MOF-mediated synthesis of novel PtFeCoNiMn high-entropy nanoalloy as bifunctional oxygen electrocatalysts for zinc-air battery

High-entropy alloy(HEA)-based materials are expected to be promising oxygen electrocatalysts due to their exceptional properties.The electronic structure regulation of HEAs plays a pivotal role in enhancing their elctrocatalytic ability.Herein,PtFeCoNiMn nanoparticles(NPs)with subtle lattice distortions are constructed on metal-organic framework-derived nitrogen-doped carbon by an ultra-rapid Joule heating process.Thanks to the modulated electronic structure and the inherent cocktail effect of HEAs,the as-synthesized PtFeCoNiMn/NC exhibits superior bifunctional electrocatalytic performance with a positive half-wave potential of 0.863 V vs.reversible hydrogen electrode(RHE)for oxygen reduction reaction and a low overpotential of 357 mV at 10 mA·cm^(-2)for oxygen evolution reaction.The assembled quasi-solid-state zinc-air battery using PtFeCoNiMn/NC as air electrode shows a high peak power density of 192.16 mW·cm^(-2),low charge−discharge voltage gap,and excellent durability over 500 cycles at 5 mA·cm^(-2).This work demonstrates an effective route for rational design of bifunctional nanostructured HEA electrocatalysts with favorable electronic structures,and opens up a fascinating directions for energy storage and conversion,and beyond.

Large-scale synthesis of low-cost 2D metal–organic frameworks for highly selective photocatalytic CO_(2)reduction

Two-dimensional metal–organic frameworks(2D MOFs),as a new type of 2D materials,have been widely applied in various applications because of their unique structures and exposed active sites.Herein,we reported two low-cost 2D MOFs constructed by a raw chemical succinic acid(SA),M-SA(M=Ni or Co),which served as efficient photocatalysts for the reduction of CO_(2)to CO.Taking advantage of the thinness and open metal sites,the ultrathin Ni-SA nanosheets(ca.3.6 nm)exhibited excellent CO production of 6.96(7)mmol·g^(−1)·h^(−1)and CO selectivity of 96.6%.Photoelectrochemical tests and theoretical calculations further confirmed the higher charge transfer efficiency and unsaturated metal sites for promoting photocatalytic performances.More importantly,Ni-SA can also be synthesized in large-scale by an energy-saving method under room temperature,strongly suggesting its promising future and potential for practical applications.

A 3D hierarchical electrocatalyst:Core–shell Cu@Cu(OH)_(2)nanorods/MOF octahedra supported on N-doped carbon for oxygen evolution reaction

Cu-based materials are seldom reported as oxygen evolution reaction(OER)electrocatalysts due to their inherent electron orbital configuration,which makes them difficult to adsorb oxygen-intermediates during OER.Reasonably engineering the hierarchical architectures and the electronic structures can improve the performance of Cu-based OER catalysts,such as constructing multilevel morphology,inducing the porous materials,improving the Cu valence,building heterostructures,doping heteroatoms,etc.In this work,copper-1,3,5-benzenetricarboxylate(HKUST-1)octahedra in-situ grow on the Cu nanorod(NR)-supported N-doped carbon microplates,meanwhile an active layer of Cu(OH)_(2)forms on the surface of the original conductive Cu NRs.The octahedral HKUST-1,serving as a spacer between the microplates,greatly improves the porosity and increases the available active sites,facilitating the mass transport and electron transfer,thus resulting in greatly enhanced OER performance.

MOF衍生的磷化钴纳米纤维用于电催化氧析出和氢析出反应

高性能催化剂的开发和利用是能源领域的研究热点,其中制备具有高活性面积的一维纳米催化剂是目前的难点.本研究以金属有机框架(MOF)复合纤维为前驱体,通过热处理-磷化过程制备了具有氧析出(OER)和氢析出(HER)双功能特性的CoP纳米纤维.该MOF衍生策略也可以用来制备其他一维纳米材料,如Co_(3)O_(4)纳米纤维、Co/C纤维和CoP/C复合纤维.研究表明,CoP纳米纤维的直径约100 nm,长度可达几微米,具有较高的活性面积.通过Cu掺杂改性可以提高CoP纳米纤维的催化活性,碱性条件下测得其对OER和HER的过电位分别为330和170 mV,可与商业的贵金属催化剂相媲美.该工作也为一维双功能电极催化剂的制备及功能化提供了研究基础.

Si Doping-Induced Electronic Structure Regulation of Single-Atom Fe Sites for Boosted CO_(2) Electroreduction at Low Overpotentials

Transition metal-based single-atom catalysts(TM-SACs)are promising alternatives to Au-and Ag-based electrocatalysts for CO production through CO_(2)reduction reaction.However,developing TM-SACs with high activity and selectivity at low overpotentials is challenging.Herein,a novel Fe-based SAC with Si doping(Fe-N-C-Si)was prepared,which shows a record-high electrocatalytic performance toward the CO_(2)-to-CO conversion with exceptional current density(>350.0 mA cm^(−2))and~100%Faradaic efficiency(FE)at the overpotential of<400 mV,far superior to the reported Fe-based SACs.Further assembling Fe-N-C-Si as the cathode in a rechargeable Zn-CO_(2)battery delivers an outstanding performance with a maximal power density of 2.44 mW cm^(−2)at an output voltage of 0.30 V,as well as high cycling stability and FE(>90%)for CO production.Experimental combined with theoretical analysis unraveled that the nearby Si dopants in the form of Si-C/N bonds modulate the electronic structure of the atomic Fe sites in Fe-N-C-Si to markedly accelerate the key pathway involving^(*)CO intermediate desorption,inhibiting the poisoning of the Fe sites under high CO coverage and thus boosting the CO_(2)RR performance.This work provides an efficient strategy to tune the adsorption/desorption behaviors of intermediates on singleatom sites to improve their electrocatalytic performance.