In the present study,the modified Sverjensky-Molling equation,derived from a linear-free energy relationship,is used to predict the Gibbs free energies of formation of crystalline phases ofα-MOOH （with a goethite st...In the present study,the modified Sverjensky-Molling equation,derived from a linear-free energy relationship,is used to predict the Gibbs free energies of formation of crystalline phases ofα-MOOH （with a goethite structure）andα-M_2O_3（with a hematite structure）from the known thermodynamic properties of the corresponding aqueous trivalent cations（M^（3＋））.The modified equation is expressed asΔG_（f,M_VX）~0=a_（M_VX）ΔG_（0,M^（3＋））^（0）＋b_（M_VX）＋β_（M_VXγM^（3＋））,where the coefficients a_（M_VX）,b_（M_VX）,andβ_（M_VX） characterize a particular structural family of M_VX（M is a trivalent cation[M^（3＋）]and X represents the remainder of the composition of solid）;γ^（3＋）is the ionic radius of trivalent cations（M^（3＋））;ΔG_（f,M_VX）~0 is the standard Gibbs free energy of formation of M_vX;andΔG_（n,M^（3＋））~0 is the non-solvation energy of trivalent cations（M^（3＋））.By fitting the equation to the known experimental thermodynamic data,the coefficients for the goethite family（α-MOOH）are a_（M_VX）=0.8838,b_（M_VX）=-424.4431（kcal/mol）,andβ_（M_VX）=115（kcal/ mol.（？））,while the coefficients for the hematite family（α-M_2O_3）are a_（M_VX）=1.7468,b_（M_VX）=-814.9573（kcal/ mol）,andβ_（M_VX）=278（kcal/mol.（？））.The constrained relationship can be used to predict the standard Gibbs free energies of formation of crystalline phases and fictive phases（i.e.phases that are thermodynamically unstable and do not occur at standard conditions）within the isostructural families of goethite（α-MOOH）and hematite（α-M_2O_3）if the standard Gibbs free energies of formation of the trivalent cations are known.展开更多
Elaborate interface engineering based on in situ surface reconstruction during catalysis,especially at the cathode,is effective at promoting the hydrogen evolution reaction(HER)but is plagued by the uncontrollable ext...Elaborate interface engineering based on in situ surface reconstruction during catalysis,especially at the cathode,is effective at promoting the hydrogen evolution reaction(HER)but is plagued by the uncontrollable extent of the reconstruction and structure collapse.In view of the reasonable adsorption of reaction intermediates and accelerating kinetics of hydroxy oxides(MOOH),we focused on the in situ structural evolution of the HER electrode toward MOOH during catalysis,which has been revealed by operando Raman spectroscopy yet seldom reported.As a typical example,Mn-doped NiS_(2)was selected as the HER electrode to monitor in situ structural evolution toward hydroxy oxides(cathode in situ-derived NiOOH,CISD-NiOOH)as Mn-NiS_(2)@CISD-NiOOH coupling catalysts.In situ formation of MOOH on the cathode is interesting.Moreover,the existence of Mn dopants renders Mn-NiS_(2)with lattice distortion and a rough surface consisting of nanoparticles of∼25 nm in diameter,differing from the smooth NiS_(2).In 1 M KOH,Mn-NiS_(2)@CISD-NiOOH exhibits a low overpotential of 330 mV to deliver 1000 mA cm^(−2)and an excellent stability of 100 h at 1300 mA cm^(−2).Notably,in alkaline seawater(1 M KOH+seawater)as well as 30%KOH industrial electrolyte,it still exhibits stable HER operation above 1000 mA cm^(−2)for at least 100 h.This study not only expands the prospects for in situ cathode structure development but also offers a robust catalytic cathode with high activity for industrial hydrogen-production systems.展开更多
基金supported by the NSFC(no 40473024 and 40343019)Project of the 11th and 10th Five-Year Research and Development of International Seabed(noDYXM-115-02-1-11,PY105-01-04-13 and DY 105-01-02-1)+2 种基金Project of Key Laboratory of Marginal Sea Geology,Guangzhou Institute of Geochemistry and South China Sea Institute of Oceanology,CAS(no MSGL08-01,MSGLCAS03-4)Specialized Research Fund for the Doctoral Program of Higher Education(no 20040558049)the Fundamental Research Funds for the Central Universities
文摘In the present study,the modified Sverjensky-Molling equation,derived from a linear-free energy relationship,is used to predict the Gibbs free energies of formation of crystalline phases ofα-MOOH （with a goethite structure）andα-M_2O_3（with a hematite structure）from the known thermodynamic properties of the corresponding aqueous trivalent cations（M^（3＋））.The modified equation is expressed asΔG_（f,M_VX）~0=a_（M_VX）ΔG_（0,M^（3＋））^（0）＋b_（M_VX）＋β_（M_VXγM^（3＋））,where the coefficients a_（M_VX）,b_（M_VX）,andβ_（M_VX） characterize a particular structural family of M_VX（M is a trivalent cation[M^（3＋）]and X represents the remainder of the composition of solid）;γ^（3＋）is the ionic radius of trivalent cations（M^（3＋））;ΔG_（f,M_VX）~0 is the standard Gibbs free energy of formation of M_vX;andΔG_（n,M^（3＋））~0 is the non-solvation energy of trivalent cations（M^（3＋））.By fitting the equation to the known experimental thermodynamic data,the coefficients for the goethite family（α-MOOH）are a_（M_VX）=0.8838,b_（M_VX）=-424.4431（kcal/mol）,andβ_（M_VX）=115（kcal/ mol.（？））,while the coefficients for the hematite family（α-M_2O_3）are a_（M_VX）=1.7468,b_（M_VX）=-814.9573（kcal/ mol）,andβ_（M_VX）=278（kcal/mol.（？））.The constrained relationship can be used to predict the standard Gibbs free energies of formation of crystalline phases and fictive phases（i.e.phases that are thermodynamically unstable and do not occur at standard conditions）within the isostructural families of goethite（α-MOOH）and hematite（α-M_2O_3）if the standard Gibbs free energies of formation of the trivalent cations are known.
基金the Natural Science Foundation of Shandong Province(ZR2020QB068)China Postdoctoal Science Foundation(2021M691701).
文摘Elaborate interface engineering based on in situ surface reconstruction during catalysis,especially at the cathode,is effective at promoting the hydrogen evolution reaction(HER)but is plagued by the uncontrollable extent of the reconstruction and structure collapse.In view of the reasonable adsorption of reaction intermediates and accelerating kinetics of hydroxy oxides(MOOH),we focused on the in situ structural evolution of the HER electrode toward MOOH during catalysis,which has been revealed by operando Raman spectroscopy yet seldom reported.As a typical example,Mn-doped NiS_(2)was selected as the HER electrode to monitor in situ structural evolution toward hydroxy oxides(cathode in situ-derived NiOOH,CISD-NiOOH)as Mn-NiS_(2)@CISD-NiOOH coupling catalysts.In situ formation of MOOH on the cathode is interesting.Moreover,the existence of Mn dopants renders Mn-NiS_(2)with lattice distortion and a rough surface consisting of nanoparticles of∼25 nm in diameter,differing from the smooth NiS_(2).In 1 M KOH,Mn-NiS_(2)@CISD-NiOOH exhibits a low overpotential of 330 mV to deliver 1000 mA cm^(−2)and an excellent stability of 100 h at 1300 mA cm^(−2).Notably,in alkaline seawater(1 M KOH+seawater)as well as 30%KOH industrial electrolyte,it still exhibits stable HER operation above 1000 mA cm^(−2)for at least 100 h.This study not only expands the prospects for in situ cathode structure development but also offers a robust catalytic cathode with high activity for industrial hydrogen-production systems.
