Cobalt spinel oxides are ac lass of promising transition metal (TM) oxides for catalyzing oxygen evolution reaction (OER). Their catalytic activity depends on the electronic structure.I naspinel oxide lattice,e acho xygen anion is shared amongst its four nearest transition metal cations,ofwhich one is located within the tetrahedral interstices and the remaining three cations are in the octahedral interstices. This work uncovered the influence of oxygen anion charge distribution on the electronic structure of the redox-active building blockC o ÀO. The charge of oxygen anion tends to shift toward the octahedral-occupied Co instead of tetrahedraloccupied Co,w hich hence produces strong orbital interaction between octahedral Co and O. Thus,t he OER activity can be promoted by pushing more Co into the octahedral site or shifting the oxygen charge towards the redox-active metal center in CoO 6 octahedra.The clean-burning hydrogen fuel, if produced by electrochemical water splitting, would revolutionize the global energy infrastructure.T he major limitation of water splitting is the sluggish oxygen evolution reaction (OER) at the anode. [1] To date,the most efficient OER electrocatalysts are made from noble metal ruthenium or iridium. In order to meet the broader goal of sustainability,e xploring earthabundant transition metal (TM) oxide catalysts have been prioritized. [1b, 2] Better understanding of the OER reaction on TM oxides is necessary to this end. It has been found that the surface redox-active centers in TM oxides play ak ey role in oxygen electrocatalysis. [3] Thec onventional perception of oxygen evolution regards the redox-active metallic center as the active site and it is the redox ability of TM that mediates the transition of [M n+ ÀOH ad ]/[M n+1 ÀO ad ]d uring OER. [3,4] However,t he redox of late transition metal oxides (e.g., Coand Ni-based) could involve both the transition metal and oxygen ligand due to the increased orbital hybridization between TM 3d and O2 p. [2,5] Earlier reports had demonstrated that the energy in TM 3d orbital cannot be treated in isolation from O2pwhen there is significant overlap between TM 3d and O2 p. Recent studies on oxygen-deficient perovskite oxides reveal that the oxygen anion could also act as the redox partner in OER. [6] Direct evidence for lattice oxygen participated OER using in situ 18 Oi sotope labelling mass spectrometry has been given by Alexis et al. [6b] Thefact that the oxygen anion can also act as the redox-active center emphasizes the importance of considering TM À Obond as the redox-active building block. More recently,t he covalent character (covalency) of TM Bs ite ÀOb ond (TM B the TM in B site) has been proposed to be adominating factor in OER on perovskite oxides. [6b, 7] TheA -site rare-earth metals (low in electronegativity) tend to form an ionic bond with Oa nd weaken the influence of M A -O block on OER. Spinel oxides, ah uge crystal family for oxygen electrocatalysis, [2,4,8] require more complex analysis because the tetrahedral and octahe...

Cobalt spinel oxides are ac lass of promising transition metal (TM) oxides for catalyzing oxygen evolution reaction (OER). Their catalytic activity depends on the electronic structure.I naspinel oxide lattice,e acho xygen anion is shared amongst its four nearest transition metal cations,ofwhich one is located within the tetrahedral interstices and the remaining three cations are in the octahedral interstices. This work uncovered the influence of oxygen anion charge distribution on the electronic structure of the redox-active building blockC o ÀO. The charge of oxygen anion tends to shift toward the octahedral-occupied Co instead of tetrahedraloccupied Co,w hich hence produces strong orbital interaction between octahedral Co and O. Thus,t he OER activity can be promoted by pushing more Co into the octahedral site or shifting the oxygen charge towards the redox-active metal center in CoO 6 octahedra.The clean-burning hydrogen fuel, if produced by electrochemical water splitting, would revolutionize the global energy infrastructure.T he major limitation of water splitting is the sluggish oxygen evolution reaction (OER) at the anode. [1] To date,the most efficient OER electrocatalysts are made from noble metal ruthenium or iridium. In order to meet the broader goal of sustainability,e xploring earthabundant transition metal (TM) oxide catalysts have been prioritized. [1b, 2] Better understanding of the OER reaction on TM oxides is necessary to this end. It has been found that the surface redox-active centers in TM oxides play ak ey role in oxygen electrocatalysis. [3] Thec onventional perception of oxygen evolution regards the redox-active metallic center as the active site and it is the redox ability of TM that mediates the transition of [M n+ ÀOH ad ]/[M n+1 ÀO ad ]d uring OER. [3,4] However,t he redox of late transition metal oxides (e.g., Coand Ni-based) could involve both the transition metal and oxygen ligand due to the increased orbital hybridization between TM 3d and O2 p. [2,5] Earlier reports had demonstrated that the energy in TM 3d orbital cannot be treated in isolation from O2pwhen there is significant overlap between TM 3d and O2 p. Recent studies on oxygen-deficient perovskite oxides reveal that the oxygen anion could also act as the redox partner in OER. [6] Direct evidence for lattice oxygen participated OER using in situ 18 Oi sotope labelling mass spectrometry has been given by Alexis et al. [6b] Thefact that the oxygen anion can also act as the redox-active center emphasizes the importance of considering TM À Obond as the redox-active building block. More recently,t he covalent character (covalency) of TM Bs ite ÀOb ond (TM B the TM in B site) has been proposed to be adominating factor in OER on perovskite oxides. [6b, 7] TheA -site rare-earth metals (low in electronegativity) tend to form an ionic bond with Oa nd weaken the influence of M A -O block on OER. Spinel oxides, ah uge crystal family for oxygen electrocatalysis, [2,4,8] require more complex analysis because the tetrahedral and octahe...

Synthesis of a Ca(OH)2–carbon framework from crab shells and the polysulfide-trapping mechanisms of the modified separator for Li–S batteries.

The realization of a practical lithium sulfur battery system, despite its high theoretical specific capacity, is severely limited by fast capacity decay, which is mainly attributed to polysulfide dissolution and shuttle effect. To address this issue, we designed a thin cathode inactive material interlayer modified separator to block polysulfides. There are two advantages for this strategy. First, the coating material totally comes from the cathode, thus avoids the additional weights involved. Second, the cathode inactive material modified separator improve the reversible capacity and cycle performance by combining gelatin to chemically bond polysulfides and the carbon layer to physically block polysulfides. The research results confirm that with the cathode inactive material modified separator, the batteries retain a reversible capacity of 644 mAh g(-1) after 150 cycles, showing a low capacity decay of about 0.11% per circle at the rate of 0.5C.