Exciting lattice oxygen of nickel–iron bi-metal alkoxide for efficient electrochemical oxygen evolution reaction

High efficiency,cost-effective and durable electrocatalysts are of pivotal importance in energy conversion and storage systems.The electro-oxidation of water to oxygen plays a crucial role in such energy conversion technologies.Herein,we report a robust method for the synthesis of a bimetallic alkoxide for efficient oxygen evolution reaction(OER)for alkaline electrolysis,which yields current density of 10 mA cm^(-2)at an overpotential of 215 mV in 0.1 M KOH electrolyte.The catalyst demonstrates an excellent durability for more than 540 h operation with negligible degradation in activity.Raman spectra revealed that the catalyst underwent structure reconstruction during OER,evolving into oxyhydroxide,which was the active site proceeding OER in alkaline electrolyte.In-situ synchrotron X-ray absorption experiment combined with density functional theory calculation suggests a lattice oxygen involved electrocatalytic reaction mechanism for the in-situ generated nickel–iron bimetal-oxyhydroxide catalyst.This mechanism together with the synergy between nickel and iron are responsible for the enhanced catalytic activity and durability.These findings provide promising strategies for the rational design of nonnoble metal OER catalysts.

Organic cathode materials for rechargeable magnesium-ion batteries:Fundamentals, recent advances, and approaches to optimization

Rechargeable magnesium-ion batteries(MIBs) are favorable substitutes for conventional lithium-ion batteries(LIBs) because of abundant magnesium reserves, a high theoretical energy density, and great inherent safety. Organic electrode materials with excellent structural tunability,unique coordination reaction mechanisms, and environmental friendliness offer great potential to promote the electrochemical performance of MIBs. However, research on organic magnesium battery cathode materials is still preliminary with many significant challenges to be resolved including low electrical conductivity and unwanted but severe dissolution in useful electrolytes. Herein, we provide a detailed overview of reported organic cathode materials for MIBs. We begin with basic properties such as charge storage mechanisms(e.g., n-, p-, and bipolartype), moving to recent advances in various types of organic cathodes including carbonyl-, nitrogen-, and sulfur-based materials. To shed light on the diverse strategies targeting high-performance Mg-organic batteries, elaborate summaries of various approaches are presented.Generally, these strategies include molecular design, polymerization, mixing with carbon, nanosizing and electrolyte/separator optimization.This review provides insights on exploring high-performance organic cathodes in rechargeable MIBs.

Oxygen Vacancy-Rich 2D TiO_(2) Nanosheets:A Bridge Toward High Stability and Rapid Hydrogen Storage Kinetics of Nano-Confined MgH_(2)

MgH_(2) has attracted intensive interests as one of the most promising hydrogen storage materials.Nevertheless,the high desorption temperature,sluggish kinetics,and rapid capacity decay hamper its commercial application.Herein,2D TiO_(2) nanosheets with abundant oxygen vacancies are used to fabricate a flower-like MgH_(2)/TiO_(2) heterostructure with enhanced hydrogen storage performances.Particularly,the onset hydrogen desorption temperature of the MgH_(2)/TiO_(2) heterostructure is lowered down to 180℃(295℃ for blank MgH_(2)).The initial desorption rate of MgH_(2)/TiO_(2) reaches 2.116 wt% min^(-1) at 300℃,35 times of the blank MgH_(2) under the same conditions.Moreover,the capacity retention is as high as 98.5% after 100 cycles at 300℃,remarkably higher than those of the previously reported MgH_(2)-TiO_(2) composites.Both in situ HRTEM observations and ex situ XPS analyses confirm that the synergistic effects from multi-valance of Ti species,accelerated electron transportation caused by oxygen vacancies,formation of catalytic Mg-Ti oxides,and stabilized MgH_(2) NPs confined by TiO_(2) nanosheets contribute to the high stability and kinetically accelerated hydrogen storage performances of the composite.The strategy of using 2D substrates with abundant defects to support nano-sized energy storage materials to build heterostructure is therefore promising for the design of high-performance energy materials.

In-situ transformed Mott-Schottky heterointerface in silver/manganese oxide nanorods boosting oxygen reduction,oxygen evolution,and hydrogen evolution reactions

The development of non-platinum group metal(non-PGM)and efficient multifunctional electrocatalysts for oxygen reduction reaction(ORR),oxygen evolution reaction(OER),and hydrogen evolution reaction(HER)with high activity and stability remains a great challenge.Herein,by in-situ transforming silver manganese composite oxide heterointerface into boosted Mott-Schottky heterointerface through a facile carbon reduction strategy,a nanorod-like silver/manganese oxide with superior multifunctional catalytic activities for ORR,OER and HER and stability was obtained.The nanorod-like silver/manganese oxide with Mott-Schottky heterointerface(designated as Ag/Mn_(3)O_(4))exhibits an ORR half-wave potential of 0.831 V(vs.RHE)in 0.1 M KOH,an OER overpotential of 338 mV and a HER overpotential of 177 mV at the current density of 10 mA·cm^(-2)in 1 M KOH,contributing to its noble-metal benchmarks comparable performance in aqueous aluminum-air(Al-air)battery and laboratorial overall water splitting electrolytic cell.Moreover,in-situ electrochemical Raman and synchrotron radiation spectroscopic measurements were conducted to further illustrate the catalytic mechanism of Ag/Mn_(3)O_(4)Mott-Schottky heterointerface towards various electrocatalytic reactions.At the heterointerface,the Ag phase serves as the electron donor and the active phase for ORR and HER,while the Mn_(3)O_(4)phase serves as the electron acceptor and the active phase for OER,respectively.This work deepens the understanding of the Mott-Schottky effect on electrocatalysis and fills in the gap in fundamental physical principles that are behind measured electrocatalytic activity,which offers substantial implications for the rational design of cost-effective multifunctional electrocatalysts with Mott-Schottky effect.