The electrochemical performance of CoO-filled multi-walled carbon nanotubes(MWCNTs) is described. MWCNTs were purified, opened and filled with cobalt salt in one-step by wet-chemistry route. Followed by calcinations i...The electrochemical performance of CoO-filled multi-walled carbon nanotubes(MWCNTs) is described. MWCNTs were purified, opened and filled with cobalt salt in one-step by wet-chemistry route. Followed by calcinations in Ar atmosphere, the salt filled in the MWCNTs decomposed to CoO subsequently. Structural characterization of the composite material by X-ray diffraction and transmission electron microscopy showed that MWCNTs were filled by discrete nano-size CoO. Compared to the MWCNTs purified by HNO3, the CoO-filled MWCNTs exhibited higher capacity and better cyclability during galvanastatic charge-discharge cycling and cyclic voltammetry (CV) tests.展开更多
Over the past few years, electrocatalysis for the oxygen reduction reaction in alkaline solutions has undergone tremendous advances, and non-precious metal catalysts are of prime interest. In this study, we present a ...Over the past few years, electrocatalysis for the oxygen reduction reaction in alkaline solutions has undergone tremendous advances, and non-precious metal catalysts are of prime interest. In this study, we present a highly promising CoO@Co/N-C (where N-C represents a N-doped carbon material) catalyst, achieving an onset potential of 0.99 V (versus the reversible hydrogen electrode (RHE)) and a limiting current density of 7.07 mA-cm-2 (at 0.3 V versus RHE) at a rotation rate of 2,500 rpm in an O2-saturated 0.1 M KOH solution, comparable to a commercial Pt/C catalyst. The H2--O2 alkaline fuel cell test of CoO@Co/N-C as the cathode reveals a maximum power density of 237 mW.cm 2. Detailed investigation clarifies that a synergistic effect, induced by C-N, Co-N-C, and CoO/Co moieties, is responsible for the bulk of the gain in catalytic activity.展开更多
Higher alcohol synthesis directly from syngas is highly desirable as one of the efficient non-petroleum energy conversion routes.Co^(0)–CoO catalysts showed great potential for this reaction,but the alcohol selectivi...Higher alcohol synthesis directly from syngas is highly desirable as one of the efficient non-petroleum energy conversion routes.Co^(0)–CoO catalysts showed great potential for this reaction,but the alcohol selectivity still needs to be improved and the crystal structure effect of Co^(0)on catalytic behaviors lacks investigation.Here,a series of tetrahedrally coordinated Co^(0)polymorphs were prepared by a thermal decomposition method,which consisted of wurtzite CoO and zinc blende CoO with varied contents.After diluting with SiO_(2),the catalyst showed excellent performance for higher alcohol synthesis with ROH selectivity of 45.8%and higher alcohol distribution of 84.1 wt%under the CO conversion of 38.0%.With increasing the content of wurtzite CoO,the Co^(0)/Co^(2+)ratio gradually increased in the spent catalysts,while the proportion of highly active hexagonal close packed cobalt in Co^(0)decreased,leading to first decreased then increased CO conversion.Moreover,the higher content of zinc blende CoO in fresh catalyst facilitated the retention of more Co^(2+)sites in spent catalysts,promoting the ROH selectivity but slightly decreasing the distribution of higher alcohols.The catalyst with 40%wurtzite CoO obtained the optimal performance with a space time yield toward higher alcohols of 7.9 mmol·gcat^(-1)·h^(-1).展开更多
Shape control of nanocrystals has become a significant subject in materials science.In this work,we describe a convenient way to achieve morphology-controllable synthesis of CoO nanocrystals including octahedrons and ...Shape control of nanocrystals has become a significant subject in materials science.In this work,we describe a convenient way to achieve morphology-controllable synthesis of CoO nanocrystals including octahedrons and spheres as well as LiCoO_(2) polyhedrons and spheres.In particular,we explain the formation of CoO octahedrons exposing only high-energy(111)facets using theoretical calculations;these should also be a useful tool for directing future face-controlled preparation of other nanocrystals.More importantly,the as-obtained LiCoO_(2) nanocrystals showed different electrochemical performance depending on their morphology,indicating that Li-insertion/deintercalation dynamics might be crystal face-sensitive.展开更多
Combining nanomaterials with complementary properties in a well-designed structure is an effective tactic to exploit multifunctional, high-performance materials for the energy conversion and storage. Nonprecious metal...Combining nanomaterials with complementary properties in a well-designed structure is an effective tactic to exploit multifunctional, high-performance materials for the energy conversion and storage. Nonprecious metal catalysts, such as cobalt oxide, with superior activity and excellent stability to other catalysts are widely desired. Nevertheless, the performance of CoO nanoparticles as an electrode material were significantly limit for its inferior conductivity, dissolution, and high cohesion. Herein, we grow ultrafine cobalt monoxide to decorate the interlayer and surface of the Ti3C2 Txnanosheets via a hydrothermal method companied by calcination. The layered MXenes act as the underlying conductive substrate,which not only increase the electron transfer rate at the interface but also greatly improve the electrochemical properties of the nanosized Co O particles by restricting the aggregation of CoO. The resulting CoO/Ti3C2 Txnanomaterial is applied as oxygen electrode for lithium-oxygen battery and achieves more than 160 cycles and first cycle capacity of 16,220 mAh g-1 at 100 mA g-1. This work paves a promising avenue for constructing a bi-functional catalyst by coupling the active component of a transition metal oxide(TMO) with the MXene materials in lithium-oxygen battery.展开更多
文摘The electrochemical performance of CoO-filled multi-walled carbon nanotubes(MWCNTs) is described. MWCNTs were purified, opened and filled with cobalt salt in one-step by wet-chemistry route. Followed by calcinations in Ar atmosphere, the salt filled in the MWCNTs decomposed to CoO subsequently. Structural characterization of the composite material by X-ray diffraction and transmission electron microscopy showed that MWCNTs were filled by discrete nano-size CoO. Compared to the MWCNTs purified by HNO3, the CoO-filled MWCNTs exhibited higher capacity and better cyclability during galvanastatic charge-discharge cycling and cyclic voltammetry (CV) tests.
文摘Over the past few years, electrocatalysis for the oxygen reduction reaction in alkaline solutions has undergone tremendous advances, and non-precious metal catalysts are of prime interest. In this study, we present a highly promising CoO@Co/N-C (where N-C represents a N-doped carbon material) catalyst, achieving an onset potential of 0.99 V (versus the reversible hydrogen electrode (RHE)) and a limiting current density of 7.07 mA-cm-2 (at 0.3 V versus RHE) at a rotation rate of 2,500 rpm in an O2-saturated 0.1 M KOH solution, comparable to a commercial Pt/C catalyst. The H2--O2 alkaline fuel cell test of CoO@Co/N-C as the cathode reveals a maximum power density of 237 mW.cm 2. Detailed investigation clarifies that a synergistic effect, induced by C-N, Co-N-C, and CoO/Co moieties, is responsible for the bulk of the gain in catalytic activity.
基金support from the National Natural Science Foundation of China(Grant Nos.22108199,22278317,and 22022811)the China Postdoctoral Science Foundation(Grant No.2021TQ0239)。
文摘Higher alcohol synthesis directly from syngas is highly desirable as one of the efficient non-petroleum energy conversion routes.Co^(0)–CoO catalysts showed great potential for this reaction,but the alcohol selectivity still needs to be improved and the crystal structure effect of Co^(0)on catalytic behaviors lacks investigation.Here,a series of tetrahedrally coordinated Co^(0)polymorphs were prepared by a thermal decomposition method,which consisted of wurtzite CoO and zinc blende CoO with varied contents.After diluting with SiO_(2),the catalyst showed excellent performance for higher alcohol synthesis with ROH selectivity of 45.8%and higher alcohol distribution of 84.1 wt%under the CO conversion of 38.0%.With increasing the content of wurtzite CoO,the Co^(0)/Co^(2+)ratio gradually increased in the spent catalysts,while the proportion of highly active hexagonal close packed cobalt in Co^(0)decreased,leading to first decreased then increased CO conversion.Moreover,the higher content of zinc blende CoO in fresh catalyst facilitated the retention of more Co^(2+)sites in spent catalysts,promoting the ROH selectivity but slightly decreasing the distribution of higher alcohols.The catalyst with 40%wurtzite CoO obtained the optimal performance with a space time yield toward higher alcohols of 7.9 mmol·gcat^(-1)·h^(-1).
基金This work was supported by the National Natural Science Foundation of China(NSFC)(No.90606006)and the State Key Project of Fundamental Research for Nanoscience and Nanotechnology(No.2006CB932300).
文摘Shape control of nanocrystals has become a significant subject in materials science.In this work,we describe a convenient way to achieve morphology-controllable synthesis of CoO nanocrystals including octahedrons and spheres as well as LiCoO_(2) polyhedrons and spheres.In particular,we explain the formation of CoO octahedrons exposing only high-energy(111)facets using theoretical calculations;these should also be a useful tool for directing future face-controlled preparation of other nanocrystals.More importantly,the as-obtained LiCoO_(2) nanocrystals showed different electrochemical performance depending on their morphology,indicating that Li-insertion/deintercalation dynamics might be crystal face-sensitive.
基金supported by the National Natural Science Foundations of China (Grants:21871028,21771024)。
文摘Combining nanomaterials with complementary properties in a well-designed structure is an effective tactic to exploit multifunctional, high-performance materials for the energy conversion and storage. Nonprecious metal catalysts, such as cobalt oxide, with superior activity and excellent stability to other catalysts are widely desired. Nevertheless, the performance of CoO nanoparticles as an electrode material were significantly limit for its inferior conductivity, dissolution, and high cohesion. Herein, we grow ultrafine cobalt monoxide to decorate the interlayer and surface of the Ti3C2 Txnanosheets via a hydrothermal method companied by calcination. The layered MXenes act as the underlying conductive substrate,which not only increase the electron transfer rate at the interface but also greatly improve the electrochemical properties of the nanosized Co O particles by restricting the aggregation of CoO. The resulting CoO/Ti3C2 Txnanomaterial is applied as oxygen electrode for lithium-oxygen battery and achieves more than 160 cycles and first cycle capacity of 16,220 mAh g-1 at 100 mA g-1. This work paves a promising avenue for constructing a bi-functional catalyst by coupling the active component of a transition metal oxide(TMO) with the MXene materials in lithium-oxygen battery.