stack. Based on Matlab/Simulink/Stateflow and xPC Target platform, a rapid control prototype (RCP) is developed for real-time condition management, signal tracking and parameter tuning, data storing, and man-machine interaction. In a typical running with 4.3 kW stack power, the hydrogen production efficiency, gross power generation efficiency and heat recovery efficiency approach to 76%, 41% and 50%, respectively. The peak stack power reaches 7.3 kW. Though there is still considerable distance to long-term operation at 10 kW-scale net power generation, it is a milestone for the PEMFC-based stationary application in China.

Proton Exchange Membrane Fuel Cell with Humidifying Zone

Water management is of great importance to maintain performance and durability of proton exchange membrane fuel cells. This paper presents a novel proton exchange membrane (PEM) fuel cell with a humidification zone in the membrane electrode assembly (MEA) of each cell, in which the moisture of the cathode exhaust gas could transfer through the membrane to humidify anode or cathode dry gas. With a simple model, the relative humidity (RH) of the dry air exhaust from a membrane humidifier with 100% RH stream as a counter flow is calculated to be 60.0%, which is very close to the experimental result (62.2%). Fuel cell performances with hydrogen humidifying, air humidifying and no humidifying are compared at 50, 60 and 70°C and the results indicate that humidifying is necessary and the novel design with humidifying zone in MEA is effective to humidify dry reactants. The hydrogen humidifying shows better performance in short term, while water recovered is limited and the stability is not as good as air humidifying. It is recommended that both air and hydrogen should be humidified with proper design of the humidifying zones in MEA and plates.