N-doped graphene film-confined nickel nanoparticles as a highly efficient three-dimensional oxygen evolution electrocatalyst

Abstract

A three-dimensional (3D) catalyst was fabricated by using N-doped graphene films as scaffolds and nickel nanoparticles as building blocks via a heterogeneous reaction process. This unique structure enables high catalyst loadings and optimal electrode contact, leading to a surprisingly high catalytic activity towards OER, which almost approaches that of the state-of-the-art precious OER electrocatalysts (IrO 2 ). Moreover, the catalytic process features favourable electrode kinetics and strong durability during long-term cycling. The dual-active-site mechanism was proposed for this 3D catalyst, i.e., Ni/NiOOH and Ni-N(O)-C are both active sites. The enhanced performance is attributed to synergistic effects of N-doped graphene and Ni, which enhance the activities of both components for OER. Broader contextOxygen evolution reaction (OER) is coupled with a number of key renewable energy systems like solar cells, metal-air batteries and water splitting. OER proceeds through a multistep electron transfer process, and is kinetically sluggish. Recently, three-dimensional (3D) macroscopic catalysts have attracted considerable interest due to their multiple advantages such as high catalyst loadings and excellent electrode contact. However, challenges with current 3D catalysts are their low efficiency and inferior durability. This work presents a new class of 3D electrodes for catalyzing OER. It is shown that the incorporation of nickel nanoparticles into N-doped graphene lms results in 3D catalysts that exhibit remarkable catalytic efficiency as well as high stability.

An Advanced Nitrogen‐Doped Graphene/Cobalt‐Embedded Porous Carbon Polyhedron Hybrid for Efficient Catalysis of Oxygen Reduction and Water Splitting

“…[ 28 ] Such phenomenon is commonly observed in N-doped graphene materials because the insertion of nitrogen atoms can cause distortion of the sp2 carbon lattice of graphene. [ 29 ] Therefore, the results provide evidence for the incorporation of N atoms into the RGO.…”

“…The positive carbon atoms can facilitate adsorption of OH ions, promote the electron transfer between the catalyst surface and reaction intermediates, resulting in the OER. [ 29,52 ] Signifi cantly, the overpotential of the hybrid was comparable to those of other reported OER catalysts, including N-doped graphene/singlewalled carbon nanotube hybrid (1.63 V vs RHE), [ 53 ] N-doped graphite (1.61 V vs RHE), [ 11 ] crumpled graphene/CoO (1.65 V vs RHE), [ 51 ] Mn 3 O 4 /CoSe 2 hybrid (1.68 V vs RHE), [ 54 ] CaMn 4 O x (1.77 V vs RHE), [ 55 ] Mn x O y nanoparticles embedded nitrogendoped carbon (1.68 V vs RHE), [ 52b ] and rutile IrO 2 (1.68 vs RHE). [ 56 ] As for Pt/C, the overpotential acquired for the current density of 10 mA cm −2 would be much more positive, as deduced from the corresponding current trend.…”

Metal (Ni, Co)‐Metal Oxides/Graphene Nanocomposites as Multifunctional Electrocatalysts

“…[ 17 ] Furthermore, combining graphene with metal or metal oxide is an effective way to improve catalytic activities due to the high surface area and excellent electrical conductivity of graphene, [18][19][20] thereby increasing number of active sites and promoting the charge transfer in electrodes. [21][22][23] For example, Co 3 O 4 /graphene, [ 24 ] Ni/graphene fi lm, [ 25 ] and NiO/rGO [ 26 ] composite catalysts have been explored showing enhanced catalytic activity, relative to single metals or metal oxides. Based on previous studies on the nickel or cobalt electrocatalysts, in this work, we synthesized a new family catalyst including Co-CoO/N-rGO and Ni-NiO/N-rGO via a pyrolysis of graphene oxide-supported cobalt and nickel salts, respectively.…”

Nitrogen and Sulfur Codoped Graphite Foam as a Self‐Supported Metal‐Free Electrocatalytic Electrode for Water Oxidation

“…To overcome these problems, 3D structured electrodes with nickel foams or porous carbon hydrogel fi lms have been developed to immobilize catalysts. [ 21,[23][24][25][26] The high macroporosity of nickel foam can greatly increase the accessible specifi c surface areas of loaded catalysts, and facilitate the removal of gases. [ 23 ] However, the intrinsic instability of nickel decreased the long-term durability of these catalysts.…”