Boosting the Stability of Oxygen Vacancies in α‐Co(OH)₂ Nanosheets with Coordination Polyhedrons as Rivets for High‐Performance Alkaline Hydrogen Evolution Electrocatalyst

Abstract

The strong alkaline electrolytes are utilized in various key electrochemical applications and the severe corrosion by hydroxyl ions endows the development of high‐performance electrode materials with a great challenge. Here, an effective strategy is demonstrated to stabilize α‐Co(OH)2 under harsh alkaline electrochemical condition by coordination polyhedron pinning (MoO42−, WO42−) on the surface for hydrogen evolution reaction (HER). The addition of MoO42− in 1 m KOH can inhibit the attack of hydroxyl ions on oxygen vacancies in α‐Co(OH)2, and simultaneously modulate the electronic structure of active sites for HER. The theoretical calculations and experimental results reveal that MoO42− can be riveted on the surface of α‐Co(OH)2 to greatly stabilize oxygen vacancies and inhibit the formation of soluble ions of Co(OH)3−. The resultant active sites exhibit reduced maximum energy barriers for the optimized alkaline HER. Additionally, MoO42− near the interface between α‐Co(OH)2 and electrolyte can alleviate the accumulation of hydroxyl ions on α‐Co(OH)2 due to the electrostatic repulsion, improving the stability toward HER. This work offers insight into the role of coordination polyhedron ions in regulating and enhancing the stability of α‐Co(OH)2 for various potential electrochemical applications in alkaline electrolyte.

Unveiling coordination transformation for dynamically enhanced hydrogen evolution catalysis

“…It is believed that the electronic structure of the Co atoms in the shortened Co–O bond may have the optimal binding capability with hydrogen intermediates and thus demonstrate enhanced HER activity and stability. 11,23,37 Furthermore, the CN in the Co–O and Co–O–Co shells in CoB i /MXene rises significantly from 5.4 to 7.8 and from 4.0 to 5.6, respectively, at potentials exceeding OCV. Compared with the saturated six-coordination, this implies that the increased CN in cobalt hydroxide during the electrocatalysis can result from the coordination of in situ generated oxyanions.…”

“…Considering that the addition of BO 3 3À does not affect the pH of the electrolyte, we speculate that the enhanced catalytic activity can be attributed to the surface-coordinated borates. 34,35,37 Taken together, the displacement of borate anions induced by MXene leads to a dynamic structural transformation to form the Co(OH) 2 active phase, further enhancing the HER activity.…”

“…Therefore, it is imperative to systematically examine the anionic behavior of the catalysts during the HER process to address the relevant research gaps. 37,38 Moreover, the activation process of many catalysts under their operating conditions directly exhibits catalytic activity decay due to the oxidation and anion leaching of the pre-catalyst surface, which hinders the understanding of the structure-activity relationship. 31 Thus, developing highly active and ultrastable cobalt-based electrocatalysts and identifying the actual active species during the HER is beneficial for the rational design of efficient electrocatalysts.…”

Surface and near-surface engineering design of transition metal catalysts for promoting water splitting

“…Intriguingly, Jiang et al discovered that WO 4 2À with a similar structure also exhibited a positive effect on HER catalysis. 137 The addition of WO 4 2À to KOH solution inhibits the attack of OH À on oxygen vacancies of a-Co(OH) 2 and adjusts the electronic structure of active sites, eventually achieving high OER activity and stability (Fig. 12d).…”

Universal phase transformation of Ni–Se electrocatalysts induced by an electrochemical activation strategy for a significantly enhanced alkaline hydrogen evolution reaction

“…[1][2][3][4] The major driving force is the strong interaction between electrocatalysts and ions in the electrolyte under an applied electric field, causing the leaching of elements with the formation of vacancies and defects and the reconstruction of catalytic sites, and consequently reducing the stability of the crystal structure. [5][6][7] For instance, the FeSe precatalyst will be converted into amorphous Sedoping FeOOH accompanied by Se leaching as the real catalytic active component that possesses higher catalytic activity for the oxygen evolution reaction (OER). 8 Therefore, understanding the structural and component evolution of the targeting electro-catalysts is an effective way to identify the real catalytic active sites for rationally designing highly efficient catalysts.…”