Highly Active Bifunctional Oxygen Electrocatalytic Sites Realized in Ceria–Functionalized Graphene

Abstract

The development of efficient, durable and cost-effective bifunctional electrocatalysts for oxygen reduction and evolution reactions (ORR/OER) is essential in the advancement of solar fuels, metal-air batteries and unitized regenerative fuel cells. This work demonstrates an effective approach of activating 2D carbon for highly efficient bifunctional oxygen reactions without N-doping, let alone a transition metal-nitrogen (TM-N x ) moiety, the usual component needed for high oxygen electrocatalytic activities. A solvothermally synthesized ceria (CeO 2 )-hydroxylated graphene hybrid catalyst shows excellent bifunctional ORR/OER activities both in alkaline and acidic solutions. Density functional theory calculations reveal that the activation of graphene occurs via top-most oxygens on ceria surface, but only when low coverage of hydroxyl groups is present on graphene. Furthermore, catalytically active forms of graphene share similar hydroxylated structural motifs. Finally, a simple approach of dramatically enhancing durability even in acidic media is demonstrated.

Recent Advances of CeO2‐Based Electrocatalysts for Oxygen and Hydrogen Evolution as well as Nitrogen Reduction

“…[26] According to the current reports, ceria based hybrid materials have been flourishingly investigated in electrocatalysis, such as OER, HER, NRR, oxygen reduction reaction (ORR), methanol electrooxidation reaction (MOR) and etc. [27][28][29][30] And only two reviews have been presented about this interesting topic of CeO 2 -based materials for many kinds of electrocatalysis. [31,32] The research fruits and reviews signify that CeO 2 -based materials have the significant potential as multifunctional electrocatalysts.…”

“…In addition, CeO 2 has excellent mechanical stability and corrosion resistance under alkaline conditions, benefitting for the improvement of the structural robustness and durability during electrocatalysis [26] . According to the current reports, ceria based hybrid materials have been flourishingly investigated in electrocatalysis, such as OER, HER, NRR, oxygen reduction reaction (ORR), methanol electrooxidation reaction (MOR) and etc [27–30] . And only two reviews have been presented about this interesting topic of CeO 2 ‐based materials for many kinds of electrocatalysis [31,32] .…”

A highly durable graphene monolayer electrode under long-term hydrogen evolution cycling

“…It is worth mentioning that pristine graphene has also been found to be suitable for application as a potassium ion battery anode. 26 Starting out with such electrodes, through appropriate defect engineering 27 or chemical modification, we can reliably fabricate novel electrodes for the HER as well as for other electrocatalytic applications.…”