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

Guangliang Chen; Dongliang Chen; Jun Huang; Cheng Zhang; Wei Chen; Tongtong Li; Bangdou Huang; Tao Shao; Jian Li; Kostya Ken Ostrikov

doi:10.1021/acsami.1c13480

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

ACS Appl Mater Interfaces. 2021 Sep 29;13(38):45566-45577. doi: 10.1021/acsami.1c13480. Epub 2021 Sep 14.

Authors

Guangliang Chen^{1

2}, Dongliang Chen², Jun Huang³, Cheng Zhang⁴, Wei Chen³, Tongtong Li², Bangdou Huang⁴, Tao Shao⁴, Jian Li¹, Kostya Ken Ostrikov

Affiliations

¹ State Key Laboratory of Power Transmission Equipment & System Security and New Technology, Chongqing University, Chongqing 400044, P. R. China.
² School of Materials Science and Engineering, Zhejiang Sci-Tech University, Hangzhou 310018, P. R. China.
³ School of Physics and Electronic Information, Gannan Normal University, Ganzhou, Jiangxi 341000, P. R. China.
⁴ Institute of Electrical Engineering, Chinese Academy of Sciences, Beijing 100190, P. R. China.

PMID: 34519473
DOI: 10.1021/acsami.1c13480

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-from-successful attempts to sprout bimetallic electrocatalytic nanostructures directly from electrode frames. For the first time, we utilize magnetic-field-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 (j₁₀₀) of only 306 and 484 mV, respectively. The electrode-emerged nanointerfaced NiCo hydroxide-oxide bimetallic system (NiCo₂O₄-NiCo(OH)_x) shows an ultrastable electrocatalytic performance under a high current density of j₂₀₀, which only decays 5.8% and 6.3% for HER and OER processes within 100 h. The competitive H₂ and O₂ production rates are about 1.27 and 0.69 mmol h^-1 cm^-2 (near to 2:1, under j₁₀ conditions), meeting a nearly 100% Faradaic efficiency. Furthermore, the theory calculation indicates that the Ni and Co sites of NiCo₂O₄-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.

Keywords: bifunctional electrocatalyst; magnetically focused atmospheric-pressure plasma jet; overall water splitting; spatially confined interface activation; transition-bimetallic hydroxide−oxides.