Energy storage applications of activated carbons: supercapacitors and hydrogen storage

Porous carbons have several advantageous properties with respect to their use in energy applications that require constrained space such as in electrode materials for supercapacitors and as solid state hydrogen stores. The attractive properties of porous carbons include, ready abundance, chemical and thermal stability, ease of processability and low framework density. Activated carbons, which are perhaps the most explored class of porous carbons, have been traditionally employed as catalyst supports or adsorbents, but lately they are increasingly being used or find potential applications in the fabrication of supercapacitors and as hydrogen storage materials. This manuscript presents the state-of-the-art with respect to the preparation of activated carbons, with emphasis on the more interesting recent developments that allow better control or maximization of porosity, the use of cheap and readily available precursors and tailoring of morphology. This review will show that the renewed interest in the synthesis of activated carbons is matched by intensive investigations into their use in supercapacitors, where they remain the electrode materials of choice. We will also show that activated carbons have been extensively studied as hydrogen storage materials and remain a strong candidate in the search for porous materials that may enable the so-called Hydrogen Economy, wherein hydrogen is used as an energy carrier. The use of activated carbons as energy materials has in the recent past and is currently experiencing rapid growth, and this review aims to present the more significant advances.