The oxygen evolution reaction(OER)is a half-reaction of water electrolysis,and the OER performance of an electrocatalyst is significantly related to its energy conversion efficiency.Due to their high OER activity,tran...The oxygen evolution reaction(OER)is a half-reaction of water electrolysis,and the OER performance of an electrocatalyst is significantly related to its energy conversion efficiency.Due to their high OER activity,transition metal-based nanomaterials have become potential low-cost substitutes for Ir/Ru-based OER electrocatalysts in an alkaline environment.Herein,holey Fe3O4-coupled Ni(OH)2 sheets(Ni(OH)2-Fe H-STs)were easily achieved by a simple mixed-cyanogel hydrolysis strategy.The two-dimensional(2D)Ni(OH)2-Fe H-STs with ca.1 nm thickness have a high specific surface area,abundant unsaturated coordination atoms,and numerous pores,which are highly favorable for electrocatalytic reactions.Meanwhile,the introduction of Fe improves the conductivity and regulates the electronic structure of Ni.Due to their special structural features and synergistic effect between the Fe and Ni atoms,Ni(OH)2-Fe H-STs with an optimal Ni/Fe ratio show excellent OER activity in a 1 M KOH solution,which significantly exceeds that of the commercial RuO2 nanoparticle electrocatalyst.Furthermore,Ni(OH)2-Fe H-STs can be grown on nickel foam(NF),and the resulting material exhibits enhanced OER activity,such as a small overpotential of 200 mV and a small Tafel slope of 56 mV dec−1,than that of Ni(OH)2-Fe H-STs without NF.展开更多
Tortuosity is an important parameter for char- acterizing transport properties within porous materials and is of interest in a broad range of fields, such as energy storage and conversion materials. One of the paramet...Tortuosity is an important parameter for char- acterizing transport properties within porous materials and is of interest in a broad range of fields, such as energy storage and conversion materials. One of the parameters that impacts the tortuosity value is the geometry of the solid phase which, in this study, is considered as stochas- tically-placed rectangular particles. Through lattice Boltz- mann modelling （LBM）, we determined the impact of particle aspect ratio on the intrinsic tortuosity-porosity relationships of two-dimensional porous media composed of rectangular particles. These relationships were isolated for materials with grain （particle） aspect ratios of e { 1, 2, 3 } and porosities from [0.55 - 0.95]. We determined that a minimum of 6, 8 and 10 stochastic simulations, respec- tively, were required to calculate these average tortuosity values in laminar flow （Re 〈〈 1）. This novel application of the LBM to study the effects of porosity and aspect ratio of rectangular grains on tortuosity can be used in the tailoring of materials for clean energy.展开更多
文摘The oxygen evolution reaction(OER)is a half-reaction of water electrolysis,and the OER performance of an electrocatalyst is significantly related to its energy conversion efficiency.Due to their high OER activity,transition metal-based nanomaterials have become potential low-cost substitutes for Ir/Ru-based OER electrocatalysts in an alkaline environment.Herein,holey Fe3O4-coupled Ni(OH)2 sheets(Ni(OH)2-Fe H-STs)were easily achieved by a simple mixed-cyanogel hydrolysis strategy.The two-dimensional(2D)Ni(OH)2-Fe H-STs with ca.1 nm thickness have a high specific surface area,abundant unsaturated coordination atoms,and numerous pores,which are highly favorable for electrocatalytic reactions.Meanwhile,the introduction of Fe improves the conductivity and regulates the electronic structure of Ni.Due to their special structural features and synergistic effect between the Fe and Ni atoms,Ni(OH)2-Fe H-STs with an optimal Ni/Fe ratio show excellent OER activity in a 1 M KOH solution,which significantly exceeds that of the commercial RuO2 nanoparticle electrocatalyst.Furthermore,Ni(OH)2-Fe H-STs can be grown on nickel foam(NF),and the resulting material exhibits enhanced OER activity,such as a small overpotential of 200 mV and a small Tafel slope of 56 mV dec−1,than that of Ni(OH)2-Fe H-STs without NF.
基金the financial support from Carbon Management Canada Inc. (CMC)Canada Foundation for Innovation (CFI)+2 种基金Natural Sciences and Engineering Research Council of Canada (NSERC)the NSERC Canada Research Chairs Programthe University of Toronto
文摘Tortuosity is an important parameter for char- acterizing transport properties within porous materials and is of interest in a broad range of fields, such as energy storage and conversion materials. One of the parameters that impacts the tortuosity value is the geometry of the solid phase which, in this study, is considered as stochas- tically-placed rectangular particles. Through lattice Boltz- mann modelling （LBM）, we determined the impact of particle aspect ratio on the intrinsic tortuosity-porosity relationships of two-dimensional porous media composed of rectangular particles. These relationships were isolated for materials with grain （particle） aspect ratios of e { 1, 2, 3 } and porosities from [0.55 - 0.95]. We determined that a minimum of 6, 8 and 10 stochastic simulations, respec- tively, were required to calculate these average tortuosity values in laminar flow （Re 〈〈 1）. This novel application of the LBM to study the effects of porosity and aspect ratio of rectangular grains on tortuosity can be used in the tailoring of materials for clean energy.
