Hydrogen has been regarded as a promising renewable and green energy source to meet energy needs and attain net-zero carbon emissions.The electrolysis of seawater to make hydrogen is one of the fascinating development...Hydrogen has been regarded as a promising renewable and green energy source to meet energy needs and attain net-zero carbon emissions.The electrolysis of seawater to make hydrogen is one of the fascinating developments of the twenty-first century.This method uses abundant and relatively inexpensive seawater,as opposed to freshwater,which is rare and can be prohibitively expensive.In recent years,significant research and advancements have been made in direct seawater electrolysis technology for hydrogen production.However,producing highly effective and efficient electrocatalysts with long-term viability under harsh corrosive conditions remains a challenging and severe topic for large-scale seawater electrolysis technology.There is still a large accomplishment gap in understanding how to improve seawater electrolysis to increase hydrogen yields and prolong stability.It is,therefore,crucial to have a condensed knowledge of the tunable and inherent interactions between various electrocatalysts,covering electrolyzer types and paying particular attention to those with high efficiency,chemical stability,and conductivity.The extensive discussion is structured into a progression from noble metals to base metal compounds such as oxides,alloys,phosphides,chalcogenides,hydroxides,and nitrides,MXene-based complexes with a concise examination of hybrid electrocatalysts.In addition,proton exchange membranes,anion exchange membranes,alkaline water electrolyzers,and high-temperature water electrolyzers were potential contributors to seawater’s electrolysis.An extensive assessment of the techno-feasibility,economic insights,and future suggestions was done to commercialize the most efficient electrocatalytic systems for hydrogen production.This review is anticipated to provide academics,environmentalists,and industrial researchers with valuable ideas for constructing and modifying seawater-based electrocatalysts.展开更多
The continued increase in population and the industrial revolution have led to an increase in atmospheric carbon dioxide(CO_(2)) concentration. Consequently, developing and implementing effective solutions to reduce C...The continued increase in population and the industrial revolution have led to an increase in atmospheric carbon dioxide(CO_(2)) concentration. Consequently, developing and implementing effective solutions to reduce CO_(2) emissions is a global priority. The electrochemical CO_(2) reduction reaction(CO_(2)RR) is strongly believed to be a promising alternative to fossil fuel-based technologies for the production of value-added chemicals. So far, the implementation of CO_(2)RR is hindered by associated electrochemical reactions, such as low selectivity, hydrogen evolution reaction(HER), and additional overpotential induced in some cases. As a result, it is necessary to conduct a timely evaluation of the state-of-the-art strategies in CO_(2)RR, with a focus on the engineering of the electrocatalytic systems. Catalyst morphology is one factor that plays a critical role in overcoming these drawbacks and significantly contributes to enhancing product selectivity and Faradaic efficiency(FE). This review article summarizes the recent advances in the rational design of electrocatalysts with various morphologies and the influence of these morphologies on CO_(2)RR. To compare literature findings in a meaningful way, the article focuses on results reported under a well-defined period and considers the first three rows of the d-block metal catalysts. The discussion typically covers the design of nanostructured catalysts and the molecular-level understanding of morphology-performance relationship in terms of activity, selectivity, and stability during CO_(2) electrolysis. Among others, it would be convenient to recommend a comprehensive discussion on the morphologies of single metals and heterostructures, with a detailed emphasis on their impact on CO_(2) conversion.展开更多
Ethane,one of the key components of shale gas,is a valuable feedstock for the production of syngas(CO+H_(2))via the C-C bond cleavage during dry reforming of ethane(DRE)reaction.Selective catalysts are needed to direc...Ethane,one of the key components of shale gas,is a valuable feedstock for the production of syngas(CO+H_(2))via the C-C bond cleavage during dry reforming of ethane(DRE)reaction.Selective catalysts are needed to direct this reaction pathway against the competing C-H bond cleavage for ethylene formation.In this study,Fe,V and Rh oxides supported on TiO_(2)catalysts were prepared by impregnation method.The catalysts were tested for DRE with the main target of enhancing selectivity to syngas(CO and H_(2))and reducing byproducts(methane and ethylene)formation.The catalysts were characterized using X-ray diffraction,scanning electron microscopy,NH_(3)/CO_(2)temperature programmed desorption and H_(2)-temperature programmed reduction.Temperature programmed oxidation was utilized to characterize the coke contents of the spent catalysts.The catalysts were evaluated for DRE reaction in a fixed-bed reactor at the temperature range from 500℃to 650℃and CO_(2)/ethane ratio from 2:1 to 10:1(mol/mol).It was found that ethane conversion over the three catalysts increased in the order Rh/TiO_(2)>Fe/TiO_(2)>V/TiO_(2).Rh/TiO_(2)catalyst exhibited>99%ethane conversion,36%and 61%yields of H_(2)and CO,respectively,at 650℃and CO_(2)/ethane ratio of 5.0.The high conversion of ethane was mainly attributed to the enhanced dispersion of Rh oxides on the TiO_(2)support coupled with the balanced surface acidic and basic sites.The Rh catalyst facilitated C-C bond dissociation of ethane thereby forming methyl intermediates which then reacted with adsorbed CO_(2),thereby enhancing higher syngas production during DRE reaction.展开更多
In this study,a turbulent non-premixed(diffusion)methane-air flame has been investigated computationally to analyze the influences of pressure and gravity on flame structure and sooting characteristics between 1 and 1...In this study,a turbulent non-premixed(diffusion)methane-air flame has been investigated computationally to analyze the influences of pressure and gravity on flame structure and sooting characteristics between 1 and 10 atm.The simulation has been conducted in a 2-D axisymmetric computational domain using the finite volume-based computational fluid dynamics(CFD)code.The interaction of turbulence and chemistry is modeled by considering the steady laminar flamelet model(SLFM)and the GRI Mech 3.0 chemical mechanism.The radiative heat transfer calculation is carried out by considering the discrete ordinate(DO)method and the weighted sum grey gas model(WSGGM).The semi-empirical Moss-Brookes model is considered to calculate soot.The impact of gravity on flame and sooting characteristics are evaluated by comparing the normal-gravity flames with the zero-gravity flames.The effect of soot and radiation on flame temperature is also examined.The results show a close agreement with the measurement when both soot and radiation are included in the numerical modeling.The rates of soot formation,surface growth,and oxidation increase with increased operating pressure,regardless of gravity.Zero-gravity flames have a higher soot volume fraction,a wider soot-containing zone,a higher CO mass fraction,and a lower flame temperature than normal-gravity flames while maintaining constant pressure.In normal-gravity flames,the CO mass fraction decreases with pressure,whereas it increases with pressure rise in flames of zero gravity.Flames of zero gravity appear taller and broader compared to the flames of normalgravity for a fixed pressure.An increase in pressure significantly reduces the flame length and width in normal-gravity flames.However,the pressure elevation has little effect on the shape of a zero-gravity flame.The outcomes of the present study will assist in fully understanding the combustion and sooting characteristics of turbulent diffusion flames that will help design and develop high-efficiency,pollutant-free combustion devices and fire suppression systems for space application.展开更多
基金the support provided by the Deanship of Scientific Research at Majmaah University,P.O.Box 66,Majmaah 11952,Saudi Arabia under Project No.R-2023-6Center for Refining and Advanced Chemicals,Research Institute,King Fahd University of Petroleum and Minerals(KFUPM),Saudi Arabia。
文摘Hydrogen has been regarded as a promising renewable and green energy source to meet energy needs and attain net-zero carbon emissions.The electrolysis of seawater to make hydrogen is one of the fascinating developments of the twenty-first century.This method uses abundant and relatively inexpensive seawater,as opposed to freshwater,which is rare and can be prohibitively expensive.In recent years,significant research and advancements have been made in direct seawater electrolysis technology for hydrogen production.However,producing highly effective and efficient electrocatalysts with long-term viability under harsh corrosive conditions remains a challenging and severe topic for large-scale seawater electrolysis technology.There is still a large accomplishment gap in understanding how to improve seawater electrolysis to increase hydrogen yields and prolong stability.It is,therefore,crucial to have a condensed knowledge of the tunable and inherent interactions between various electrocatalysts,covering electrolyzer types and paying particular attention to those with high efficiency,chemical stability,and conductivity.The extensive discussion is structured into a progression from noble metals to base metal compounds such as oxides,alloys,phosphides,chalcogenides,hydroxides,and nitrides,MXene-based complexes with a concise examination of hybrid electrocatalysts.In addition,proton exchange membranes,anion exchange membranes,alkaline water electrolyzers,and high-temperature water electrolyzers were potential contributors to seawater’s electrolysis.An extensive assessment of the techno-feasibility,economic insights,and future suggestions was done to commercialize the most efficient electrocatalytic systems for hydrogen production.This review is anticipated to provide academics,environmentalists,and industrial researchers with valuable ideas for constructing and modifying seawater-based electrocatalysts.
文摘The continued increase in population and the industrial revolution have led to an increase in atmospheric carbon dioxide(CO_(2)) concentration. Consequently, developing and implementing effective solutions to reduce CO_(2) emissions is a global priority. The electrochemical CO_(2) reduction reaction(CO_(2)RR) is strongly believed to be a promising alternative to fossil fuel-based technologies for the production of value-added chemicals. So far, the implementation of CO_(2)RR is hindered by associated electrochemical reactions, such as low selectivity, hydrogen evolution reaction(HER), and additional overpotential induced in some cases. As a result, it is necessary to conduct a timely evaluation of the state-of-the-art strategies in CO_(2)RR, with a focus on the engineering of the electrocatalytic systems. Catalyst morphology is one factor that plays a critical role in overcoming these drawbacks and significantly contributes to enhancing product selectivity and Faradaic efficiency(FE). This review article summarizes the recent advances in the rational design of electrocatalysts with various morphologies and the influence of these morphologies on CO_(2)RR. To compare literature findings in a meaningful way, the article focuses on results reported under a well-defined period and considers the first three rows of the d-block metal catalysts. The discussion typically covers the design of nanostructured catalysts and the molecular-level understanding of morphology-performance relationship in terms of activity, selectivity, and stability during CO_(2) electrolysis. Among others, it would be convenient to recommend a comprehensive discussion on the morphologies of single metals and heterostructures, with a detailed emphasis on their impact on CO_(2) conversion.
文摘Ethane,one of the key components of shale gas,is a valuable feedstock for the production of syngas(CO+H_(2))via the C-C bond cleavage during dry reforming of ethane(DRE)reaction.Selective catalysts are needed to direct this reaction pathway against the competing C-H bond cleavage for ethylene formation.In this study,Fe,V and Rh oxides supported on TiO_(2)catalysts were prepared by impregnation method.The catalysts were tested for DRE with the main target of enhancing selectivity to syngas(CO and H_(2))and reducing byproducts(methane and ethylene)formation.The catalysts were characterized using X-ray diffraction,scanning electron microscopy,NH_(3)/CO_(2)temperature programmed desorption and H_(2)-temperature programmed reduction.Temperature programmed oxidation was utilized to characterize the coke contents of the spent catalysts.The catalysts were evaluated for DRE reaction in a fixed-bed reactor at the temperature range from 500℃to 650℃and CO_(2)/ethane ratio from 2:1 to 10:1(mol/mol).It was found that ethane conversion over the three catalysts increased in the order Rh/TiO_(2)>Fe/TiO_(2)>V/TiO_(2).Rh/TiO_(2)catalyst exhibited>99%ethane conversion,36%and 61%yields of H_(2)and CO,respectively,at 650℃and CO_(2)/ethane ratio of 5.0.The high conversion of ethane was mainly attributed to the enhanced dispersion of Rh oxides on the TiO_(2)support coupled with the balanced surface acidic and basic sites.The Rh catalyst facilitated C-C bond dissociation of ethane thereby forming methyl intermediates which then reacted with adsorbed CO_(2),thereby enhancing higher syngas production during DRE reaction.
基金Authors(SG,VMR,SKD)would like to acknowledge the support received from the Institute seed grant(ISIRD)project(KNH).
文摘In this study,a turbulent non-premixed(diffusion)methane-air flame has been investigated computationally to analyze the influences of pressure and gravity on flame structure and sooting characteristics between 1 and 10 atm.The simulation has been conducted in a 2-D axisymmetric computational domain using the finite volume-based computational fluid dynamics(CFD)code.The interaction of turbulence and chemistry is modeled by considering the steady laminar flamelet model(SLFM)and the GRI Mech 3.0 chemical mechanism.The radiative heat transfer calculation is carried out by considering the discrete ordinate(DO)method and the weighted sum grey gas model(WSGGM).The semi-empirical Moss-Brookes model is considered to calculate soot.The impact of gravity on flame and sooting characteristics are evaluated by comparing the normal-gravity flames with the zero-gravity flames.The effect of soot and radiation on flame temperature is also examined.The results show a close agreement with the measurement when both soot and radiation are included in the numerical modeling.The rates of soot formation,surface growth,and oxidation increase with increased operating pressure,regardless of gravity.Zero-gravity flames have a higher soot volume fraction,a wider soot-containing zone,a higher CO mass fraction,and a lower flame temperature than normal-gravity flames while maintaining constant pressure.In normal-gravity flames,the CO mass fraction decreases with pressure,whereas it increases with pressure rise in flames of zero gravity.Flames of zero gravity appear taller and broader compared to the flames of normalgravity for a fixed pressure.An increase in pressure significantly reduces the flame length and width in normal-gravity flames.However,the pressure elevation has little effect on the shape of a zero-gravity flame.The outcomes of the present study will assist in fully understanding the combustion and sooting characteristics of turbulent diffusion flames that will help design and develop high-efficiency,pollutant-free combustion devices and fire suppression systems for space application.
