Phase-mediated cobalt phosphide with unique core-shell architecture serving as efficient and bifunctional electrocatalyst for hydrogen evolution and oxygen reduction reaction

Advanced development of finite element analysis for electrochemical catalytic reactions

The development of robust simulation techniques is crucial for elucidating electrochemical catalytic mechanisms and can even provide guidance for the tailored design and regulation of highly efficient catalysts. Finite element analysis (FEA), as a powerful numerical simulation tool, can effectively simulate and analyze the sophisticated processes involved in electrochemical catalytic reactions and unveil the underlying microscopic mechanisms. By employing FEA, researchers can gain better insights into reaction kinetics and transport processes, optimize electrode design, and predict electrochemical performance under various reaction conditions. Consequently, the application of FEA in electrochemical catalytic reactions has emerged as a critical area of current research and a summary of the advanced development of FEA for electrochemical catalytic reactions is urgently required. This review focuses on exploring the applications of FEA in investigating the crystal structure effect, tip effect, multi-shell effect, porous structure effect, and mass transfer phenomena in electrochemical reactions. Particularly emphasized are its applications in the fields of CO2 reduction, oxygen evolution reaction, and nitrogen reduction reaction. Finally, the challenges encountered by this research field are discussed, along with future directions for further advancement. We aim to provide comprehensive theoretical and practical guidance on FEA methods for researchers in the field of electrochemical catalysis, thereby fostering the advancement and wider implementation of FEA within this domain.

Enhancing char formation of flame retardant epoxy composites: Onigiri-like ZIF-67 modification with carboxymethyl β-cyclodextrin crosslinking

To enhance char formation of flame retardant epoxy (EP) composites, carboxymethyl β-cyclodextrin (CM-β-CD) is employed as an etchant for or ZIF-67 derivatives. In the early stage, etching plays a dominant role. The mismatch in size between CM-β-CD opening and ZIF-67 pore leads to the stacking of carboxyl cobalt complexes on the shell. When the reaction time is prolonged, crosslinking occurs between carboxyl and hydroxyl groups. Crosslinked CM-β-CD weakens and eventually stops the etching process. Triethyl phosphate (TEP), an additive to improve flame retardancy, is also absorbed on the shell in this one-pot synthesis. Herin, the synthesis of metal-organic framework (MOF) derivatives can impart multiple functions to MOF. This novel nanohybrid significantly improved flame retardancy of EP composites with only 2.0 wt% loading. The peak heat release rate (pHRR) and total smoke production (TSP) were reduced by 54.8 and 46.9%, respectively. The integrated multi-element system resulted in an expanded and reinforced char layer. This study proposes a simple and precise method for controlling the structure of MOF-carbohydrate hybrids through competition between chemical reactions.

Amorphous and defective Co-P-O@NC ball-in-ball hollow structure for highly efficient electrocatalytic overall water splitting

Electrochemical water splitting using hollow and defect-rich catalysts has emerged as a promising strategy for efficient hydrogen production. However, the rational design and controllable synthesis of such catalysts with intricate morphology and composition present significant challenges. Herein, we propose a template-engaged approach to fabricate a novel ball-in-ball hollow structure of Co-P-O@N-doped carbon with abundant oxygen vacancies. The synthesis process involves the preparation of uniform cobalt-glycerate (Co-gly) polymer microspheres as precursors, followed by surface coating with ZIF-67 layer, adjustable chemical etching by phytic acid, and controllable pyrolysis at high temperature. The resulting ball-in-ball structure offers a large number of accessible active sites and high redox reaction centers, facilitating efficient charge transport, mass transfer, and gas evolution, which are beneficial for the acceleration of electrocatalytic reaction. Additionally, density functional theory (DFT) calculations indicate that the incorporation of oxygen and the presence of Co-P dangling bonds in CoP significantly enhance the adsorption of oxygenated species, leading to improved intrinsic electroactivity at the single-site level. As a sequence, the titled catalyst exhibits remarkable electrocatalytic activity and stability for water splitting in alkaline media. Notably, it only requires a low overpotential of 283 mV to achieve a current density of 10 mA cm^-2 for the oxygen evolution reaction. This work may provide some new insights into the design of complex hollow structures of phosphides with abundant defects for energy conversion.