First-row(3d)transition metal oxyhydroxides have attracted increasing attention due to their various advantages.Although investigating the oxidation mechanism and processing such materials into hierar-chical architectures are greatly desired for their further development,it remains unclear how the oxida-tion state change occurs,and efforts to produce hierarchical oxyhydroxides in compliance with high ecological and economic standards have progressed slowly.Here,we describe a facile one-step coprecip-itation route for the preparation of hierarchical CoOOH,NiOOH and MnOOH,which involves the diffusion of NH3 originating from ammonium hydroxide solution into an aqueous solution containing metal ion salts and K2S2O8.Comprehensive characterizations by scanning electron microscope,transmission elec-tron microscopy,X-ray diffraction analysis,X-ray photoelectron spectroscopy,ultraviolet-visible spec-troscopy and in situ pH measurement demonstrated that K2S2O8 induces the oxidation state change of metal ion species after the start of hydrolysis.Meanwhile,it was found that,benefiting from the OH-con-centration gradient created by the NH3 diffusion method and the suitable growth environment provided by the presence of K2S2O8(high nucleation rate and secondary nucleation),the formation of hierarchical oxyhydroxide structures can be realized in aqueous solution at ambient temperature without the use of heat energy and additional structure-directing agents.The hierarchical CoOOH structures are performed as the electrocatalysts for the oxygen evolution reaction in alkaline media,which exhibit good activity with an overpotential of 320 mV at 10 mA cm-2 and a low Tafel slope of 59.6 mV dec-1,outperforming many congeneric electrocatalysts.Overall,our study not only provides important insights to understand the formation mechanism of hierarchical oxyhydroxides,but also opens up new opportunities for the preparation of hierarchical oxyhydroxides via a facile,green and low-cost method.

University of Konstanz,Physical Chemistry,Universit?tsstraβe 10,Konstanz D-78457,Germany;School of Materials Science and Engineering,Ocean University of China,Qingdao 266100,Shandong,China

[1]Zongkun Chen;Xingkun Wang;Sascha Ke?ler;Qiqi Fan;Minghua Huang;Helmut C?lfen-.Synthesis of hierarchical transition metal oxyhydroxides in aqueous solution at ambient temperature and their application as OER electrocatalysts)[J].能源化学,2022(08):89-97

coprecip,oxyhydroxide

Synthesis,hierarchical,transition,metal,oxyhydroxides,aqueous,solution,ambient,temperature,their,application,OER,electrocatalysts,First,3d,have,attracted,increasing,attention,due,various,advantages,Although,investigating,oxidation,mechanism,processing,such,materials,into,architectures,are,greatly,desired,further,development,remains,unclear,how,state,change,occurs,efforts,produce,compliance,high,ecological,economic,standards,progressed,slowly,Here,we,describe,facile,one,step,itation,route,preparation,CoOOH,NiOOH,MnOOH,which,involves,diffusion,NH3,originating,from,ammonium,containing,salts,K2S2O8,Comprehensive,characterizations,by,scanning,microscope,transmission,microscopy,ray,diffraction,analysis,photoelectron,spectroscopy,ultraviolet,visible,situ,measurement,demonstrated,that,induces,species,after,start,hydrolysis,Meanwhile,was,found,benefiting,centration,gradient,created,method,suitable,growth,environment,provided,presence,nucleation,secondary,formation,structures,realized,without,use,heat,energy,additional,directing,agents,performed,oxygen,evolution,reaction,alkaline,media,exhibit,good,activity,overpotential,mV,mA,Tafel,slope,dec,outperforming,many,congeneric,Overall,our,study,not,only,provides,important,insights,understand,but,also,opens,up,new,opportunities,via,green,cost

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