Microwave-assisted exploration of the electron configuration-dependent electrocatalytic urea oxidation activity of 2D porous NiCo_(2)O_(4) spinel

Urea holds promise as an alternative water-oxidation substrate in electrolytic cells.High-valence nickelbased spinel,especially after heteroatom doping,excels in urea oxidation reactions(UOR).However,traditional spinel synthesis methods with prolonged high-temperature reactions lack kinetic precision,hindering the balance between controlled doping and highly active two-dimensional(2D)porous structures design.This significantly impedes the identification of electron configuration-dependent active sites in doped 2D nickel-based spinels.Herein,we present a microwave shock method for the preparation of 2D porous NiCo_(2)O_(4)spinel.Utilizing the transient on-off property of microwave pulses for precise heteroatom doping and 2D porous structural design,non-metal doping(boron,phosphorus,and sulfur)with distinct extranuclear electron disparities serves as straightforward examples for investigation.Precise tuning of lattice parameter reveals the impact of covalent bond strength on NiCo_(2)O_(4)structural stability.The introduced defect levels induce unpaired d-electrons in transition metals,enhancing the adsorption of electron-donating amino groups in urea molecules.Simultaneously,Bode plots confirm the impact mechanism of rapid electron migration caused by reduced band gaps on UOR activity.The prepared phosphorus-doped 2D porous NiCo_(2)O_(4),with optimal electron configuration control,outperforms most reported spinels.This controlled modification strategy advances understanding theoretical structure-activity mechanisms of high-performance 2D spinels in UOR.

Microwave shock motivating the Sr substitution of 2D porous GdFeO_(3) perovskite for highly active oxygen evolution

The incorporation of partial A-site substitution in perovskite oxides represents a promising strategy for precisely controlling the electronic configuration and enhancing its intrinsic catalytic activity.Conventional methods for A-site substitution typically involve prolonged high-temperature processes.While these processes promote the development of unique nanostructures with highly exposed active sites,they often result in the uncontrolled configuration of introduced elements.Herein,we present a novel approach for synthesizing two-dimensional(2D)porous GdFeO_(3) perovskite with A-site strontium(Sr)substitution utilizing microwave shock method.This technique enables precise control of the Sr content and simultaneous construction of 2D porous structures in one step,capitalizing on the advantages of rapid heating and cooling(temperature~1100 K,rate~70 K s^(-1)).The active sites of this oxygen-rich defect structure can be clearly revealed through the simulation of the electronic configuration and the comprehensive analysis of the crystal structure.For electrocatalytic oxygen evolution reaction application,the synthesized 2D porous Gd_(0.8)Sr_(0.2)FeO_(3) electrocatalyst exhibits an exceptional overpotential of 294 mV at a current density of 10 mA cm^(-2)and a small Tafel slope of 55.85 mV dec^(-1)in alkaline electrolytes.This study offers a fresh perspective on designing crystal configurations and the construction of nanostructures in perovskite.

Metastable Two-Dimensional Materials for Electrocatalytic Energy Conversions

CONSPECTUS:An urgent need for efficient energy conversion technologies is driving development of active and durable electrocatalysts.In recent years,two-dimensional(2D)materials have emerged as practically promising electrocatalysts because of unique physical and chemical properties.In general,a significant proportion of 2D materials are polymorphous with diverse crystal structures or stoichiometry.However,pristine 2D materials found in nature are thermodynamically stable phases with inert catalytic activity.Metastable phases,in contrast,are highly active for various electrocatalytic processes because of high-energy structures and high reactivity of nonequilibrium surfaces.Generally,the growth of metastable 2D materials requires higher formation energy compared with the thermodynamically stable phases,which are difficultly obtained in standard synthetic processes such as chemical vapor deposition and vapor transport processes.The destabilization of thermodynamically stable 2D materials via external forces facilitates the conversion of highentropy crystal structure into metastable phases.To date,a number of approaches,including confined growth,topotactic transformation,electron donating,and chemical exfoliation,have been demonstrated for the preparation of high-performance metastable 2D electrocatalysts.As an atomic thin platform,metastable 2D materials represent an almost ideal prototype to achieve a comprehensive understanding of the fundamental principles and mechanisms of various electrocatalytic processes.In the design of metastable 2D electrocatalysts,a number of needs must be concomitantly considered,namely,(1)economic of synthesis methods,(2)product yield,(3)applicability of post-treatment for tuning electrocatalytic properties,(4)general synthesis protocols,and(5)the chemical and catalytic stabilities of metastable 2D materials.In this Account,we provide a critical and timely overview of metastable 2D materials for major electrocatalytic energy conversions based on recent research in our group.We review unique advances and challenges with metastable 2D materials,including specific design principles and typical strategies for synthesis of metastable 2D nanostructured materials with desirable characteristics.We compare advances in metastable 2D materials in selected electrocatalytic processes from fundamental through to functional.Significant emphasis is placed on design strategies for metastable 2D materials and resultant influence on intrinsic electrocatalytic performance,including electronic properties and adsorption energetics.We conclude with an appraisal of the likely opportunities and difficulties with metastable 2D electrocatalysts at the atomic level.This Account provides understandings and insights to the research of metastable 2D electrocatalysts.The current achievements of metastable 2D materials with the ultimate target of synthesizing high performance electrocatalysts may facilitate the development of heterogeneous catalysis for clean energy applications.