Fuel cells: Materials needs and advances

Fuel cells are highly efficient electrochemical energy-conversion devices with a wide application potential, spanning from portable power sources to stationary power generation. They are typically categorized according to their operating temperature, for example, low temperature (<100 degrees C), intermediate temperature (450-800 degrees C) and high temperature (>800 degrees C). Recently, reduced temperature fuel cells operating at 200-400 degrees C have also received considerable attention for their multiple benefits. A single fuel cell is composed of a porous anode for fuel oxidation, a dense electrolyte for ion transportation, and a porous cathode for oxygen reduction. Due to their different functions and operating environments, each layer of the cell faces unique materials requirements in terms of ionic and electronic conductivity, chemical and mechanical stability, thermal expansion, etc. This article gives a thorough perspective on the challenges and recent advances in anode, electrolyte, and cathode materials for the various types of fuel cells. Emerging fuel cells operating at 200-400 degrees C are also discussed and commented. Finally, the key areas of need and major opportunities for further research in the field are outlined.