Highly Efficient Bifunctional Catalyst of NiCo₂ O₄ @NiO@Ni Core/Shell Nanocone Array for Stable Overall Water Splitting

Abstract

Electrochemical splitting of water is an efficient way to produce clean energy for energy storage and conversion devices. Herein, 3D hierarchical NiCo2O4@NiO@Ni core/shell nanocone arrays (NAs) are reported on Ni foam for stable overall water splitting with high efficiency. The architecture and composition of the 3D catalysts are particularly tuned. The outstanding structural and component features of the as‐prepared 3D catalysts are characterized by the vertically grown NiCo2O4 nanocone/NiO nanosheet core/shell structure and Ni decorated 3D‐conductive networks, which largely prompt the catalytic performance. The hybrid catalyst with core/shell nanocone array structures exhibits superior bifuncational activities for oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) with an overpotential of 240 and 120 mV at a current density of 10 mA cm−2, respectively. The Tafel slope of the optimal 3D electrode is about 43 and 58 mV dec−1 in an alkaline electrolyte for OER and HER, respectively. An alkaline electrolyzer constructed by two symmetric NiCo2O4@NiO@Ni electrodes delivers splendid activity toward overall water splitting with a current of 10 mA cm−2 at only ≈1.60 V and almost no deactivation after 10 h. This work provides a promising strategy to design ternary core/shell electrodes as high performance Janus catalysts for overall water splitting.

An Electrically Rechargeable Zinc/Air Cell with an Aqueous Choline Acetate Electrolyte

“…The Tafel slopes are listed in Table 2 where the first value is assigned to 1 to 10 and second one from 10 to 100 mA cm − 2 current density regions, respectively. These results are in good agreement with Wang et al [ 39 ] work in which binder-free bifunctional NiCo 2 O 4 @NiO and NiFe/NiCo 2 O 4 /NF were tested in 1.0 M KOH electrolyte [ 40 ]. Most relevant data related to the activity of different catalysts for ORR/OER such as mass activity (MA), Tafel slope, and ΔE are summarized in Table 2 .…”

Improved Electrocatalytic Performance in Overall Water Splitting with Rational Design of Hierarchical Co3O4@NiFe Layered Double Hydroxide Core‐Shell Nanostructure

“…What's more, the Co 3 O 4 @NiFe‐LDH/NF represents a small Tafel slope of 107.5 mV dec −1 (Figure S9). The HER performance of the Co 3 O 4 @NiFe‐LDH/NF is also superior or comparable to other reported values (Table S2) ,–,…”

Sea coral-like NiCo2O4@(Ni, Co)OOH heterojunctions for enhancing overall water-splitting

“…Figure 3b presents the OER polarization curves with a current density of 10 mAcm −2 , and the overpotential values follows the order from low to high with a sequence of: RuO 2 (200 mV) <NiCo 2 O 4 @(Ni, Co)OOH(220 mV) <NiCo 2 O 4 (240 mV), whereas the previously reported NiCo 2 O 4 @NiO@Ni with a larger OER overpotential (280 mV). 45 The NiCo 2 O 4 @(Ni, Co)OOH heterojunction exhibits a better electrocatalytic activity than the data of the NiCo 2 O 4 . Table S1 shows the comparison of HER and OER activity for NiCo 2 O 4 @(Ni, Co)OOH heterojunction with other recently published highly active electrocatalysts in alkaline electrolyte (1 M KOH).…”