Recently,carbon-based metal-free electrocatalysts(C‐MFECs)have drawn considerable research attention because of their attractive physicochemical characteristics,cost-effectiveness,and ability to convert and store ene...Recently,carbon-based metal-free electrocatalysts(C‐MFECs)have drawn considerable research attention because of their attractive physicochemical characteristics,cost-effectiveness,and ability to convert and store energy efficiently.Efficient intramolecular charge transfer among different parts of the carbon electrocatalyst and/or intermolecular charge transfer between elec-trocatalyst and electrolyte dictate the ultimate energy conversion performance.Experimental results and theoretical analyses have demonstrated that rational design of metal-free carbon nanomaterials,coupled with proper in-tramolecular charge transfer through heteroatom doping,incorporation of Stone-Wales defects,and/or intermolecular charge transfer through adsorp-tion of appropriate molecules/moieties,can promote efficient electrocatalysis.In this article,we will first provide the related theoretical principles and then present an overview on the rational design and development of C-MFECs for efficient charge transfer,followed by elucidating charge-transfer processes for different electrocatalytic reactions related to renewable energy conversion and environmental remediation technologies.Finally,the current challenges and future perspectives in this exciting field will be discussed.展开更多
The lattice Boltzmann Peierls Callaway(LBPC)method is a recent development of the versatile lattice Boltzmann formalism aimed at a numerical experiment on mesoscale thermal transport in a multiphase phonon gas.Two asp...The lattice Boltzmann Peierls Callaway(LBPC)method is a recent development of the versatile lattice Boltzmann formalism aimed at a numerical experiment on mesoscale thermal transport in a multiphase phonon gas.Two aspects of mesoscopic thermal trans-port are discussed:the finite phonon mean free path and the interface thermal resistance.Based on the phonon momentum screening length measured in the LBPC computa-tional apparatus,the validity of the Umklapp collision relaxation time in the Callaway collision operator is examined quantitatively.The discrete nature of the spatio-temporal domain in the LBPC method,along with the linear approximation of the exponential screening mechanism in the Callaway operator,reveals a large discrepancy between the effective phonon mean free path and the analytic phonon mean free path when the relaxation time is small.The link bounce back interface phonon collision rule is used to realize the interface thermal resistance between phonon gases with dissimilar dispersion relations.Consistent with the Callaway collision operator for the bulk phonon dynam-ics,the interface phonon collision process is regarded as a linear relaxation mechanism toward the local pseudo-equilibrium phonon distribution uniquely defined by the energy conservation principle.The interface thermal resistance is linearly proportional to the relaxation time of the proposed phonon interface collision rule.展开更多
基金RP would like to thank Air Force Research Laboratory(AFRL)for providing financial support(Grant:165852.02.00.0001.00.06-C2 under prime contract FA8650-16-D-5852)LD is grateful to Australian Re-search Council(ARC,DP 190103881 and FL 190100126)for partial support.
文摘Recently,carbon-based metal-free electrocatalysts(C‐MFECs)have drawn considerable research attention because of their attractive physicochemical characteristics,cost-effectiveness,and ability to convert and store energy efficiently.Efficient intramolecular charge transfer among different parts of the carbon electrocatalyst and/or intermolecular charge transfer between elec-trocatalyst and electrolyte dictate the ultimate energy conversion performance.Experimental results and theoretical analyses have demonstrated that rational design of metal-free carbon nanomaterials,coupled with proper in-tramolecular charge transfer through heteroatom doping,incorporation of Stone-Wales defects,and/or intermolecular charge transfer through adsorp-tion of appropriate molecules/moieties,can promote efficient electrocatalysis.In this article,we will first provide the related theoretical principles and then present an overview on the rational design and development of C-MFECs for efficient charge transfer,followed by elucidating charge-transfer processes for different electrocatalytic reactions related to renewable energy conversion and environmental remediation technologies.Finally,the current challenges and future perspectives in this exciting field will be discussed.
文摘The lattice Boltzmann Peierls Callaway(LBPC)method is a recent development of the versatile lattice Boltzmann formalism aimed at a numerical experiment on mesoscale thermal transport in a multiphase phonon gas.Two aspects of mesoscopic thermal trans-port are discussed:the finite phonon mean free path and the interface thermal resistance.Based on the phonon momentum screening length measured in the LBPC computa-tional apparatus,the validity of the Umklapp collision relaxation time in the Callaway collision operator is examined quantitatively.The discrete nature of the spatio-temporal domain in the LBPC method,along with the linear approximation of the exponential screening mechanism in the Callaway operator,reveals a large discrepancy between the effective phonon mean free path and the analytic phonon mean free path when the relaxation time is small.The link bounce back interface phonon collision rule is used to realize the interface thermal resistance between phonon gases with dissimilar dispersion relations.Consistent with the Callaway collision operator for the bulk phonon dynam-ics,the interface phonon collision process is regarded as a linear relaxation mechanism toward the local pseudo-equilibrium phonon distribution uniquely defined by the energy conservation principle.The interface thermal resistance is linearly proportional to the relaxation time of the proposed phonon interface collision rule.
