Vacancy Promotion in Layered Double Hydroxide Electrocatalysts for Improved Oxygen Evolution Reaction Performance

Abstract

Layered double hydroxides (LDHs) are promising catalysts for the oxygen evolution reaction (OER) given their modular chemistry and ease of synthesis. Herein, we report a facile strategy for inclusion of oxygen vacancies (VO) using Ce as a promoter in Co–Ni LDHs that significantly enhances the activity for OER. In situ X-ray absorption spectroscopy (XAS) uncovers an increase in octahedral Co sites and VO upon addition of Ce that promotes the transformation of the LDH into an oxyhydroxide-reactive phase more readily. The presence of an OER-active oxyhydroxide phase along with the generation of VO facilitated by the partial reduction of Ce4+ to Ce3+ under oxidizing conditions results in a better electrochemical activity of Ce-doped electrocatalysts. Density functional theory calculations further corroborate the in situ XAS experimental findings by showcasing that the presence of both Ce and VO reduces the free-energy barrier of the rate-limiting OH* deprotonation step during OER. This work showcases how an enhanced understanding of the role of VO promoters in LDH electrocatalysts can provide insights for future catalyst design in anodic reactions.

Enhanced uranium extraction selectivity from seawater using dopant engineered layered double hydroxides

“…MgAl based LDHs were synthesized using established co-precipitation method. 24,25 To synthesize LDH with M 2+ : M 3+ cation ratio 3 : 1, first 4.5 mmol Mg 2+ (magnesium nitrate hexahydrate) and 1.5 mmol Al 3+ (aluminium nitrate nonahydrate) were dissolved in 5 ml deionised water. Then, 50 ml of 0.3 M NaOH solution was added slowly into the metal precursor solution while stirring, keeping pH in the range of 10–14.…”

“…22 Advantages of LDHs include ease of preparation and highly tailorable properties. 19,20,23–25 The versatility in the chemistry in LDHs thus enables property/structure manipulation that could be tuned to target adsorbates of interest. Indeed, LDHs with varying chemistries (MgAl, MgFe, CaAl and others, with different interlayer anions) have previously demonstrated fast and efficient adsorption of U from wastewater and seawater solutions.…”

Toward Understanding the Formation Mechanism and OER Catalytic Mechanism of Hydroxides by In Situ and Operando Techniques

“…For instance, Bedford et al presented a simple approach to introduce oxygen vacancies (V O ) in CoNi-LDHs by employing Ce as a promoter that significantly enhances the catalytic activity for the OER. [83] In situ XAS reveals an increase in octahedral Co sites and V O upon the addition of Ce that promotes the transformation of the LDH into an oxyhydroxide-reactive phase more readily. The incorporation of Ce and the generation of V O facilitated by the partial reduction of Ce 4 + to Ce 3 + under oxidizing conditions result in improved electrochemical activity of the Ce-doped electrocatalysts.…”

C60 and Derivatives Boost Electrocatalysis and Photocatalysis: Electron Buffers to Heterojunctions

“…More advanced characterization methods will be important in developing a quantitative understanding of constitutive relationships in catalysts including, active sites, mechanism(s) for heterojunction formation and electronic structure(s) in C 60 composites, [219][220][221][222] because it is acknowledged established techniques for, particularly, analyzing intricate structure of C 60 composites appear inadequate. [223] Additionally, heterojunction techniques including, Type-II heterojunctions, Z-Scheme heterojunctions and S-Scheme heterojunctions can be problematic in a practical setting.…”