Direct Hydrocarbon Low-temperature Fuel Cell

The development of fuel cell technology focuses mainly on the use of hydrogen as fuel or carrier of energy for its operation. However, there are many limitations associated with the hydrogen fuel: pure hydrogen production is expensive and time-consuming; storage and dispensing are much difficult; it is highly inflammable and not easy to integrate into the existing oil and gas infrastructure. In this regard, the use of liquid hydrocarbons, for example, methanol, ethanol, formic acid, ethylene glycol, and glucose directly as a fuel in the fuel cell has certain advantages. The high energy density of<!--hydrocarbon fuel-->hydrocarbon fuel, the cheap and minimum requirement of subsystem assembly with no reformer, easy and safe handling of hydrocarbons in contrast to hydrogen are the main reasons for potential use as fuel in a fuel cell to power portable devices. Based on the hydrocarbons used directly as fuel, they are named as direct methanol fuel cell (DMFC),<!--direct ethanol fuel cell-->direct ethanol fuel cell (DEFC), direct ethylene glycol fuel cell (DEGFC), direct formic acid fuel cell (DFAFC), and direct glucose fuel cell (DGFC). Most of such fuel cell technologies are developed on proton exchange-based electrolytes, but it is well known that it is easy to oxidize bulkier hydrocarbon in alkaline electrolyte. The development of various catalysts for direct oxidation of hydrocarbons at anode and oxygen reduction reaction at the cathode and electrochemical transport processes associated with a direct hydrocarbon fuel cell at low temperature are discussed. Different noble and nonnoble anode and cathode catalysts are also included in the discussion. A comparative study of efficiency of different hydrocarbons as fuel in proton exchange membrane (PEM) and anion exchange membrane (AEM) fuel cells is revealed, whereasDMFC based on PEM electrolyte is most developed, there is further scope for improvement in efficiency forAEM-based direct fuel cells having certain advantages such as minimum crossover of fuel, easy oxidation of fuel at anode, and so on. The scope of further improvement in different types of the direct hydrocarbon fuel cell is discussed from the point of different perspectives, for example, market demand and cost, usefulness, environmental benefit, portability, and miniaturization.