Electrocatalytic Oxygen Reduction by Dopant‐free, Porous Graphene Aerogel

Abstract

Porous graphene aerogel (GA) was prepared by the hydrothermal reduction of graphene oxide (GO). The prepared GA was characterized with the various analytical techniques. Its morphological and electrochemical properties were investigated and compared with those of GO and electrochemically reduced graphene oxide (erGO). Three glassy carbon (GC) electrodes modified with GO, erGO, and GA were employed to study the electrocatalytic oxygen reduction reaction (ORR). The influence of GA porosity on the kinetic parameters of the ORR was also investigated. Whereas two‐electron transfer ORR was observed at the erGO‐ and GO‐modified electrodes, the GA‐modified electrode exhibited drastically enhanced electrocatalytic ORR activity. The remarkable electrocatalytic activity of GA can be attributed to the unique porous effect of GA. The porous GA offers confined spaces for ORR that would drastically increase the residence time of oxygen and thus enhance the contact frequency for the reduction of oxygen. Additional rotating disk electrode voltammetry corroborates that the porous GA facilitates efficient ORR.

Graphene aerogels via hydrothermal gelation of graphene oxide colloids: Fine-tuning of its porous and chemical properties and catalytic applications

“…The un-doped graphene aerogel is reported to provide four electron reduction for ORR, showing higher activity in alkaline media than GO or electrochemically reduced GO (erGO). [94] The confined space provided by the porous GA is claimed to greatly increase the residence time of O2 on the electrode, facilitating ORR by a highly efficient electron transfer pathway that apparently differs from the ORR mechanisms in GO and erGO. Nevertheless, the most active aerogels in the literature are those doped with heteroatoms mainly nitrogen [95,96] but also other heteroatoms such as boron or phosphorous [97] or combinations thereof either ternary or binary.…”

Modificação de catalisadores de carbono amorfo com óxidos mistos de Nb, Zr, Mo e Pd para a eletrossíntese de peróxido de hidrogênio (H>sub<2>/sub<O>sub<2>/sub<)

“…Também é sugerido que a reação ( 16) ocorra com potenciais mais baixos e a reação posterior com potenciais mais altos. Para o processo posterior, recentemente foi sugerido que, para potenciais mais altos, a ORR pode ocorrer pela transferência eletrônica de esfera interna (ISET), que é a reação com a molécula de oxigênio adsorvida no local ativo do catalisador ou pela transferência eletrônica de esfera externa (OSET) que a molécula de oxigênio é estável na planície externa de Helmholtz e pode capturar um elétron para acompanhar a redução ao peróxido de hidrogênio [31,90]. A combinação desses efeitos pode explicar o efeito observado anteriormente da via "dois mais dois" para a redução de oxigênio, que é uma combinação geral de efeitos em diferentes faixas de potencial.…”