Excess Activity Tuned by Distorted Tetrahedron in CoMoO_(4) for Oxygen Evolution

Oxygen vacancies enable modulating surface reconstruction of transition metal oxides containing metal-oxygen polyhedrons into metallic oxyhydroxide for oxygen evolution reaction(OER),while revealing reconstructing mechanism is stuck by the requirement to precisely control exact sites of these vacancies.Herein,oxygen vacancies are localized only within MoO_(4)tetrahedrons rather than CoO_(6)octahedrons in CoMoO_(4)catalyst,guaranteeing coherent reconstruction of CoO_(6)octahedrons into pure CoOOH with tunable activities for OER.Meanwhile,distorted tetrahedron accelerates the dissolution of Mo atoms into alkaline electrolyte,triggering spontaneous transition of partial CoMoO_(4)into Co(OH)_(2).CoO_(6)octahedrons in both CoMoO_(4)and Co(OH)_(2)can transform pure CoOOH completely at lower potential,resulting in excess intrinsic activity whose summit is identified by overpotential at 10 mA cm^(-2)with 22.9%reduction and Tafel slope with 65.3%reduction.Well-defined manipulation over the distorted polyhedrons offers one versatile knob to precisely modulate electronic structure of oxide catalysts with outstanding OER performance.

Electronic structure engineering of transition metal dichalcogenides for boosting hydrogen energy conversion electrocatalysts

Electrocatalytic water splitting for hydrogen production is an appealing strategy to reduce carbon emissions and generate renewable fuels.This promising process,however,is limited by its sluggish reaction kinetics and high-cost catalysts.The two-dimensional(2D)transition metal dichalcogenides(TMDCs)have presented great potential as electrocatalytic materials due to their tunable bandgaps,abundant defective active sites,and good chemical stability.Consequently,phase engineering,defect engineering and interface engineering have been adopted to manipulate the electronic structure of TMDCs for boosting their exceptional catalytic performance.Particularly,it is essential to clarify the local structure of catalytically active sites of TMDCs and their structural evolution in catalytic reactions using atomic resolution electron microscopy and the booming in situ technologies,which is beneficial for exploring the underlying reaction mechanism.In this review,the growth regulation,characterization,particularly atomic configurations of active sites in TMDCs are summarized.The significant role of electron microscopy in the understanding of the growth mechanism,the controlled synthesis and functional optimization of 2D TMDCs are discussed.This review will shed light on the design and synthesis of novel electrocatalysts with high performance,as well as prompt the application of advanced electron microscopy in the research of materials science.

The Recent Development of International Exchange Market and its Effects on China

1. The Key Points of Recent Development of International Exchange Market The unusual fluctuation of international exchange market lies in the following three facts： firstly, there are irreconcilable contradictions in current international monetary system, caused by USA which is the core of cttrrent int#rnational monetary system and has been carrying out irresponsible economic policies for a long time. Secondly, thel economic structure of USA loses balance seriously. Thirdly, the balance of payments （BP） becomes a tough problem for the USA government.

Recent advances of amorphous-phase-engineered metal-based catalysts for boosted electrocatalysis

Amorphous metal-based catalysts(AMCs)have sparked intense research interests in the field of electrocatalysis elicited by their hallmark features such as unlimited volume and morphology,manipulated electronic structures,enriched defects,and unsaturated surface atom coordination.Nevertheless,the manipulation of the amorphous phase in metal-based catalysts is so far impractical,and thus their electrocatalytic mechanism yet remains ambiguous.In this review,the latest advances in AMCs are systematically reviewed,covering amorphous-phase engineering strategy,structure manipulation,and amorphization of various material categories for electrocatalysis.Specifically,a series of applications of AMCs in electrocatalysis for the oxygen reduction reaction(ORR),hydrogen evolution reaction(HER),and oxygen evolution reaction(OER)are summarized based on the classification criteria of substances.Finally,we put forward current challenges that have not yet been clarified in the field of AMCs,and propose possible solutions,particularly from the perspective of the evolution of electron microscopy.It is expected to promote the understanding of the amorphization-catalysis relationship and provide a guideline for designing high-performance electrocatalysts.