Seamlessly Conductive 3D Nanoarchitecture of Core–Shell Ni‐Co Nanowire Network for Highly Efficient Oxygen Evolution

Abstract

Electrochemical splitting of water is an attractive way to produce hydrogen fuel as a clean and renewable energy source. However, a major challenge is to accelerate the sluggish kinetics of the anodic half‐cell reaction where oxygen evolution reaction (OER) takes place. Here, a seamlessly conductive 3D architecture is reported with a carbon‐shelled Ni‐Co nanowire network as a highly efficient OER electrocatalyst. Highly porous and granular Ni‐Co nanowires are first grown on a carbon fiber woven fabric utilizing a cost‐effective hydrothermal method and then conductive carbon shell is coated on the Ni‐Co nanowires via glucose carbonization and annealing processes. The conductive carbon layer surrounding the nanowires is introduced to provide a continuous pathway for facile electron transport throughout the whole of the integrated 3D catalyst. This 3D hierarchical structure provides several synergistic effects and beneficial functions including a large number of active sites, easy accessibility of water, fast electron transport, rapid release of oxygen gas, enhanced electrochemical durability, and stronger structural integrity, resulting in a remarkable OER activity that delivers an overpotential of 302 mV with a Tafel slope of 43.6 mV dec−1 at a current density of 10 mA cm−2 in an alkaline medium electrolyte (1 m KOH).

A review of transition metal‐based bifunctional oxygen electrocatalysts

“…As for the study of OER in Co 3 O 4 electrocatalysts, water oxidation activity can be generally ascribed to the presence of Co 4+ , which originates from the CoO 2 /CoOOH redox couple right before the onset of the OER. Based on this, Co in NiCo oxide‐based electrocatalysts such as NiCo 2 O 4 @MnO x , NiO/NiCo 2 O 4 , NiCo@NiCoO x , NiCo 2 O 4 , Ni‐Co nanowire, Ni x Co 3− x O 4− y , hollow mesoporous NiCo 2 O 4 , and Ni/NiO/NiCo 2 O 4 can weaken OH bonds in absorbed OH through affinity to O atoms. In addition, the Ni counterpart of these catalysts can help to dissociate protic H through affinity to H atoms, leading to the synergistic enhancement of OH bond breakage.…”

Solar‐to‐Hydrogen Energy Conversion Based on Water Splitting

“…Thereafter, there are two typical pathways to generate an O 2 molecule based on the metal-oxo species. [7,148,157] Adv. Less likely, two adjacent metal-oxo species may interact together to form the OO bond provided with the proper distance between the two oxygen atoms.…”

“…To find an alternative process for the conversion of solar energy, the hydrogen fuel cell coupled with hydrogen production from solar-driven water www.advancedsciencenews.com splitting is an ideal strategy. In an acidic electrolyte, partial and full NiCoP/rGO j) CP 1 m KOH 270 [190] CoO x @NC NF k) 1 m KOH 260 [191] CoP NS/carbon GC 1 m KOH 277 [192] Co 3 O 4 NTs l) NF 1 m KOH 353 [193] Co NP GC 0.1 m KOH 390 [168] Co-Pi NA n) Ti mesh 0.1 m PBS 450 [194] CoP-NRA o) NF 1 m KOH 290 [195] CoFeNiO x NF 1 m KOH 240 [196] rGO@CoNiO x GC 0.1 m KOH 320 [197] Mn-Co oxyphosphide particles GC 1 m KOH 320 [198] Titanium carbide-carbon nitride Free-standing film 0.1 m KOH 420 [199] FeNC sheets/NiO GC 0.1 m KOH 390 [154] Ni-Co NWs p) Carbon fiber 1 m KOH 302 [157] Ultrathin Figure 4. Hydrogen is produced by the solar-driven processes described in the above section of this review.…”

Active Site Identification and Evaluation Criteria of In Situ Grown CoTe and NiTe Nanoarrays for Hydrogen Evolution and Oxygen Evolution Reactions

“…As well known, the adhesives (such as Nafion) on the electrode will hinder gas bubble generation in the water splitting process and therefore lead to the degradation of catalyst performance. Therefore, constructing 3D architecture by vertically growing nanotube or nanorod on conductive substrates may overcome the above issue efficiently, because the absence of adhesives can increase the electrochemically active surface area, and promote electrolyte penetration and electron transportation …”