Synthesis And Performance Of Carbon Coupled Cobalt-based Layered Double Hydroxides As Electrocatalysts For Oxygen Evolution Reaction

Hydrogen is perceived as an ideal and clean fuel,which serves as one of available solutions to address the current energy crisis.Electrocatalytic water splitting has become the most feasible way to produce hydrogen due to a number of advantages including simple process,abundant sources and extremely pure hydrogen.Water splitting involves two half reactions: hydrogen evolution reaction and oxygen evolution reaction(OER),whose kinetics are both sluggish,leading to high energy consumptions and lowering the overall efficiency of water splitting.Especially,the kinetics of OER are more complex,resulting in higher overpotentials than the other one.Hence,cost-efficient and stable electrocatalysts are highly needed to reduce overpotential losses for OER,thus to address the problem mentioned above.Layered double hydroxides(LDH)feature superior activities for OER since their facile tunability of the composition and morphology,and easily being coupled.Nevertheless,the OER performance of LDH is seriously limited by the low electrical conductivity.Such an issue can be conquered efficiently by the combination of carbon materials and LDH into nanohybrids to fabricate highly active OER electrocatalysts.In the case of nanohybrids,LDH are responsible for providing the electrocatalytic active sites,while carbon materials can accelerate the charge transfer process.Herein,we present two electrode materials composed of carbon coupled cobalt-based LDH and investigate their corresponding OER performance.The detail is as follows:A co-precipitation method was used to configure nanohybrids composed of carbon nanotubes(CNTs)coupled CoMn-LDH.Ultrathin CoMn-LDH nanoplates feature highly exposed active sites,a high interfacial contact area with the electrolyte and short ion-diffusion paths.Whereas,the CNTs with well-interconnected conductive frameworks help to enhance the conductivity of CoMn-LDH nanoplates,facilitating the transportation of electrons and further increasing the exposed active site.In 0.1 M KOH,the as-made CoMn-LDH/CNT nanohybrids achieve excellent OER performance with a small overpotential(355 mV at 10 mA cm-2),and prominent electrochemical durability.A carbon fiber paper(CFP)-assisted strategy was presented to mediate in situ growth of NiCo-LDH nanoarrays.CFP as the robust substrate and current collector is capable of not only promoting fast electron transport,but also modulating NiCo-LDH nanoplates assembly.The interconnected and open frameworks derived from the vertically oriented NiCo-LDH nanoplates on the surface of CFP not only expose more open coordination sites located along the edges,but also achieve outstanding abilities of mass transport and oxygen diffusion.In 1 M KOH,the binder-free electrocatalyst delivers an overpotential of 307 mV at 10 mA cm-2 and keeps a nearly constant potential during 20-h testing at a high current density of 100 mA cm-2,even no obvious changes for the morphology.