Water splitting has been regarded as a sustainable and environmentally-friendly technique to realize green hydrogen generation,while more energy is consumed due to the high overpotentials required for the anode oxygen...Water splitting has been regarded as a sustainable and environmentally-friendly technique to realize green hydrogen generation,while more energy is consumed due to the high overpotentials required for the anode oxygen evolution reaction.Urea electrooxidation,an ideal substitute,is thus received increasing attention in assisting water-splitting reactions.Note that highly efficient catalysts are still required to drive urea oxidation,and the facile generation of high valence state species is significant in the reaction based on the electrochemicalchemical mechanisms.The high cost and rareness make the noble metal catalysts impossible for further consideration in large-scale application.Ni-based catalysts are very promising due to their cheap price,facile structure tuning,good compatibility,and easy active phase formation.In the light of the significant advances made recently,herein,we reviewed the recent advances of Ni-based powder catalysts for urea oxidation in assisting water-splitting reaction.The fundamental of urea oxidation is firstly presented to clarify the mechanism of urea-assisted water splitting,and then the prevailing evaluation indicators are briefly expressed based on the electrochemical measurements.The catalyst design principle including synergistic effect,electronic effect,defect construction and surface reconstruction as well as the main fabrication approaches are presented and the advances of various Ni-based powder catalysts for urea assisted water splitting are summarized and discussed.The problems and challenges are also concluded for the Ni-based powder catalysts fabrication,the performance evaluation,and their application.Considering the key influencing factors for catalytic process and their application,attention should be given to structure-property relationship deciphering,novel Ni-based powder catalysts development and their construction in the real device;specifically,the effort should be directed to the Ni-based powder catalyst with multi-functions to simultaneously promote the fundamental steps and high anti-corrosion ability by revealing the local structure reconstruction as well as the integration in the practical application.We believe the current summarization will be instructive and helpful for the Ni-based powder catalysts development and understanding their catalytic action for urea-assisted hydrogen generation via water splitting technique.展开更多
In this study, Al_2O_3-washcoated SiC(Al_2O_3–SiC) foams and Al_2O_3 powder were employed as the supports of a Ni catalyst for the liquid-phase hydrogenation of benzaldehyde. A series of Ni/Al_2O_3–SiC foam catalyst...In this study, Al_2O_3-washcoated SiC(Al_2O_3–SiC) foams and Al_2O_3 powder were employed as the supports of a Ni catalyst for the liquid-phase hydrogenation of benzaldehyde. A series of Ni/Al_2O_3–SiC foam catalysts and Ni/Al_2O_3 powder catalysts with a Ni loading from 10 wt% to 37 wt% of the weight of Al_2O_3 were first prepared by a deposition–precipitation(DP) method. The catalytic activity and recyclability of both kinds of catalysts were then compared. Although it had a smaller accessible surface area with the reactant, the foam catalyst with a Ni loading of 16 wt% exhibited a slightly higher conversion of benzaldehyde after 6 h(of 99.3%) in comparison with the Ni/Al_2O_3 catalyst with identical Ni loading(conversion of 97.5%). When the Ni loading increased from 16 wt% to 37 wt%, the reaction rate obtained with the foam catalyst increased significantly from 0.108 to 0.204 mol L^(-1)h^(-1), whereas the reaction rate obtained with the powder catalyst increased from 0.106 to 0.123 mol L^(-1)h^(-1). Furthermore, the specific activity(moles of benzaldehyde consumed by 1 g min^(-1)of Ni) of the foam catalyst with a Ni loading above 30 wt% was superior to that of the powder catalyst because of its smaller Ni-particle size and higher mass-transfer rate. The foam catalyst displayed a high recyclability as a function of run times owing to the strong interaction between the Ni component and the Al_2O_3 coating. The conversion of benzaldehyde over the foam catalyst remained almost unchanged after being used 8 times. In comparison, a drop of 43% in the conversion of benzaldehyde with the powder catalyst was observed after being used 7 times due to the leaching of the Ni component.展开更多
An extensive study has been conducted on the proton exchange membrane fuel cells （PEMFCs） with reducing Pt loading. This is commonly achieved by developing methods to increase the utilization of the platinum in the ...An extensive study has been conducted on the proton exchange membrane fuel cells （PEMFCs） with reducing Pt loading. This is commonly achieved by developing methods to increase the utilization of the platinum in the catalyst layer of the electrodes. In this paper, a novel process of the catalyst layers was introduced and investigated. A mixture of carbon powder and Nafion solution was sprayed on the glassy carbon electrode （GCE） to form a thin carbon layer. Then Pt particles were deposited on the surface by reducing hexachloroplatinic （IV） acid hexahydrate with methanoic acid. SEM images showed a continuous Pt gradient profile among the thickness direction of the catalytic layer by the novel method. The Pt nanowires grown are in the size of 3 nm （diameter） x l0 nm （length） by high solution TEM image. The novel catalyst layer was characterized by cyclic voltammetry （CV） and scanning electron microscope （SEM） as compared with commercial Pt/C black and Pt catalyst layer obtained from sputtering. The results showed that the platinum nanoparticles deposited on the carbon powder were highly utilized as they directly faced the gas diffusion layer and offered easy access to reactants （oxygen or hydrogen）.展开更多
In this paper, diamond crystallization from carbonyl nickel powders-C and carbonyl nickel powders + Fe–C systems are investigated in detail at a pressure of 6.0 GPa and temperatures ranging from 1410°C–to 1435&...In this paper, diamond crystallization from carbonyl nickel powders-C and carbonyl nickel powders + Fe–C systems are investigated in detail at a pressure of 6.0 GPa and temperatures ranging from 1410°C–to 1435°C by temperature gradient growth. The effects of Fe additive on the crystal morphology are discussed in the diamond crystallization process.Furthermore, Fourier infrared measurement results indicate that the spectrum of the diamond obtained from Ni + Fe–C system after annealing treatment is nearly consistent with that of natural diamond crystal. We believe that this study is of benefit to a further understanding of the growth mechanism of natural diamond.展开更多
基金supported by the National Natural Science Foundation of China(Grant Nos.22102105,21972124)the Priority Academic Program Development of Jiangsu Higher Education Institution.The author Ligang Feng also appreciates the support of the Six Talent Peaks Project of Jiangsu Province,China(No.XCL-070-2018).
文摘Water splitting has been regarded as a sustainable and environmentally-friendly technique to realize green hydrogen generation,while more energy is consumed due to the high overpotentials required for the anode oxygen evolution reaction.Urea electrooxidation,an ideal substitute,is thus received increasing attention in assisting water-splitting reactions.Note that highly efficient catalysts are still required to drive urea oxidation,and the facile generation of high valence state species is significant in the reaction based on the electrochemicalchemical mechanisms.The high cost and rareness make the noble metal catalysts impossible for further consideration in large-scale application.Ni-based catalysts are very promising due to their cheap price,facile structure tuning,good compatibility,and easy active phase formation.In the light of the significant advances made recently,herein,we reviewed the recent advances of Ni-based powder catalysts for urea oxidation in assisting water-splitting reaction.The fundamental of urea oxidation is firstly presented to clarify the mechanism of urea-assisted water splitting,and then the prevailing evaluation indicators are briefly expressed based on the electrochemical measurements.The catalyst design principle including synergistic effect,electronic effect,defect construction and surface reconstruction as well as the main fabrication approaches are presented and the advances of various Ni-based powder catalysts for urea assisted water splitting are summarized and discussed.The problems and challenges are also concluded for the Ni-based powder catalysts fabrication,the performance evaluation,and their application.Considering the key influencing factors for catalytic process and their application,attention should be given to structure-property relationship deciphering,novel Ni-based powder catalysts development and their construction in the real device;specifically,the effort should be directed to the Ni-based powder catalyst with multi-functions to simultaneously promote the fundamental steps and high anti-corrosion ability by revealing the local structure reconstruction as well as the integration in the practical application.We believe the current summarization will be instructive and helpful for the Ni-based powder catalysts development and understanding their catalytic action for urea-assisted hydrogen generation via water splitting technique.
基金the financial support of the project from the National Key Research&Development Program of China(No.2017YFB0310405)
文摘In this study, Al_2O_3-washcoated SiC(Al_2O_3–SiC) foams and Al_2O_3 powder were employed as the supports of a Ni catalyst for the liquid-phase hydrogenation of benzaldehyde. A series of Ni/Al_2O_3–SiC foam catalysts and Ni/Al_2O_3 powder catalysts with a Ni loading from 10 wt% to 37 wt% of the weight of Al_2O_3 were first prepared by a deposition–precipitation(DP) method. The catalytic activity and recyclability of both kinds of catalysts were then compared. Although it had a smaller accessible surface area with the reactant, the foam catalyst with a Ni loading of 16 wt% exhibited a slightly higher conversion of benzaldehyde after 6 h(of 99.3%) in comparison with the Ni/Al_2O_3 catalyst with identical Ni loading(conversion of 97.5%). When the Ni loading increased from 16 wt% to 37 wt%, the reaction rate obtained with the foam catalyst increased significantly from 0.108 to 0.204 mol L^(-1)h^(-1), whereas the reaction rate obtained with the powder catalyst increased from 0.106 to 0.123 mol L^(-1)h^(-1). Furthermore, the specific activity(moles of benzaldehyde consumed by 1 g min^(-1)of Ni) of the foam catalyst with a Ni loading above 30 wt% was superior to that of the powder catalyst because of its smaller Ni-particle size and higher mass-transfer rate. The foam catalyst displayed a high recyclability as a function of run times owing to the strong interaction between the Ni component and the Al_2O_3 coating. The conversion of benzaldehyde over the foam catalyst remained almost unchanged after being used 8 times. In comparison, a drop of 43% in the conversion of benzaldehyde with the powder catalyst was observed after being used 7 times due to the leaching of the Ni component.
基金supported by the Royal Academy of Engineering,United Kingdom
文摘An extensive study has been conducted on the proton exchange membrane fuel cells （PEMFCs） with reducing Pt loading. This is commonly achieved by developing methods to increase the utilization of the platinum in the catalyst layer of the electrodes. In this paper, a novel process of the catalyst layers was introduced and investigated. A mixture of carbon powder and Nafion solution was sprayed on the glassy carbon electrode （GCE） to form a thin carbon layer. Then Pt particles were deposited on the surface by reducing hexachloroplatinic （IV） acid hexahydrate with methanoic acid. SEM images showed a continuous Pt gradient profile among the thickness direction of the catalytic layer by the novel method. The Pt nanowires grown are in the size of 3 nm （diameter） x l0 nm （length） by high solution TEM image. The novel catalyst layer was characterized by cyclic voltammetry （CV） and scanning electron microscope （SEM） as compared with commercial Pt/C black and Pt catalyst layer obtained from sputtering. The results showed that the platinum nanoparticles deposited on the carbon powder were highly utilized as they directly faced the gas diffusion layer and offered easy access to reactants （oxygen or hydrogen）.
基金supported by the National Natural Science Foundation of China(Grant No.51172089)the Natural Science Foundation of Guizhou Provincial Education Department,China(Grant No.KY[2013]183)the Research Fund for the Doctoral Program of Tongren University,China(Grant Nos.DS1302 and trxy S1415)
文摘In this paper, diamond crystallization from carbonyl nickel powders-C and carbonyl nickel powders + Fe–C systems are investigated in detail at a pressure of 6.0 GPa and temperatures ranging from 1410°C–to 1435°C by temperature gradient growth. The effects of Fe additive on the crystal morphology are discussed in the diamond crystallization process.Furthermore, Fourier infrared measurement results indicate that the spectrum of the diamond obtained from Ni + Fe–C system after annealing treatment is nearly consistent with that of natural diamond crystal. We believe that this study is of benefit to a further understanding of the growth mechanism of natural diamond.
