Promoting Formation of Oxygen Vacancies in Two-Dimensional Cobalt-Doped Ceria Nanosheets for Efficient Hydrogen Evolution

Abstract

As an alternative for depleting fossil fuel energy, hydrogen economy desires low-cost and efficient hydrogen production from water splitting. In order to explore a cheap, abundant, active, and durable catalyst for the electrocatalytic hydrogen evolution reaction (HER), two-dimensional (2D) ceria nanosheets are produced through a thermal decomposition exfoliation method from CeCO 3 OH with a layer-stacked structure. The additional cobalt dopant promotes formation of oxygen vacancies in ceria nanosheets and, in turn, optimizes hydrogen binding/water dissociation and increases the active sites. As a result, the 2D Codoped CeO 2 nanosheets exhibit an excellent catalytic performance in alkaline HER such that the overpotential is as low as 132 and 215 mV to deliver a high current density of 100 and 500 mA cm −2 , respectively, outperforming Pt. Such 2D Co-doped CeO 2 nanosheets are also durable HER electrocatalysts, as the activity loss during an extended period of operation is nearly negligible.

Recent Progress of Vacancy Engineering for Electrochemical Energy Conversion Related Applications

“…Then oxygen vacancies have been explored to improve electrocatalytic performance extensively by tuning electronic structure and regulating intrinsic physiochemical properties. [ 22c,24,26 ] For instance, Kang and co‐workers [ 27 ] synthesized 2D Co‐doped CeO 2 (Co‐doped CeO 2 ) via a facile solvothermal and subsequent calcination process ( Figure a). X‐ray photoelectron spectroscopy (XPS) measurement demonstrated the presence of oxygen vacancies in Co‐doped CeO 2 , and the cobalt doping promotes formation of oxygen vacancies.…”

Ce(OH)2Cl and lanthanide-substituted variants as precursors to redox-active CeO2materials

“…24 Isovalent substitution of Ce 3+ by other trivalent lanthanides to yield Ce 1−x Ln x CO 3 (OH) has proved possible, 25 and recently cobaltdoping of the precursor was found as a facile route to Codoped CeO 2 nanosheets with electrocatalytic properties. 26 The crystalline lanthanide chloride hydroxides, Ln(OH) 2 Cl, were reported in the 1960s for Ln = La, Pr, Nd, Sm and Gd, 27 and their crystal structures determined in these and subsequent works, 28 as well as further examples found for other lanthanides. 29 An exception is the case of Ce (OH) 2 Cl, which although was mentioned by Klevtsov et al in 1969, 27c was not structurally characterised until 2017 when Kim et al prepared the material using a hexamethylenetetramine solution route in the form of powders and as films.…”

Design and operando/in situ characterization of precious‐metal‐free electrocatalysts for alkaline water splitting

“…21,168 These effects facilitate the electron transfer and intermediate exchange rate, contributing to the distinctive OER/HER activity. The introduction of defects commonly involves "top-down" approaches, including plasma treatment, 43 thermal treatment, 69 and chemical reduction, 169 as well as "bottom-up" strategy, such as doping, 58 hydrothermal treatment, 11 and chemical vapor deposition. 170 Among them, doping is commonly adopted owing to the simple process and improved catalytic performance.…”

“…In this strategy, oxygen vacancies attracted great attention because of the low formation energy and significantly changed surface electronic properties. 11,58,169 Metal oxides/hydroxides with abundant oxygen vacancies displayed improved catalytic performance in comparison with untreated catalysts. For example, Co 3 O 4 nanosheets with abundant oxygen vacancies were prepared by mild hydrothermal reduction with the aid of ethylene glycol.…”

“…Successively, 2D Co-doped CeO 2 nanosheets with abundant oxygen vacancies were fabricated by exfoliation of the CeCO 3 OH precursor through calcination. 58 The incorporation of Co dopants induced the formation of oxygen vacancy on the CeO 2 nanosheets, which in turn enhance the active sites and lower the binding energy during HER.…”