As a versatile and environmentally benign oxidant,hydrogen peroxide(H_(2)O_(2))is highly desired in sanitation,disinfection,environmental remediation,and the chemical industry.Compared with the conventional anthraquin...As a versatile and environmentally benign oxidant,hydrogen peroxide(H_(2)O_(2))is highly desired in sanitation,disinfection,environmental remediation,and the chemical industry.Compared with the conventional anthraquinone process,the electrosynthesis of H_(2)O_(2)through the two-electron oxygen reduction reaction(2e^(−)ORR)is an efficient,competitive,and promising avenue.Electrocatalysts and devices are two core factors in 2e^(−)ORR,but the design principles of catalysts for different pH conditions and the development trends of relevant synthesis devices remain unclear.To this end,this review adopts a multiscale perspective to summarize recent advancements in the design principles,catalytic mechanisms,and application prospects of 2e^(−)ORR catalysts,with a particular focus on the influence of pH conditions,aiming at providing guidance for the selective design of advanced 2e^(−)ORR catalysts for highly-efficient H_(2)O_(2)production.Moreover,in response to diverse on-site application demands,we elaborate on the evolution of H_(2)O_(2)electrosynthesis devices,from rotating ring-disk electrodes and H-type cells to diverse flow-type cells.We elaborate on their characteristics and shortcomings,which can be beneficial for their further upgrades and customized applications.These insights may inspire the rational design of innovative catalysts and devices with high performance and wide serviceability for large-scale implementations.展开更多
The hydrogen peroxide oxidation reaction (HPOOR) on Au(111) electrode in alkaline solutions with pH values ranging from 10 to 13 was examined systematically. HPOOR activity increased and the slope of the i-E curve dec...The hydrogen peroxide oxidation reaction (HPOOR) on Au(111) electrode in alkaline solutions with pH values ranging from 10 to 13 was examined systematically. HPOOR activity increased and the slope of the i-E curve decreased with increasing pH. HO2- is suggested to be the main reactive intermediate for HPOOR in alkaline media. The fast kinetics for HPOOR in alkaline solution is facilitated by the electrostatic interaction between the positively charged electrode and the reactive anions (i.e., HO2- and HO-), which increases the concentration of these reactants and the thermodynamic driving force for HO2- oxidation at the reaction plane.展开更多
The adsorption/desorption of OH*on electrode surfaces is pivotal in numerous electrocatalytic reactions.To understand the effect of electrolyte pH on that process,in this work,an advanced approach combining ab initio ...The adsorption/desorption of OH*on electrode surfaces is pivotal in numerous electrocatalytic reactions.To understand the effect of electrolyte pH on that process,in this work,an advanced approach combining ab initio molecular dynamics(AIMD)with free energy perturbation is employed to calculate the dehydrogenation free energy of water chemisorbed at differently electrified Pt(111)/electrolyte interfaces.Our findings reveal that the onset potential for OH*formation shifts negatively as the pH increases at low pH condition(pH<4.3),aligning with the cyclic voltammetry curves observed in experimental studies.It indicates the dissociation of chemisorbed water is the primary route for OH*adsorption at low pH condition.Furthermore,it is also found that the variation in dehydrogenation energy across different pH is primarily due to the local hydrogen bonding network surrounding the chemisorbed water.In addition,it is proposed that at high pH conditions OH-oxidation emerges as the primary route for OH*adsorption on Pt(111)constrained by the water chemisorption process.This work provides crucial insights into the pH-dependent adsorption behavior of OH*on the Pt(111)surface and aims to guide the optimization of electrolytes to boost the efficiency of related reactions.展开更多
Phosphoric acid/phosphate solu-tions are commonly used as buffer solutions in the fundamental stud-ies in electrochemistry.Informa-tion on the nature of adsorbed(bi)phosphate as well as the do-main structures is of gr...Phosphoric acid/phosphate solu-tions are commonly used as buffer solutions in the fundamental stud-ies in electrochemistry.Informa-tion on the nature of adsorbed(bi)phosphate as well as the do-main structures is of great impor-tance in unveiling the impact on electrochemical processes occur-ring at electrode electrolyte interface.In this work,the pH effect on the adsorption of phosphate related species on Pd(111)electrode has been investigated by cyclic voltammetry over a broad pH range from 1 to 14.Af-ter carefully analyzing the related onset desorption potential of(bi)phosphate adsorbate to the thermodynamic equilibrium potential of the corresponding electrode reactions,three dif-ferent phosphate related adsorbates have been identified,which are highly pH-dependent.Our analysis reveals that the dominant phosphate anions in bulk solution undergo deprotona-tion upon adsorption.At pH<1.5,the main adsorbate on Pd(111)is;H_(2)PO_(4)^(λ_(1)^(-))in solutions with 1.5<pH<7,the main adsorbate changes into.HPO_(4)^(λ_2^(-))At higher pHs,PO_(4)^(λ_(3)^(-))on electrode surface dominates.The exact charging value ofλ_(i),which represents the true va-lence of the(bi)phosphate adsorbate,could be determined using theoretical calculations.In addition,our results can not rule out the possibility of co-adsorbed H_(3)PO_(4)molecules on Pd(111)at pH<1.5,which needs to be proved by infrared spectroscopy in the future.展开更多
This study investigated the effects of pH on the transport of Pb 2＋ , Mn 2＋ , Zn 2＋ and Ni 2＋ through lateritic soil columns. Model results by fitting the symmetric breakthrough curves （BTCs） of bromide （Br ） ...This study investigated the effects of pH on the transport of Pb 2＋ , Mn 2＋ , Zn 2＋ and Ni 2＋ through lateritic soil columns. Model results by fitting the symmetric breakthrough curves （BTCs） of bromide （Br ） with CXTFIT model suggested that physical non-equilibrium processes were absent in the columns. The heavy metal BTCs were, however, asymmetrical and exhibited a tailing phenomenon, indicating the presence of chemical non-equilibrium processes in the columns. The retardation factors of Pb 2＋ were the largest of the four metal ions at both pH 4.0 （33.3） and pH 5.0 （35.4）. The use of Langmuir isotherm parameters from batch studies with HYDRUS-1D did not predict the BTCs well. Rather the two-site model （TSM） described the heavy metal BTCs better than the equilibrium linear/nonlinear Langmuir model. The fraction of instantaneous sorption sites （ f ） of all four metal ions on the lateritic soil was consistently about 30%–44% of the total sorption sites.展开更多
The Co-based catalysts were prepared with different cobalt acetate solutions.Effects of pH value were studied deeply on Fischer–Tropsch synthesis(FTS)through a semi-batch reactor.Among all impregnation solutions(wate...The Co-based catalysts were prepared with different cobalt acetate solutions.Effects of pH value were studied deeply on Fischer–Tropsch synthesis(FTS)through a semi-batch reactor.Among all impregnation solutions(water,butanol,amyl alcohol,acetic acid,nitric acid and ammonium nitrate),the catalyst prepared by NH4NO3solution showed the highest catalytic activity due to its small particle size and high reduction degree.However,the catalyst with the smallest particle size derived from water as impregnation solution exhibited low activity as well as high methane selectivity since it was difficult to be reduced and inactive in FTS.According to FT-IR spectra results,the low intensity of absorbed CO on the catalyst prepared from water solution resulted in low FTS activity.Whereas,the high activity of catalysts prepared from NH4NO3solution could be explained by the high intensity of absorbed CO on the catalysts.The cobalt species on the catalysts prepared under lower pH conditions exhibited smaller particle size distribution as well as lower CO conversion than those prepared at higher pH value.展开更多
In this study,we systematically investigated the effect of proton concentration on the kinetics of the oxygen reduction reaction(ORR)on Pt(111)in acidic solutions.Experimental results demonstrate a rectangular hyperbo...In this study,we systematically investigated the effect of proton concentration on the kinetics of the oxygen reduction reaction(ORR)on Pt(111)in acidic solutions.Experimental results demonstrate a rectangular hyperbolic relationship,i.e.,the ORR current excluding the effect of other variables increases with proton concentration and then tends to a constant value.We consider that this is caused by the limitation of ORR kinetics by the trace oxygen concentration in the solution,which determines the upper limit of ORR kinetics.A model of effective concentration is further proposed for rectangular hyperbolic relationships:when the reactant concentration is high enough to reach a critical saturation concentration,the effective reactant concentration will become a constant value.This could be due to the limited concentration of a certain reactant for reactions involving more than one reactant or the limited number of active sites available on the catalyst.Our study provides new insights into the kinetics of electrocatalytic reactions,and it is important for the proper evaluation of catalyst activity and the study of structureperformance relationships.展开更多
The oxygen reduction kinetics on polycobaltprotoporphyrin(PCoPP)film has been examined with the rotating disc electrode technique in O_2-saturated solution of various pH.PCoPP film promotes the oxygen reduction proces...The oxygen reduction kinetics on polycobaltprotoporphyrin(PCoPP)film has been examined with the rotating disc electrode technique in O_2-saturated solution of various pH.PCoPP film promotes the oxygen reduction process via two electrons to produce peroxide over wide pH range. When pH value of solution decreases,catalytic activity of PCoPP film increases.Possible catalytic mechanisms have been proposed for oxygen reduction.展开更多
STUDIES of radiation chemistry on methionine (Met) were very active in previous years because of its actions of radioprotection to biological systems by quenching·OH radicals. On the other hand, people have paid ...STUDIES of radiation chemistry on methionine (Met) were very active in previous years because of its actions of radioprotection to biological systems by quenching·OH radicals. On the other hand, people have paid more and more attention to the researches on the phosphorylation of the biological polymolecules. It is wall known that phosphate ester is regarded as the deposi-展开更多
In the present study the adsorptive properties of p-aminobenzoic acid with hypercrosslinked and multi-functional polymeric adsorbents at different solution pHs were systematically investigated in accordance with the p...In the present study the adsorptive properties of p-aminobenzoic acid with hypercrosslinked and multi-functional polymeric adsorbents at different solution pHs were systematically investigated in accordance with the particular physicochemical characteristics of the aromatic amphoteric compound involving both Lewis acid and Lewis base functional groups. It was found that the equilibrium adsorption data of the three polymeric adsorbents fitted well in the Langmuir and Freundlich isotherm equations. Studies at various pH levels indicate that the capacity of the adsorbents for adsorption of the ionic forms of adsorbate is less than that for the corresponding neutral species. At pH 3.78, the adsorption capacities of the three adsorbents are the highest. Whereas the adsorption property of multi-functional polymeric adsorbent NJ-99 is the largest, which may be attributed to the strong hydrogen-bonding interaction between the amino groups on the resin and the carboxyl group of p-aminobenzoic acid. The trend of the adsorption capacities of the three adsorbents towards p-aminobenzoic acid with the solution pH is in accord with the dissociation curve of the neutral molecular p-aminobenzoic acid. The adsorption forces include π-π interaction, hydrogen-bonding interaction and electrostatic attraction or repulsion when there exist the molecular and ionic adsorbing species at different pHs in aqueous solution.展开更多
In this paper, the membrane capacitance (Cm), which was obtained from the electro- chemical impedance spectroscopy (EIS) method, was used to characterize the effect of pH value on the self-assembled monolayers (SAMs) ...In this paper, the membrane capacitance (Cm), which was obtained from the electro- chemical impedance spectroscopy (EIS) method, was used to characterize the effect of pH value on the self-assembled monolayers (SAMs) of octadecanethiol(18SH) for the first time. The results not only strongly proved that inorganic ions could penetrate the SAMs of 18SH, but also ascertained that SAMs of 18SH were not an absolute of free of ion-penetration. Verifying the existence of pin-holes in the octadecanethiol SAMs was the main contribution of this paper, which coincided with the former conjecture very well.展开更多
This work investigates the relative aggressiveness of nitrate solutions at different pH values on mild steel towards stress corrosion cracking (SCC) and general corrosion. Electrochemical behavior and stress corrosion...This work investigates the relative aggressiveness of nitrate solutions at different pH values on mild steel towards stress corrosion cracking (SCC) and general corrosion. Electrochemical behavior and stress corrosion cracking sus-ceptibility measurements were carried out in 52 Wt% ammonium nitrate solutions at 368° K and various pH values ranging from 0.77 to 9.64. Constant load stress corrosion test at 90% yield stress was conducted. Tested specimens were prepared and examined using the scanning electron microscope (SEM). The potentiodynamic polarization curves for different pH values again emphasized the validity of the gravimetric measurements and hence the mechanism of cracking was attributed to the stress that assisted the dissolution process.展开更多
基金supported by the National Natural Science Foundation of China(Nos.22102073,22075147).
文摘As a versatile and environmentally benign oxidant,hydrogen peroxide(H_(2)O_(2))is highly desired in sanitation,disinfection,environmental remediation,and the chemical industry.Compared with the conventional anthraquinone process,the electrosynthesis of H_(2)O_(2)through the two-electron oxygen reduction reaction(2e^(−)ORR)is an efficient,competitive,and promising avenue.Electrocatalysts and devices are two core factors in 2e^(−)ORR,but the design principles of catalysts for different pH conditions and the development trends of relevant synthesis devices remain unclear.To this end,this review adopts a multiscale perspective to summarize recent advancements in the design principles,catalytic mechanisms,and application prospects of 2e^(−)ORR catalysts,with a particular focus on the influence of pH conditions,aiming at providing guidance for the selective design of advanced 2e^(−)ORR catalysts for highly-efficient H_(2)O_(2)production.Moreover,in response to diverse on-site application demands,we elaborate on the evolution of H_(2)O_(2)electrosynthesis devices,from rotating ring-disk electrodes and H-type cells to diverse flow-type cells.We elaborate on their characteristics and shortcomings,which can be beneficial for their further upgrades and customized applications.These insights may inspire the rational design of innovative catalysts and devices with high performance and wide serviceability for large-scale implementations.
基金supported by the National Natural Science Foundation of China(No.21473175 and No.21273215)the National Key Basic Research Program of China from the Ministry of Science andTechnology of China(No.2015CB932301)
文摘The hydrogen peroxide oxidation reaction (HPOOR) on Au(111) electrode in alkaline solutions with pH values ranging from 10 to 13 was examined systematically. HPOOR activity increased and the slope of the i-E curve decreased with increasing pH. HO2- is suggested to be the main reactive intermediate for HPOOR in alkaline media. The fast kinetics for HPOOR in alkaline solution is facilitated by the electrostatic interaction between the positively charged electrode and the reactive anions (i.e., HO2- and HO-), which increases the concentration of these reactants and the thermodynamic driving force for HO2- oxidation at the reaction plane.
基金support from the National Natural Science Foundation of China(Nos.22272193,22225302,21991151,and 21991150)the Ningbo Natural Science Foundation(No.2022J294)+1 种基金the Yongjiang Talent Introduction Program(No.2021A-115-G)Key Laboratory of Advanced Marine Materials,Ningbo Institute of Materials Technology and Engineering,Chinese Academy of Sciences,Ningbo.(No.2021A-115-G).
文摘The adsorption/desorption of OH*on electrode surfaces is pivotal in numerous electrocatalytic reactions.To understand the effect of electrolyte pH on that process,in this work,an advanced approach combining ab initio molecular dynamics(AIMD)with free energy perturbation is employed to calculate the dehydrogenation free energy of water chemisorbed at differently electrified Pt(111)/electrolyte interfaces.Our findings reveal that the onset potential for OH*formation shifts negatively as the pH increases at low pH condition(pH<4.3),aligning with the cyclic voltammetry curves observed in experimental studies.It indicates the dissociation of chemisorbed water is the primary route for OH*adsorption at low pH condition.Furthermore,it is also found that the variation in dehydrogenation energy across different pH is primarily due to the local hydrogen bonding network surrounding the chemisorbed water.In addition,it is proposed that at high pH conditions OH-oxidation emerges as the primary route for OH*adsorption on Pt(111)constrained by the water chemisorption process.This work provides crucial insights into the pH-dependent adsorption behavior of OH*on the Pt(111)surface and aims to guide the optimization of electrolytes to boost the efficiency of related reactions.
基金supported by the National Natural Science Foundation of China(No.22172151)。
文摘Phosphoric acid/phosphate solu-tions are commonly used as buffer solutions in the fundamental stud-ies in electrochemistry.Informa-tion on the nature of adsorbed(bi)phosphate as well as the do-main structures is of great impor-tance in unveiling the impact on electrochemical processes occur-ring at electrode electrolyte interface.In this work,the pH effect on the adsorption of phosphate related species on Pd(111)electrode has been investigated by cyclic voltammetry over a broad pH range from 1 to 14.Af-ter carefully analyzing the related onset desorption potential of(bi)phosphate adsorbate to the thermodynamic equilibrium potential of the corresponding electrode reactions,three dif-ferent phosphate related adsorbates have been identified,which are highly pH-dependent.Our analysis reveals that the dominant phosphate anions in bulk solution undergo deprotona-tion upon adsorption.At pH<1.5,the main adsorbate on Pd(111)is;H_(2)PO_(4)^(λ_(1)^(-))in solutions with 1.5<pH<7,the main adsorbate changes into.HPO_(4)^(λ_2^(-))At higher pHs,PO_(4)^(λ_(3)^(-))on electrode surface dominates.The exact charging value ofλ_(i),which represents the true va-lence of the(bi)phosphate adsorbate,could be determined using theoretical calculations.In addition,our results can not rule out the possibility of co-adsorbed H_(3)PO_(4)molecules on Pd(111)at pH<1.5,which needs to be proved by infrared spectroscopy in the future.
基金the National Center of Excellence for Environmental and Hazardous Waste Management(NCE-EHWM)the Geology Department of Chulalongkorn University
文摘This study investigated the effects of pH on the transport of Pb 2＋ , Mn 2＋ , Zn 2＋ and Ni 2＋ through lateritic soil columns. Model results by fitting the symmetric breakthrough curves （BTCs） of bromide （Br ） with CXTFIT model suggested that physical non-equilibrium processes were absent in the columns. The heavy metal BTCs were, however, asymmetrical and exhibited a tailing phenomenon, indicating the presence of chemical non-equilibrium processes in the columns. The retardation factors of Pb 2＋ were the largest of the four metal ions at both pH 4.0 （33.3） and pH 5.0 （35.4）. The use of Langmuir isotherm parameters from batch studies with HYDRUS-1D did not predict the BTCs well. Rather the two-site model （TSM） described the heavy metal BTCs better than the equilibrium linear/nonlinear Langmuir model. The fraction of instantaneous sorption sites （ f ） of all four metal ions on the lateritic soil was consistently about 30%–44% of the total sorption sites.
基金financial support from the National Natural Science Foundation of China(21528302)Zhejiang Province Natural Science Foundation(LQ15B060004)
文摘The Co-based catalysts were prepared with different cobalt acetate solutions.Effects of pH value were studied deeply on Fischer–Tropsch synthesis(FTS)through a semi-batch reactor.Among all impregnation solutions(water,butanol,amyl alcohol,acetic acid,nitric acid and ammonium nitrate),the catalyst prepared by NH4NO3solution showed the highest catalytic activity due to its small particle size and high reduction degree.However,the catalyst with the smallest particle size derived from water as impregnation solution exhibited low activity as well as high methane selectivity since it was difficult to be reduced and inactive in FTS.According to FT-IR spectra results,the low intensity of absorbed CO on the catalyst prepared from water solution resulted in low FTS activity.Whereas,the high activity of catalysts prepared from NH4NO3solution could be explained by the high intensity of absorbed CO on the catalysts.The cobalt species on the catalysts prepared under lower pH conditions exhibited smaller particle size distribution as well as lower CO conversion than those prepared at higher pH value.
基金supported by the National Natural Science Foundation of China(21972131)。
文摘In this study,we systematically investigated the effect of proton concentration on the kinetics of the oxygen reduction reaction(ORR)on Pt(111)in acidic solutions.Experimental results demonstrate a rectangular hyperbolic relationship,i.e.,the ORR current excluding the effect of other variables increases with proton concentration and then tends to a constant value.We consider that this is caused by the limitation of ORR kinetics by the trace oxygen concentration in the solution,which determines the upper limit of ORR kinetics.A model of effective concentration is further proposed for rectangular hyperbolic relationships:when the reactant concentration is high enough to reach a critical saturation concentration,the effective reactant concentration will become a constant value.This could be due to the limited concentration of a certain reactant for reactions involving more than one reactant or the limited number of active sites available on the catalyst.Our study provides new insights into the kinetics of electrocatalytic reactions,and it is important for the proper evaluation of catalyst activity and the study of structureperformance relationships.
文摘The oxygen reduction kinetics on polycobaltprotoporphyrin(PCoPP)film has been examined with the rotating disc electrode technique in O_2-saturated solution of various pH.PCoPP film promotes the oxygen reduction process via two electrons to produce peroxide over wide pH range. When pH value of solution decreases,catalytic activity of PCoPP film increases.Possible catalytic mechanisms have been proposed for oxygen reduction.
文摘STUDIES of radiation chemistry on methionine (Met) were very active in previous years because of its actions of radioprotection to biological systems by quenching·OH radicals. On the other hand, people have paid more and more attention to the researches on the phosphorylation of the biological polymolecules. It is wall known that phosphate ester is regarded as the deposi-
基金This work was supported by the Opening Foundation of Jiangsu Provincial Key Laboratory of Coastal Wetland Bioresources and Environmental Protection of China (No. JLCBE05006).
文摘In the present study the adsorptive properties of p-aminobenzoic acid with hypercrosslinked and multi-functional polymeric adsorbents at different solution pHs were systematically investigated in accordance with the particular physicochemical characteristics of the aromatic amphoteric compound involving both Lewis acid and Lewis base functional groups. It was found that the equilibrium adsorption data of the three polymeric adsorbents fitted well in the Langmuir and Freundlich isotherm equations. Studies at various pH levels indicate that the capacity of the adsorbents for adsorption of the ionic forms of adsorbate is less than that for the corresponding neutral species. At pH 3.78, the adsorption capacities of the three adsorbents are the highest. Whereas the adsorption property of multi-functional polymeric adsorbent NJ-99 is the largest, which may be attributed to the strong hydrogen-bonding interaction between the amino groups on the resin and the carboxyl group of p-aminobenzoic acid. The trend of the adsorption capacities of the three adsorbents towards p-aminobenzoic acid with the solution pH is in accord with the dissociation curve of the neutral molecular p-aminobenzoic acid. The adsorption forces include π-π interaction, hydrogen-bonding interaction and electrostatic attraction or repulsion when there exist the molecular and ionic adsorbing species at different pHs in aqueous solution.
基金This work was supported by the NNSFC (29973026).
文摘In this paper, the membrane capacitance (Cm), which was obtained from the electro- chemical impedance spectroscopy (EIS) method, was used to characterize the effect of pH value on the self-assembled monolayers (SAMs) of octadecanethiol(18SH) for the first time. The results not only strongly proved that inorganic ions could penetrate the SAMs of 18SH, but also ascertained that SAMs of 18SH were not an absolute of free of ion-penetration. Verifying the existence of pin-holes in the octadecanethiol SAMs was the main contribution of this paper, which coincided with the former conjecture very well.
文摘This work investigates the relative aggressiveness of nitrate solutions at different pH values on mild steel towards stress corrosion cracking (SCC) and general corrosion. Electrochemical behavior and stress corrosion cracking sus-ceptibility measurements were carried out in 52 Wt% ammonium nitrate solutions at 368° K and various pH values ranging from 0.77 to 9.64. Constant load stress corrosion test at 90% yield stress was conducted. Tested specimens were prepared and examined using the scanning electron microscope (SEM). The potentiodynamic polarization curves for different pH values again emphasized the validity of the gravimetric measurements and hence the mechanism of cracking was attributed to the stress that assisted the dissolution process.
