Hydrogen burning fuel cells

In the aforementioned studies, Coors and Kreuer bring up the issue of mixed proton-oxide ion conduction of BaCeOs-based materials while proton conduction is beneficial for efficiency in hydrogen-burning fuel cells, some oxide ion transport is beneficial for providing water vapor on the anode side for reforming and shifting carbon-based fuels such as methane. 

The hydrogen-oxygen fuel cell also burns hydrogen in a sense, but the burning is controlled so that most of the chemical energy is converted to electrical energy, not to heat. 

The theoretical maximum energy available as electric energy in any electrochemical cell is equal to AjC for the reaction. The maximum energy release when a fuel is burned is Aj.H°. One of the measures used to evaluate a fuel cell is the efficiency value, e = A,.G°/Aj.H°. For the hydrogen-oxygen fuel cell, e = -474.4 kj morV-571.6 kj mol" = 0.83. 

Hydrogen can be used with vei y little or no pollution for energy applications. When hydrogen is burned in air, the main combustion product is water, with traces of nitrogen oxides. Wlien hydrogen is used to produce electricity in a fuel cell, the only emission is water vapor. 

Unlike burning hydrogen in air, in a fuel cell the electrolyte partitions the overall reaction into half-cell reactions on either side of the cell. 

Hydrogen, a fuel that releases a large amount of chemical energy when it bums, is used as an energy source in fuel cells. Use standard enthalpies of formation to calculate the change in mass that occurs when 1.00 mol of H2 is burned. 

Hydrogen gas is odorless and colorless. It burns almost invisibly and a fire may not be readily detected. Compressed hydrogen gas could be ignited with the static discharge of a cell phone. But, an accident may not cause an explosion, since carbon fiber reinforced hydrogen tanks are nearly indestructible. There is always the danger of leaks in fuel cells, refineries, pipelines and fueling stations. 

An onboard hydrogen tank has several problems since hydrogen leaks easily, is hard to store and hard to compress and burns quickly. Overcoming all these concerns has been expensive but most of the major auto companies has solved these problems for the most part in their prototype fuel cell vehicles. Refueling tends to be difficult although there are now a number of hydrogen refueling stations in use around the world. 

However, burning hydrogen is less desirable than using it in a fuel cell. The direct combustion of hydrogen releases carbon monoxide, hydrocarbons and some particulates, although these are only about 0.1 of that from the burning of fossil fuels. 

The biggest attraction of fuel-cell-powered vehicles for car manufacturers is the fact that they no longer emit nitrogen oxides or hydrocarbons (or carbon dioxide if they are fuelled with pure hydrogen). (Burning hydrogen in internal combustion engines results in NOx emissions fuel-cell vehicles emit only water.) This effectively does away with one of the main environmental discussion points about traffic. In California, these zero-emission cars have been demanded since the foundation of the California Fuel Cell Partnership in 1999. 

About 70 percent of the hydrogen is converted to electricity in the fuel cell stack, and the tail gas is then burned to generate heat which is transferred via a glycol/water loop to the steam generator. The same loop passes through the cooling plates or the fuel cell to remove heat. 

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