Focused Plasma- and Pure Water-Enabled, Electrode-Emerged Nanointerfaced NiCo Hydroxide–Oxide for Robust Overall Water Splitting

Abstract

Bimetallic, bifunctional electrocatalysts capable of driving both oxygen (OER) and hydrogen (HER) evolution half-reactions on both electrodes in commercial water electrolysis cells are among the most promising materials systems for clean hydrogen energy generation. However, insufficient hydrogen and oxygen production activity at industry-relevant current densities and long-term catalyst stability on the electrode surface prevent this approach from industrial translation. This work resolves these challenges by advancing the promising, yet far-fromsuccessful attempts to sprout bimetallic electrocatalytic nanostructures directly from electrode frames. For the first time, we utilize magneticfield-focused, atmospheric-pressure plasma jets in oxygen−argon gas mixtures to successfully induce the nanointerfaced bimetallic NiCo hydroxide and oxide catalyst phases. After a simple hydrothermal treatment in pure water, NiCo bimetallic hydroxide nanosheets are densely covered with strongly bonded bimetallic NiCo oxide nanoparticles which ensure high catalytic activity evidenced by the low overpotentials for both HER and OER for delivering a current density of 100 mA cm −2 (j 100 ) of only 306 and 484 mV, respectively. The electrode-emerged nanointerfaced NiCo hydroxide−oxide bimetallic system (NiCo 2 O 4 −NiCo(OH) x ) shows an ultrastable electrocatalytic performance under a high current density of j 200 , which only decays 5.8% and 6.3% for HER and OER processes within 100 h. The competitive H 2 and O 2 production rates are about 1.27 and 0.69 mmol h −1 cm −2 (near to 2:1, under j 10 conditions), meeting a nearly 100% Faradaic efficiency. Furthermore, the theory calculation indicates that the Ni and Co sites of NiCo 2 O 4 −NiCo(OH) x are the catalytic centers for the HER process. Our new plasma-enabled approach for the controlled production of bimetallic hydroxide−oxide active nanointerfaced systems is generic and is potentially suitable for diverse materials systems and applications well beyond electrocatalysis.

Plasma modified and tailored defective electrocatalysts for water electrolysis and hydrogen fuel cells

“…(F) Magnetic field‐enhanced, focused atmospheric‐pressure plasma jet system for synthesizing the electrode‐emerged nanointerfaced bimetallic hydroxide–oxide electrocatalysts. Reproduced with permission: Copyright 2021, American Chemical Society 92 . (G) Atmospheric‐pressure plasma jet (APPJ) system for the construction of nonstoichiometric ultrathin Ni x O y layers.…”

“…Zhuang et al have reported an Ar plasma approach to synthesize Ir/Cu oxide nano‐clusters evenly on defective graphene as pH‐universal water splitting electrocatalysts 114 . Chen et al have utilized magnetic‐field focused plasma jets of atmospheric‐pressure O 2 /Ar (Figure 7F) to produce nano‐interfaced NiCo LDH nanosheets anchored with NiCo oxide nanoparticles for robust overall water splitting 92 . The high‐density Ar ions increase the reactive sites by etching following nucleation and growth of LDH and exposure to the O 2 /Ar plasma provides the reactive precursors for subsequent formation of bimetallic oxide spherical particles.…”

“…Reproduced with permission: Copyright 2021, American Chemical Society. 92 (G) Atmospheric-pressure plasma jet (APPJ) system for the construction of nonstoichiometric ultrathin Ni x O y layers. Reproduced with permission: Copyright 2021, American Chemical Society.…”

“…114 Chen et al have utilized magnetic-field focused plasma jets of atmospheric-pressure O 2 /Ar (Figure 7F) to produce nano-interfaced Ni Co LDH nanosheets anchored with Ni Co oxide nanoparticles for robust overall water splitting. 92 The high-density Ar ions increase the reactive sites by etching following nucleation and growth of LDH and exposure to the O 2 /Ar plasma provides the reactive precursors for subsequent formation of bimetallic oxide spherical particles. This plasma-based method can synthesize bimetallic hydroxide-oxide nanointerfaced materials.…”

Heterostructured Palladium–Nickel Sulfide on Plasma-Activated Nickel Foil for Robust Hydrogen Evolution

“…Noted that the information about the instruments and detection methodology and parameters has been provided in our reported work. 24 Electrochemical Measurements. At room temperature, all electrochemical tests are performed by an electrochemical workstation (Model: CHI 660E, Shanghai Chenhua Instrument Co, Ltd) with an alkaline medium (1.0 M KOH), where the catalyst, Hg/HgO, and a carbon rod serve as the working, reference, and counter electrodes, respectively.…”