Login In
2023 Volume 42 Issue 11
2023, 42(11): 100021
doi: 10.1016/j.cjsc.2023.100021
Abstract:
Electrochemical energy devices such as fuel cells have received extensive concern in recent decades. However, the commercial applications of fuel cells have been restricted by the slow kinetics of oxygen reduction reaction (ORR). Pd-based fuel cell catalysts are strong candidates for enhanced ORR activities, especially under alkaline conditions. Therefore, extensive exploration has been made to improve the performance of Pd-based nanocatalysts for oxygen reduction reaction. This paper reviews the research progress of preparation, electrocatalytic performance, and in-situ characterization of various Pd-based oxygen reduction catalysts, from zero-dimensional nanoparticles, to one-dimensional nanowires, to two-dimensional nanosheets, and to Pd single-atom catalysts. It may provide some help for improving the activity of Pd-based catalysts and understanding the reaction mechanisms and structure-activity relationships.
Electrochemical energy devices such as fuel cells have received extensive concern in recent decades. However, the commercial applications of fuel cells have been restricted by the slow kinetics of oxygen reduction reaction (ORR). Pd-based fuel cell catalysts are strong candidates for enhanced ORR activities, especially under alkaline conditions. Therefore, extensive exploration has been made to improve the performance of Pd-based nanocatalysts for oxygen reduction reaction. This paper reviews the research progress of preparation, electrocatalytic performance, and in-situ characterization of various Pd-based oxygen reduction catalysts, from zero-dimensional nanoparticles, to one-dimensional nanowires, to two-dimensional nanosheets, and to Pd single-atom catalysts. It may provide some help for improving the activity of Pd-based catalysts and understanding the reaction mechanisms and structure-activity relationships.
2023, 42(11): 100031
doi: 10.1016/j.cjsc.2023.100031
Abstract:
Green hydrogen energy developed through electrochemistry is one of the solutions to current energy problems. The less noble metal ruthenium (Ru) plays an important role in alkaline electrocatalytic hydrogen evolution reaction (HER) as an effective electrocatalyst. Nevertheless, the high cost (> 110 RMB per gram) hinders the large-scale application of Ru in industrial hydrogen production. Moreover, the strong adsorption of OH* intermediates over Ru limits the electrocatalytic performance in alkaline HER. Here, we report the Mo-doped Ru nanocluster embedded on N-doped carbon framework (RuMo/NC) as alkaline HER catalyst, which shows excellent catalytic performance with an overpotential of 24.2 mV to reach 10 mA cm-2 with only 0.4 wt% of Ru, much lower than that of most reported Ru-based catalysts. DFT calculations reveal the introduction of Mo has improved the activity by alleviating the poisoning effect of OH* over Ru in HER. Through fully utilizing Ru in the catalyst, this work marks a step forward in the development of Ru-based catalysts in alkaline HER.
Green hydrogen energy developed through electrochemistry is one of the solutions to current energy problems. The less noble metal ruthenium (Ru) plays an important role in alkaline electrocatalytic hydrogen evolution reaction (HER) as an effective electrocatalyst. Nevertheless, the high cost (> 110 RMB per gram) hinders the large-scale application of Ru in industrial hydrogen production. Moreover, the strong adsorption of OH* intermediates over Ru limits the electrocatalytic performance in alkaline HER. Here, we report the Mo-doped Ru nanocluster embedded on N-doped carbon framework (RuMo/NC) as alkaline HER catalyst, which shows excellent catalytic performance with an overpotential of 24.2 mV to reach 10 mA cm-2 with only 0.4 wt% of Ru, much lower than that of most reported Ru-based catalysts. DFT calculations reveal the introduction of Mo has improved the activity by alleviating the poisoning effect of OH* over Ru in HER. Through fully utilizing Ru in the catalyst, this work marks a step forward in the development of Ru-based catalysts in alkaline HER.
2023, 42(11): 100108
doi: 10.1016/j.cjsc.2023.100108
Abstract:
NASICON type Li3Zr2Si2PO12 can be synthesized via cation exchange method with Na3Zr2Si2PO12 as precursor, which retains the skeleton structure and achieves an ionic conductivity higher than 3 mS cm-1 at room temperature. However, large-scale fabrication via cation exchange reaction seems unlikely considering the expensive precursors and complicated preparation process. Herein, the viability of solid-state reaction to prepare Li3Zr2Si2PO12 is explored, which has important implication for its industrialization. The sintering was conducted using the raw materials of LiOH, SiO2, ZrO2 and NH4H2PO4 with the nominal stoichiometric ratio of Li3Zr2Si2PO12. The results show that the final product is a Li3PO4·2ZrSiO4 composite with negligible Li+ conductivity, other than the expected Li3Zr2Si2PO12 with high Li+ conductivity. Combined with thermodynamic calculations based on density functional theory (DFT), the competition between Li3PO4·2ZrSiO4 and Li3Zr2Si2PO12 with NASICON phase is analyzed. It was found that the formation energy (ΔG) of Li3PO4·2ZrSiO4 is lower than that of Li3Zr2Si2PO12. In addition, the decomposition of Li3Zr2Si2PO12 with Li3PO4·2ZrSiO4 as products is a thermodynamically spontaneous reaction. The influences related to the coordination structures on the structural stability of NZSP are discussed as well. These results demonstrate that the fabrication of Li3Zr2Si2PO12 through high-temperature sintering is difficult, and the development of a synthetic method with mild conditions is essential for the Li3Zr2Si2PO12 preparation.
NASICON type Li3Zr2Si2PO12 can be synthesized via cation exchange method with Na3Zr2Si2PO12 as precursor, which retains the skeleton structure and achieves an ionic conductivity higher than 3 mS cm-1 at room temperature. However, large-scale fabrication via cation exchange reaction seems unlikely considering the expensive precursors and complicated preparation process. Herein, the viability of solid-state reaction to prepare Li3Zr2Si2PO12 is explored, which has important implication for its industrialization. The sintering was conducted using the raw materials of LiOH, SiO2, ZrO2 and NH4H2PO4 with the nominal stoichiometric ratio of Li3Zr2Si2PO12. The results show that the final product is a Li3PO4·2ZrSiO4 composite with negligible Li+ conductivity, other than the expected Li3Zr2Si2PO12 with high Li+ conductivity. Combined with thermodynamic calculations based on density functional theory (DFT), the competition between Li3PO4·2ZrSiO4 and Li3Zr2Si2PO12 with NASICON phase is analyzed. It was found that the formation energy (ΔG) of Li3PO4·2ZrSiO4 is lower than that of Li3Zr2Si2PO12. In addition, the decomposition of Li3Zr2Si2PO12 with Li3PO4·2ZrSiO4 as products is a thermodynamically spontaneous reaction. The influences related to the coordination structures on the structural stability of NZSP are discussed as well. These results demonstrate that the fabrication of Li3Zr2Si2PO12 through high-temperature sintering is difficult, and the development of a synthetic method with mild conditions is essential for the Li3Zr2Si2PO12 preparation.
2023, 42(11): 100116
doi: 10.1016/j.cjsc.2023.100116
Abstract:
Lithium-based semi-solid flow battery (LSSFB) is expected to be applied in the field of large-scale energy storage. However, the rate performance of LSSFBs is unsatisfied due to the poor conductivity of active materials and the unstable contact with conductive additives. Herein, carbon coated MnO quantum dots derived from MIL-100(Mn) were prepared. Such MnO quantum dots and carbon framework composite can not only increase the reactive active sites of MnO, but also avoid their agglomeration in the lithiation/delithiation process. Furthermore, the carbon framework and multi-walled carbon nanotubes (MWCNTs) are conducive to the rapid transport of electrons and can inhibit the volume expansion of MnO, achieving the high-rate performance and long cycling life. Moreover, MWCNTs can increase the suspension of the material and ensure the long-term stability of the slurry. These advantages endow the LSSFBs with high rate and long cycling performance. This work provides a promising strategy for the preparation of high-rate slurry electrode materials.
Lithium-based semi-solid flow battery (LSSFB) is expected to be applied in the field of large-scale energy storage. However, the rate performance of LSSFBs is unsatisfied due to the poor conductivity of active materials and the unstable contact with conductive additives. Herein, carbon coated MnO quantum dots derived from MIL-100(Mn) were prepared. Such MnO quantum dots and carbon framework composite can not only increase the reactive active sites of MnO, but also avoid their agglomeration in the lithiation/delithiation process. Furthermore, the carbon framework and multi-walled carbon nanotubes (MWCNTs) are conducive to the rapid transport of electrons and can inhibit the volume expansion of MnO, achieving the high-rate performance and long cycling life. Moreover, MWCNTs can increase the suspension of the material and ensure the long-term stability of the slurry. These advantages endow the LSSFBs with high rate and long cycling performance. This work provides a promising strategy for the preparation of high-rate slurry electrode materials.
2023, 42(11): 100156
doi: 10.1016/j.cjsc.2023.100156
Abstract:
In this perspective, we embark on a brief exploration of recent advancements in the synthesis of alloy nanocrystals, with a particular focus on enhancing compositional homogeneity and tunability. We discuss the progress made in typical synthesis paradigms, encompassing conventional impregnation, wet-chemical reduction/pyrolysis, and the newly developed active-hydrogen-involved interfacial reduction strategy. Furthermore, we offer personal insights into the significance of these synthesis paradigms and their potential implications for future research and applications.
In this perspective, we embark on a brief exploration of recent advancements in the synthesis of alloy nanocrystals, with a particular focus on enhancing compositional homogeneity and tunability. We discuss the progress made in typical synthesis paradigms, encompassing conventional impregnation, wet-chemical reduction/pyrolysis, and the newly developed active-hydrogen-involved interfacial reduction strategy. Furthermore, we offer personal insights into the significance of these synthesis paradigms and their potential implications for future research and applications.
2023, 42(11): 100157
doi: 10.1016/j.cjsc.2023.100157
Abstract:
Direct methanol fuel cells have the advantages of simple system, convenient operation, high conversion rate and low carbon emission, which are considered as the environmental and friendly energy conversion devices. However, the low activity, CO-tolerance and high cost of anode catalysts restrict the large-scale commercial applications. Therefore, it is of great practical significance to design and construct the anodic catalysts with high activity, stability and low cost for methanol oxidation reaction. In this work, the PtM/Nb2O5–C (M = Co, Sn, Ni) catalysts are synthesized by the ethylene glycol solvothermal method using transition metal oxide Nb2O5 as the support. The catalytic performance of different catalysts is further evaluated for alkaline MOR. The results show that the introduction of Ni (existing in Ni2+ and Ni3+) has the most obvious improvement for alkaline MOR performance. By adjusting the doped ratio of Pt:Ni, it is shown that PtNi/Nb2O5–C has the highest mass activity (3877.9 mA·mgPt-1), 12 times that of the commercial Pt/C catalyst. CV, LSV, Tafel and EIS analyses show that PtNi/Nb2O5–C has the lowest onset potential and charge transfer resistance, and the fastest electrocatalytic oxidation rate of methanol. CA tests show that the electrochemical stability is also significantly improved with the introduction of Nb2O5 and Ni. Combined with the structural characterization and electrochemical tests, it is found that the evident electronic effect among Pt and Ni, Nb2O5 and the hydroxyl brought from Ni species are mainly ascribed for enhancing the activity, CO resistance and stability of PtNi/Nb2O5–C.
Direct methanol fuel cells have the advantages of simple system, convenient operation, high conversion rate and low carbon emission, which are considered as the environmental and friendly energy conversion devices. However, the low activity, CO-tolerance and high cost of anode catalysts restrict the large-scale commercial applications. Therefore, it is of great practical significance to design and construct the anodic catalysts with high activity, stability and low cost for methanol oxidation reaction. In this work, the PtM/Nb2O5–C (M = Co, Sn, Ni) catalysts are synthesized by the ethylene glycol solvothermal method using transition metal oxide Nb2O5 as the support. The catalytic performance of different catalysts is further evaluated for alkaline MOR. The results show that the introduction of Ni (existing in Ni2+ and Ni3+) has the most obvious improvement for alkaline MOR performance. By adjusting the doped ratio of Pt:Ni, it is shown that PtNi/Nb2O5–C has the highest mass activity (3877.9 mA·mgPt-1), 12 times that of the commercial Pt/C catalyst. CV, LSV, Tafel and EIS analyses show that PtNi/Nb2O5–C has the lowest onset potential and charge transfer resistance, and the fastest electrocatalytic oxidation rate of methanol. CA tests show that the electrochemical stability is also significantly improved with the introduction of Nb2O5 and Ni. Combined with the structural characterization and electrochemical tests, it is found that the evident electronic effect among Pt and Ni, Nb2O5 and the hydroxyl brought from Ni species are mainly ascribed for enhancing the activity, CO resistance and stability of PtNi/Nb2O5–C.
2023, 42(11): 100160
doi: 10.1016/j.cjsc.2023.100160
Abstract:
Core-shell nanostructures usually exhibit tunable catalytic properties in comparison with their single core or shell counterpart due to electronic interaction and lattice strain between the core and shell regions. Herein, we report the intriguing evolution of copper (Cu) shells on the gold (Au) cores at different Au/Cu precursor ratios during the synthesis of core-shell Au–Cu nanoparticles at an organic medium via seed-mediated growth method. In brief, at relatively low Cu ratios, quasi-spherical Au–Cu nanoparticles with conventional core-shell structures are the majority products, in which the Cu shell thickness increases with the increase of Cu precursor ratios. The difference is that at high Cu ratios, the Cu shells no longer increase their thickness, but evolve into a dendritic structure. Interestingly, the core-shell Au–Cu nanoparticles with dendritic Cu shells could be transformed into interesting Au–Cu cage-bell structures after a ripening process at elevated temperature. Further, through galvanic replacement reaction with Pt precursors, the thin Cu shells could be converted into CuPt alloy shells on the Au cores, which exhibit enhanced activity towards methanol oxidation reaction with satisfactory durability, in comparison with that of commercial Pt/C catalysts.
Core-shell nanostructures usually exhibit tunable catalytic properties in comparison with their single core or shell counterpart due to electronic interaction and lattice strain between the core and shell regions. Herein, we report the intriguing evolution of copper (Cu) shells on the gold (Au) cores at different Au/Cu precursor ratios during the synthesis of core-shell Au–Cu nanoparticles at an organic medium via seed-mediated growth method. In brief, at relatively low Cu ratios, quasi-spherical Au–Cu nanoparticles with conventional core-shell structures are the majority products, in which the Cu shell thickness increases with the increase of Cu precursor ratios. The difference is that at high Cu ratios, the Cu shells no longer increase their thickness, but evolve into a dendritic structure. Interestingly, the core-shell Au–Cu nanoparticles with dendritic Cu shells could be transformed into interesting Au–Cu cage-bell structures after a ripening process at elevated temperature. Further, through galvanic replacement reaction with Pt precursors, the thin Cu shells could be converted into CuPt alloy shells on the Au cores, which exhibit enhanced activity towards methanol oxidation reaction with satisfactory durability, in comparison with that of commercial Pt/C catalysts.
2023, 42(11): 100171
doi: 10.1016/j.cjsc.2023.100171
Abstract:
The application of Li–O2 batteries (LOBs) with ultra-high theoretical energy density is limited due to the slow redox kinetics and serious side reactions, especially in high-rate cycles. Herein, CeO2 is constructed on the surface of Mn2O3 through an interface engineering strategy, and Mn2O3@CeO2 heterojunction with good activity and stability at high current density is prepared. The interfacial properties of catalyst and formation mechanism of Li2O2 are deeply studied by density functional theory (DFT) and experiments, revealing the charge-discharge reaction mechanism of LOBs. The results show that the strong electron coupling between Mn2O3 and CeO2 can promote the formation of oxygen vacancies. Heterojunction combined with oxygen vacancy can improve the affinity for O2 and LiO2 reaction intermediates, inducing the formation of thin-film Li2O2 with low potential and easy decomposition, thus improving the cycle stability at high current density. Consequently, it achieved a high specific capacity of 12545 at 1000 mA g-1 and good cyclability of 120 cycles at 4000 mA g-1. This work thus sheds light on designing efficient and stable catalysts for LOBs under high current density.
The application of Li–O2 batteries (LOBs) with ultra-high theoretical energy density is limited due to the slow redox kinetics and serious side reactions, especially in high-rate cycles. Herein, CeO2 is constructed on the surface of Mn2O3 through an interface engineering strategy, and Mn2O3@CeO2 heterojunction with good activity and stability at high current density is prepared. The interfacial properties of catalyst and formation mechanism of Li2O2 are deeply studied by density functional theory (DFT) and experiments, revealing the charge-discharge reaction mechanism of LOBs. The results show that the strong electron coupling between Mn2O3 and CeO2 can promote the formation of oxygen vacancies. Heterojunction combined with oxygen vacancy can improve the affinity for O2 and LiO2 reaction intermediates, inducing the formation of thin-film Li2O2 with low potential and easy decomposition, thus improving the cycle stability at high current density. Consequently, it achieved a high specific capacity of 12545 at 1000 mA g-1 and good cyclability of 120 cycles at 4000 mA g-1. This work thus sheds light on designing efficient and stable catalysts for LOBs under high current density.
2023, 42(11): 100172
doi: 10.1016/j.cjsc.2023.100172
Abstract:
Herein we present a fluorinated metal-organic framework of {(Me2NH2)[Ni3(μ3-OH)(CF3-BPDC-CF3)3(tpt)]}n (1) constructed from 2,2'-bis(trifluoromethyl)biphenyl-4,4'-dicarboxylic (CF3-BPDC-CF32-) and 2,4,6-tri(4-pyridyl)-1,3,5-triazine (tpt) ligands, which is developed for separating propane (C3H8) and ethane (C2H6) from natural gas. Compound 1 preferentially adsorbs C3H8 and C2H6 over CH4 demonstrated by gas adsorption experiments. The presence of trifluoromethyl groups on the biphenyl-4,4'-dicarboxylic ligands facilitates the highly polarized micropore environments for compound 1, thus providing suitable micorpores for capturing the C3H8 and C2H6 molecules with larger polarizabilities and sizes compared to CH4 molecule. The dynamic mixture breakthrough experiments showed that compound 1 can separate C3H8 and C2H6 from the ternary CH4/C2H6/C3H8 mixtures efficiently, endowing compound 1 with excellent methane purification ability.
Herein we present a fluorinated metal-organic framework of {(Me2NH2)[Ni3(μ3-OH)(CF3-BPDC-CF3)3(tpt)]}n (1) constructed from 2,2'-bis(trifluoromethyl)biphenyl-4,4'-dicarboxylic (CF3-BPDC-CF32-) and 2,4,6-tri(4-pyridyl)-1,3,5-triazine (tpt) ligands, which is developed for separating propane (C3H8) and ethane (C2H6) from natural gas. Compound 1 preferentially adsorbs C3H8 and C2H6 over CH4 demonstrated by gas adsorption experiments. The presence of trifluoromethyl groups on the biphenyl-4,4'-dicarboxylic ligands facilitates the highly polarized micropore environments for compound 1, thus providing suitable micorpores for capturing the C3H8 and C2H6 molecules with larger polarizabilities and sizes compared to CH4 molecule. The dynamic mixture breakthrough experiments showed that compound 1 can separate C3H8 and C2H6 from the ternary CH4/C2H6/C3H8 mixtures efficiently, endowing compound 1 with excellent methane purification ability.
