Single‐Crystalline Ultrathin Co₃O₄ Nanosheets with Massive Vacancy Defects for Enhanced Electrocatalysis

Abstract

The role of vacancy defects is demonstrated to be positive in various energy‐related processes. However, introducing vacancy defects into single‐crystalline nanostructures with given facets and studying their defect effect on electrocatalytic properties remains a great challenge. Here this study deliberately introduces oxygen defects into single‐crystalline ultrathin Co3O4 nanosheets with O‐terminated {111} facets by mild solvothermal reduction using ethylene glycol under alkaline condition. As‐prepared defect‐rich Co3O4 nanosheets show a low overpotential of 220 mV with a small Tafel slope of 49.1 mV dec−1 for the oxygen evolution reaction (OER), which is among the best Co‐based OER catalysts to date and even more active than the state‐of‐the‐art IrO2 catalyst. Such vacancy defects are formed by balancing with reducing environments under solvothermal conditions, but are surprisingly stable even after 1000 cycles of scanning under OER working conditions. Density functional theory plus U calculation attributes the enhanced performance to the oxygen vacancies and consequently exposed second‐layered Co metal sites, which leads to the lowered OER activation energy of 2.26 eV and improved electrical conductivity. This mild solvothermal reduction concept opens a new door for the understanding and future designing of advanced defect‐based electrocatalysts.

Heterojunction and Oxygen Vacancy Modification of ZnO Nanorod Array Photoanode for Enhanced Photoelectrochemical Water Splitting

“…[25] X-ray photoelectron spectroscopy (XPS) was employed to determine the chemical compositiona tt he surface. [26] In addition, the peak corresponding to (Zn-bound) lattice oxygen in O v -CoO x /ZnO is weaker compared to CoO x /ZnO and pristine ZnO (Figure 3) ,s uggesting that solvothermalt reatment also leads to creationo fo xygen vacancies in ZnO NRs. The in-depthO 1s XPS spectraf or all samples are shown in Figure 3a-c.…”

Structural Engineering of Low‐Dimensional Metal–Organic Frameworks: Synthesis, Properties, and Applications

“…[25][26][27][28][29] Low-dimensional (LD) nanomaterials are of particular interest due to their anisotropic-tunable properties, which greatly influence their performances. [41][42][43][44][45][46][47] More recently, LD MOFs have attracted intensive interest and been investigated in various applications. [38][39][40] As another typical LD materials, 2D nanomaterials, such as 2D nanosheets of layered double hydroxides (LDHs), transition metal dichalcogenides (TMDs), hexagonal boron nitride, and MXenes, have attracted widespread attention since the discovery of graphene.…”

A general ligand-assisted self-assembly approach to crystalline mesoporous metal oxides

“…3g, the peaks at~780.3 (Fig. 3h) can be deconvoluted into three distinct peaks: oxygen ions in the crystal lattice (at 530.1 eV), oxygen vacancies (at 532.2 eV), and absorbed oxygen species (at 531.2 eV) 23 . The thermogravimetric analysis trace ( Figure S12) obtained after evaporation at 120°C shows two thermal events: a large weight loss at 180°C and a smaller weight loss at 350°C, which correspond to conversion from CoCO 3 to Co 3 O 4 and the combustion of residual carbon, respectively.…”