Rapid Surface Reconstruction of Amorphous Co(OH)₂/WO_x with Rich Oxygen Vacancies to Promote Oxygen Evolution

Abstract

Herein, a transition metal dissolution‐oxygen vacancy strategy, based on dissolution of highly oxidized transition metal species in alkaline electrolyte, was suggested to construct a high‐performance amorphous Co(OH)2/WOx (a‐CoW) catalyst for the oxygen evolution reaction (OER). The surface reconstruction of a‐CoW and its evolution were described by regulating oxygen vacancies. With continuous dissolution of W species, oxygen vacancies on the surface were generated rapidly, the surface reconstruction was promoted, and the OER performance was improved significantly. During the surface reconstruction, W species also played a role in electronic modulation for Co. Due to its rapid surface reconstruction, a‐CoW exhibited excellent OER performance in alkaline electrolyte with an overpotential of 208 mV at 10 mA cm−2 and had long‐term stability for at least 120 h. This work shows that the transition metal dissolution‐oxygen vacancy strategy is effective for preparation of high‐performance catalysts.

Defect Enriched Tungsten Oxide Phosphate with Strategic Sulfur Doping for Effective Seawater Oxidation

“…Having such alterations, it can be anticipated that the activation of electrocatalyst over the initial period, accompanied by the introduction of defects involving valence state changes for tungsten and the creation of a large number of oxygen vacancies lead to further boosting of OER performance, as also observed by comparing LSV plots before and after the chronoamperometry test. 61,62 Furthermore, to cater more evidence in support of these observations, the used electrodes after 24 and 48 h of chronoamperometry study were also well-examined with the help of Raman analysis, shown in Figure 5e, as a sensitive technique to investigate surface modifications that occurred during the stability test. Before the stability test in WPS-10, a broad signal in the range of 720−850 cm −1 can be attributed to W 6+ −O bonds, which disappear after 24 and 48 h, in line with the XPS results.…”

“…Precisely, an enhancement of oxygen vacancy from 30% before the stability test to 36% after CA test has been evaluated and for obvious reasons considerable increase in peak for adsorbed water can also be seen. Having such alterations, it can be anticipated that the activation of electrocatalyst over the initial period, accompanied by the introduction of defects involving valence state changes for tungsten and the creation of a large number of oxygen vacancies lead to further boosting of OER performance, as also observed by comparing LSV plots before and after the chronoamperometry test. , …”

W exsolution promotes the in situ reconstruction of a NiW electrode with rich active sites for the electrocatalytic oxidation of 5-hydroxymethylfurfural (HMF)

“…The acidic W oxides are widely recognized of their high tendency to dissolve in the strong alkaline solution. 24,26,28 In the as-prepared NiW/CP, WO x was thus supposed to easily detach and dissolve in the 1 mol L −1 (M) KOH electrolyte during the electrochemical scan. It is a common phenomenon that the current density initially decreases, and then becomes stable with increasing cyclic voltammetry (CV) cycles due to the stabilization of the ion concentration polarization near the surface of the electrode.…”

“…It was supposed to It has been reported that the selective exsolution of metal from the initial compound is able to produce vacancies and accelerate the self-reconstruction during the electrochemical oxidation reaction. [24][25][26][27][28] Herein, as the WO x was incorporated into and interacted with the lattice of the Ni species, it was hypothesized that the selective etching of the W species could create cation vacancies in the lattice of the Ni species. It might further promote the charge and/or ion transfer, and thus the self-reconstruction of the intermediate NiIJOH) 2 to form the high-valence NiOOH.…”

“…Especially, the creation of surface defects has been investigated to play a significant role on the in situ transformation of active sites. [24][25][26][27][28] On the other hand, WO x is well-known by its great capability of incorporation with Ni and modulation of its electronic structure. 29 Moreover, the exsolution of W from the incorporated structure is demonstrated to induce surface defects.…”