Based On 3D Graphene Aerogels Heteroatom Doping Hybrid Materials As Efficient Oxygen Electrode Catalyst

Due to the gradual depletion of conventional energy sources, increasing demand has stimulated intensive research on alternative energy conversion and storage systems that are highly efficient, low-cost, and environmentally friendly. Electrocatalysts for the oxygen reduction reaction（ORR） and oxygen evolution reaction（OER） are critical for various energy technologies, including fuel cells, metal-air batteries and water splitting, while primary metal-air batteries and fuel cells depend on the ORR at the cathodes to function, water splitting for oxygen production may be accomplished by utilizing the OER. A major step forward from these conventional technologies is to develop bi-functional catalyst materials that can perform both ORR and OER with very low overpotentials. As is well-known, platinum（Pt） performs very well for the ORR（and performs poorly for the OER）; ruthenium oxide（RuO2） and iridium oxide（IrO2） perform very well for the OER（and perform poorly for the ORR）. Although the hybrids of Pt（or Pt alloys） and these metal oxides（RuO2 and IrO2） can serve as highly active bi-functional catalysts for both ORR and OER, these precious metals are among the rarest elements on earth and, hence, are not practical for large-scale applications. Herein, one efficient non-noble-metal catalyst for ORR and OER, denoted Co₃O₄/N-GAs, and one efficient non-metal catalyst for ORR, abbreviated as N, B-GAs. These two catalysts have been obtained by one-step hydrothermal assembly of graphene oxide with chitosan or glucose. The morphology of the composites was analyzed by scanning electron microscopy（SEM）, transmission electron microscopy（TEM）. Cyclic voltammetry（CV）, rotating disk electrode（RDE）, rotating ring-disk electrode（RRDE） and chronoamperometric measurements were utilized to evaluate the electrocatalytic performance of the 3D heteroayom doped graphene aerogels. The results showed that the proposed Co₃O₄/N-GAs exhibits an excellent catalytic performance towards ORR and OER. N, B-GAs exhibits an outstanding catalytic activity for the oxygen reduction reaction（ORR）. Furthermore, the as-prepared catalysts possess better tolerance to methanol crossover and excellent stability, which catalyze oxygen to H2 O through an efficient four-electron pathway. The enhanced electrocatalytic performance could be chiefly attributed to the large specific surface area and 3D interconnected framework of the obtained hybrids, intriguing properties of graphene and synergistic effect of multi-components.