Facile oxygen reduction on a three-dimensionally ordered macroporous graphitic C3N4/carbon composite electrocatalyst
One of the greatest stumbling blocks hindering broad applications of fuel cells is the high cost and vulnerability of the platinum catalyst as well as the sluggish oxygen reduction reaction (ORR) on the cathode. Although Pt alloys or nonnoble metals have been developed as substitute catalysts for the ORR, they still suffer from multiple disadvantages, such as low stability under fuel cell conditions, vulnerability to fuel crossover, and harmfulness to the environment. Thus, the ongoing search for metal-free catalysts for the ORR has attracted much attention. In this regard, nitrogen-containing carbon materials are of particular interest owing to their catalytic activity towards the ORR brought about by nitrogen incorporation, which has been confirmed by both experimental studies and quantum-mechanical calculations. Among these materials, graphitic carbon nitride (g-C3N4) is especially promising because of its high nitrogen content, low cost, and easily tailorable structure, which makes it potentially suitable for oxygen reduction as well as other applications, such as photocatalysis or hydrogen storage, under mild conditions.