Progress in Nonmetal‐Doped Graphene Electrocatalysts for the Oxygen Reduction Reaction

Abstract

Owing to energy shortages and environmental pollution, green energy sources such as polymer electrolyte fuel cells and metal–air batteries play a more and more important role, whereby the oxygen reduction reaction (ORR) is the rate‐determining step. Development of high‐efficiency and stable catalysts to facilitate the ORR is of importance. Graphene is a new type of material with two‐dimensional structure and high surface area, which has wide‐ranging applications in many fields. However, graphene with zero band gap shows low electrocatalytic activity toward the ORR. Introduction of nonmetal atoms can change the electronic arrangement, generate active sites, and further improve the catalytic activity of graphene. Some nonmetal‐doping strategies (e.g., N, S, and P doping) can promote ORR activity. Herein, the recent development of nonmetal‐doped graphene catalysts for ORR is reviewed. Some common synthetic methods for nonmetal‐doped graphene materials are summarized, and the active sites and possible reaction mechanisms for ORR on various nonmetal‐doped graphene catalysts are discussed.

Ultrasmall Co@Co(OH)2 Nanoclusters Embedded in N‐Enriched Mesoporous Carbon Networks as Efficient Electrocatalysts for Water Oxidation

“…Moreover, their stabilization on the porous carbon network with abundant doped nitrogen atoms consequently generates a hybrid heterostructure and thus nanointerfaces and surface active sites. Such nanoscale interfacial collaboration could facilitate the easy adsorption/desorption of reaction intermediates (O − , OH − , OOH − ) to possibly buffer the four‐electron process needed for OER catalysis . More promisingly, the slight increase in C dl (from 12 to 13.8 mF cm −2 ) and consequently ECSA after catalysis (Figure S13 in the Supporting Information) and high turnover frequency (TOF=350 s −1 at 1.56 V, Figure S10 in the Supporting Information) highlight the regeneratable behavior of the active sites (hydroxide/oxyhydroxide), showing that OER can be maintained in a durable manner .…”

“…Such nanoscale interfacialc ollaboration could facilitate the easy adsorption/desorptionofr eaction intermediates (O À ,OH À ,O OH À )t opossibly buffer the four-electron process neededf or OER catalysis. [38] More promisingly,t he slight increasei nC dl (from 12 to 13.8 mF cm À2 )a nd consequently ECSA after catalysis (Figure S13 in the Supporting Information) and high turnover frequency( TOF = 350 s À1 at 1.56 V, Figure S10i nt he Supporting Information) highlight the regeneratableb ehavior of the active sites (hydroxide/oxyhydroxide), showingthat OER can be maintained in ad urable manner. [27] This behavior is also evident from the chronoamperometry at 10 mA cm À2 ,i nw hich ad ecrease in the required potential (dependentp arameter) in the initial hours of the stability test indicates the continuous activation of embedded/surface active sites ( Figure S8 di nt he Supporting Information).…”

3D Carbon Materials for Efficient Oxygen and Hydrogen Electrocatalysis

“…In 2009, Dai's group demonstrated for the first time a superior activity of metal‐free ORR catalysis in alkaline media compared to Pt/C, using vertically aligned nitrogen‐doped CNT arrays and highlighting the role of nitrogen in greatly enhancing the activity over pure CNTs . Since then, much progress has been made in the use of heteroatom doping to enhance the activity of 1D (CNTs) and 2D (graphene) carbons toward the ORR, summarized in the recent review by Shao et al As well as tuning the electronic structure of the carbon matrix via heteroatom doping, modifying the structure of the nanomaterials is important to enhance surface area, mass transport of reactants, and electrical conductivity. Additionally, 1D or 2D catalysts can be difficult to process into working electrodes and may suffer from a lack of mechanical robustness or re‐staking of nanomaterials.…”

Defective NiFe2O4 Nanoparticles for Efficient Urea Electro‐oxidation

“…In order to prepare high‐performance urea electro‐oxidation catalysts, many methods have been developed, including preparing 2D nanosheets, synthesizing heterostructures, and growing on conductive substrates . In recent years, defect engineering strategy was widely adopted for optimizing the catalytic property of various catalysts in many areas, including photocatalytic hydrogen evolution and electrocatalytic hydrogen evolution, oxygen evolution as well as oxygen reduction . Actually, significantly enhanced catalytic performances were found by researchers mainly owing to the increased numbers of active sites .…”

“…[4,24] In recent years, defect engineering strategy was widelya dopted for optimizing the catalytic property of various catalysts in manya reas, including photocatalytic hydrogen evolution [25][26][27] and electrocatalytic hydrogen evolution, [28][29][30][31][32][33][34][35] oxygen evolution [36][37][38][39] as wella so xygen reduction. [40][41][42] Actually,s ignificantly enhanced catalytic performances were found by researchers mainly owing to the increased numberso f active sites. [43,44] Therefore, defecte ngineering has been regarded asa ne ffective strategy to improve the properties of catalysts.…”