A fast and in-depth self-reconstruction of anion ligands optimized CoFe-based pre-catalysts for water oxidation

The design of efficient and robust non-precious metal electrocatalysts towards oxygen evolution reaction(OER)is of great value for developing green energy technologies.The in-situ formed high-valence(oxy)hydroxides species during the reconstruction process of pre-catalysts are recognized as the real contributing sites for OER.However,pre-catalysts generally undergo a slow and inadequate self-reconstruction.Herein,we reported a PO^(3-)_(4)optimized CoFe-based OER catalysts with amorphous structure,which enables a fast and deep reconstruction during the OER process.The amorphous structure induced by ligands PO^(3-)_(4)is prone to evolution and further form active species for OER.The electron interaction between metal sites can be modulated by electron-rich PO^(3-)_(4),which promotes generation of high active CoOOH.Simultaneously,the etching of PO^(3-)_(4)from the pre-catalysts during the catalytic process is in favor of accelerating the self-reconstruction.As a result,as-prepared precatalyst can generate high active CoOOH at a low potential of 1.4 V and achieve an in-depth reconstructed nanosheet structure with abundant OER active sites.Our work provides a promising design of pre-catalysts for realizing efficient catalysis of water oxidation.

In-situ assembly of 2D/3D porous nickel cobalt sulfide solid solution as superior pre-catalysts to boost multi-functional electrocatalytic oxidation

In this work,we fabricated an efficient pre-catalyst based on(Ni,Co)S2solid solution with hierarchical architecture and high porosity to boost urea oxidation reaction and electrocatalytic oxidation of organic small molecules.The interaction between Ni and Co can optimize the electronic structure,resulting in the improved conductivity and accelerated charge transfer rate.The 2D/3D architecture can enrich more active species and endow the mass and electron transport to facilitate the surface oxidation and the following catalytic process.Post-structure and catalytic characterizations confirm the surface oxidation of(Ni,Co)S_(2)during the stability test,and the in-situ formed Co(Ni)based(oxy)hydroxides exhibit superior catalytic activity and facilitated charge transfer ability.As a result,the optimal(Ni,Co)S_(2)solid solution pre-catalyst displays facilitated catalytic behavior and good stability for multifunctional electrocatalytic oxidation,in which a high conversion of benzyl alcohol(97.50%),a good selectivity to benzoic acid(93.78%)and a satisfied faraday efficiency(91.86%)can be achieved.

Self-templated formation of twin-like metal-organic framework nanobricks as pre-catalysts for efficient water oxidation

Fabrication of single-crystalline metal-organic framework(MOF)hollow nanostructures with two-dimensional(2D)morphologies is a challenging task.Herein,twin-like MOF nanobricks,a quasi-hollow 2D architecture,with multi-metal nodes and replaceable organic ligands,are uniformly and firmly grown on conductive Ni foam through a generic one-pot approach.The formation process of twin-like MOF nanobricks mainly includes selective epitaxial growth of Fe-rich MOF layer and simultaneously dissolution of the pre-formed Ni-rich metal-organic frameworks(MOFs),all of which can be ascribed to a special self-templated mechanism.The fantastic structural merits of twin-like MOF nanobrick arrays,featuring highly exposed active sites,remarkable electrical conductivity,and hierarchical porosities,enable this material for efficient electrocatalysis.Using bimetallic NiFe-MOFs grown on Ni foam as an example,the resultant twin-like nanobrick arrays can be directly utilized as three-dimensional(3D)integrated electrode for high-performance water oxidation in 1 M KOH with a low overpotential,fast reaction kinetics(28.5 mV·dec^(-1)),and superb stability.Interestingly,the unstable NiFe-MOFs were served as an oxygen evolution reaction(OER)pre-catalyst and the single-crystalline NiFe-MOF precursor can be in-situ topochemically regulated into porous and lowcrystalline NiFeOx nanosheets during the OER process.This work extends the hollowing strategy to fabricate hollow MOFs with 2D architectures and highlights their direct utilization for advanced electrocatalysis.

Electrocatalytic oxygen evolution activities of metal chalcogenides and phosphides:Fundamentals,origins,and future strategies

The development of inexpensive and efficient electrocatalysts is key to commercializing energy-related electrocatalytic techniques such as water electrolyzers and metal-air batteries.In particular,novel oxygen evolution reaction(OER)pre-catalysts,such as transition metal chalcogenides(TMCs)and phosphides(TMPs),have evolved in recent years from traditional stable OER electrocatalysts,which show superior OER electrocatalytic performance compared with transition metal oxides(TMOs)or(oxy)hydroxides(TMOHs).In this feature article,we summarize recent advances in the development of TMCand TMP-based OER electrocatalysts,as well as approaches to improve the OER performance in terms of morphology,structure,composition,surface engineering,lattice-strained and in-situ transformation in the electrolysis process.In particular,the electrochemical stability of TMCs and TMPs in alkaline electrolytes and the evolution of morphology,structure and composition under OER conditions are discussed.In the last section,we discuss the challenges that need to be addressed in this specific area of research and the implications for further research.

In-situ transformed trimetallic metal-organic frameworks as an efficient pre-catalyst for electrocatalytic oxygen evolution

Developing high-efficiency and low-cost oxygen evolution reaction(OER)catalysts is crucial to advance the water splitting technology for sustainable hydrogen production.Here,a FeCoNi coordinated benzene-1,3,5-tricarboxylic acid(FeCoNiBTC)metal-organic framework(MOF)was synthesized by one-step solvothermal method for OER.A rapid in-situ chemical and electrochemical transformation was observed on the surface of the FeCoNiBTC MOF during OER process.The formed catalytic active FeCoNiOx(OH)y species retained the unique structure feature of initial FeCoNiBTC,moreover,it possessed multiple transition metal active nodes that cooperate with each other to adjust the electronic structure.Owing to the above structure advantages,the in-situ transformed FeCoNiOx(OH)y showed excellent OER catalytic activity with a small overpotential of 230 mV to achieve the 100 mA·cm^(−2),a low Tafel slope of 50.2 mV·dec^(−1),and superior stability of almost 80 h in alkaline aqueous solution.This work systematically studies the structure-performance relations of the multi-metal MOF-based materials in OER process,and it would enrich the exploration of highly efficient OER electrocatalysts.

High-Performanceα-Diimine Nickel Complexes for Facile Access of PE Elastomers with Exceptional Material Properties

For practicable elastomeric polyethylene,achieving high catalyst thermal stability and activity,along with precise control of polymer properties such as branching density,molecular weights,and distribution,is crucial but challenging.In this study,two sets of symmetricalα-diimine nickel complexes,each comprising four nickel bromide or chloride complexes,were synthesized and investigated their performance for ethylene polymerization under various reaction conditions.Upon activation with either Et2AlCl or MMAO cocatalysts,these complexes displayed not only high activity but also generated high molecular weight polyethylenes with controlled polydispersity and a substantial number of branches.The catalyst with the least steric hindrance displayed the remarkable high activity(up to 1.2×10^(7) g·mol^(-1)·h^(-1)).Notably,nickel bromides demonstrated higher activity compared to their chloride counterparts.The investigation into the effect of reaction temperature on catalytic performance revealed that NiBrMe-MMAO system displayed high thermal stability(activity up to 2.51×10^(6) g·mol^(-1)·h^(-1) at 100℃)and consistently yielded high polymer molecular weights with narrow polydispersity over a broad temperature range of 30-100℃.Of significant note,mechanical analysis of the resulting polyethylene demonstrated excellent ultimate tensile strength and high strain at break.Particularly,the polyethylene sample prepared at 100℃exhibited ultimate tensile strength up to 10 MPa with 1863%maximum strain at break and a strain recovery of up to 54.9%after ten cycles at a fixed strain of 300%,indicating excellent material properties of prepared thermoplastic polyethylene elastomers(TPE).