Probing the Crystal Plane Effect of Co₃O₄ for Enhanced Electrocatalytic Performance toward Efficient Overall Water Splitting

Abstract

Identifying effective methods to enhance the properties of catalysts is urgent to broaden the scanty technologies, so far. Herein, we synthesized four CoO crystals with different crystal planes and explored the crystal planes' effects on electrochemical water splitting through theoretical and experimental studies for the first time. The results illustrate that the correlation of catalytic activity is established as {111} > {112} > {110} > {001}. CoO crystals exposed with {111} facets show the highest OER (oxygen evolution reaction) and HER (hydrogen evolution reaction) activities. Upon fabrication in an alkaline electrolyzer, the bifunctional {111}∥{111} couple manifests the highest catalytic activity and satisfying durability for overall water splitting. Density functional theory (DFT) explains that the {111} facet possesses the biggest dangling bond density, highest surface energy, and smallest absolute value of ΔG, leading to the enhanced electrocatalytic performance. This work will broaden our vision to improve the activity of various electrocatalysts by selectively exposing the specific crystal planes.

Identifying the Intrinsic Relationship between the Restructured Oxide Layer and Oxygen Evolution Reaction Performance on the Cobalt Pnictide Catalyst

“…Co 3 O 4 , Co x N, and Co x P were synthesized using a hydrothermal method (see Section 4), as reported in the literature. [ 20–22 ] The crystalline structure of pristine samples was identified by X‐ray diffraction (XRD). As shown in Figure S1, Supporting Information, XRD pattern of the pristine Co 3 O 4 was in good agreement with the PDF card #43‐1003, while the diffraction peaks of the pristine Co x N and Co x P shifted toward lower and higher angles than the stoichiometric Co 2 N and CoP, respectively, indicating the presence of non‐stoichiometric composition.…”

Orienting Active Crystal Planes of New Class Lacunaris Fe2PO5 Polyhedrons for Robust Water Oxidation in Alkaline and Neutral Media

“…Therefore, the modulation of exposed crystal planes of 3D iron phosphate crystal is unable to achieve in spite of the important role of crystal planes in regulating electrocatalysis activity toward water oxidation. For examples, spinel Co 3 O 4 nanosheets, nanocubes, and nanopolyhedrons with different exposure crystal planes can be developed by controlling the synthetic procedure and condition . Particularly, Fe 2 O 3 with predominantly {110} facets and BiVO 4 polyhedrons with specific high‐index planes also exhibit excellent water oxidation activity .…”

Porous Cobalt–Nickel Hydroxide Nanosheets with Active Cobalt Ions for Overall Water Splitting

“…Regarding HER in alkaline solution, hydrogen atoms evolve from the initial H 2 O state to intermediate H* state and ultimate H 2 state . An optimal HER catalyst should possess the appropriate ability to absorb H* species and to release H 2 .…”