A Bifunctional Hybrid Electrocatalyst for Oxygen Reduction and Evolution: Cobalt Oxide Nanoparticles Strongly Coupled to B,N‐Decorated Graphene

Abstract

The electrocatalyzed oxygen reduction and evolution reactions (ORR and OER, respectively) are the core components of many energy conversion systems, including water splitting, fuel cells, and metal-air batteries. Rational design of highly efficient non-noble materials as bifunctional ORR/OER electrocatalysts is of great importance for large-scale practical applications. A new strongly coupled hybrid material is presented, which comprises CoO nanoparticles rich in oxygen vacancies grown on B,N-decorated graphene (CoO NPs/BNG) and operates as an efficient bifunctional OER/ORR electrocatalyst. Advanced spectroscopic techniques were used to confirm formation of abundant oxygen vacancies and strong Co-N-C bridging bonds within the CoO NPs/BNG hybrid. Surprisingly, the CoO NPs/BNG hybrid electrocatalyst is highly efficient for the OER with a low overpotential and Tafel slope, and is active in the ORR with a positive half-wave potential and high limiting current density in alkaline medium.

Engineering Morphologies of Cobalt Pyrophosphates Nanostructures toward Greatly Enhanced Electrocatalytic Performance of Oxygen Evolution Reaction

“…The Ir/C electrode reveals a Tafel slope of 70.2 mV dec −1 , comparable to the previously reported value . Interestingly, CoPPi nanowires electrode exhibits a Tafel slope of 54.1 mV dec −1 , substantially lower than that of Ir/C, and also the CoPPi nanobelts (57.9 mV dec −1 ), nanoleaves (81.6 mV dec −1 ), and nanorhombuses (118.5 mV dec −1 ), suggesting the favorable OER kinetics of CoPPi nanowires . Note that this value is lower than the reported CL‐Co 2 P 2 O 7 @C (70 mV dec −1 ) and the other CoPi based catalysts, for example, mesoporous CoPi (58.7 mV dec −1 ), Co 3 (PO 4 ) 2 @N‐C (62 mV dec −1 ), and CC/NPC/CP (80 mV dec −1 ) .…”

Probing the Active Sites of Carbon‐Encapsulated Cobalt Nanoparticles for Oxygen Reduction

“…The ORR is tested in an oxygen‐saturated 0.1 m KOH electrolyte using a rotating disk electrode. We can see from Figure a that with the commonly used catalyst loading of 0.32 mg cm −2 , the ORR activity of the Co@C is similar to that of the reported Co‐based catalysts . Considering the efficiency of the electrochemical activation, we used a reduced catalyst loading of 0.04 mg cm −2 to remove the Co cores as many as possible.…”

“…Subsequently, enormous researches have been devoted to exploiting various Co‐ or Fe‐based materials for catalyzing the ORR. Typical examples include cobalt/iron oxide coupled with graphene, carbon nanotubes coupled with cobalt/iron nanoparticles, and carbon encapsulated cobalt/iron nanoparticles …”

Tungsten‐Doped CoP Nanoneedle Arrays Grown on Carbon Cloth as Efficient Bifunctional Electrocatalysts for Overall Water Splitting

“…The scanning electron microscopy (SEM) image and the corresponding XRD of CoÀ OH/CC are depicted in Figure S3, suggesting the CoÀ OH/CC and WÀ CoÀ OH/CC have the similar morphology and phase structure. [20] The two main peaks at 781.7 and 797.6 eV are attributed to Co 2p 3/2 and Co 2p 1/2 of WÀ CoÀ OH/CC, respectively [21] and the binding energies of Co 2p 3/2 and Co 2p 1/2 peaks of WÀ CoÀ OH/CC blueshifted compared to CoÀ OH/CC, suggesting that the electronic structure of Co is modified by W doping. Figure S4a and 4b display the fine XPS spectra of Co 2p and W 4 f of WÀ CoÀ OH/CC and CoÀ OH/CC.…”