Li-CO 2 batteries have attracted ever increasing attention due to their high energy and power densities. However, Li 2 CO 3 formed during the discharge process is difficult to decompose, leading to a large charge overpotential and poor cyclability. Thus, high-performance and low-cost catalysts that can be integrated into the electrode architecture are urgently needed for the development of practical Li-CO 2 batteries with a low overpotential and long cyclability. Herein, a high-performance composite catalyst is reported based on carbon quantum dots supported by holey graphene (CQD/hG), which, when used as the cathodic catalyst in a Li-CO 2 battery, can support the fast formation and decomposition of Li 2 CO 3 in organic electrolytes and achieve an overpotential as low as 1.02 V (Li/Li + ) at current density of 0.1 A g −1 . The discharge capacity of this Li-CO 2 battery is 12300 mAh g −1 under the current density of 0.5 A g −1 , showing an excellent long-term stability with up to 235 cycles even at a high current density of 1 A g −1 . The observed superb battery performance is attributable to synergistic effects that the CQD/hG composite architecture provides a high catalytic activity of the defect-rich CQDs and fast electron/electrolyte transport through the conducting holey graphene sheets.The ORCID identification number(s) for the author(s) of this article can be found under https://doi.org/10.1002/adfm.201804630. now facing. [1] Therefore, it is more important now than ever to develop renewable and clean energy technologies. [2] Although Li-ion batteries have been successfully commercialized as the clean energy source for consumer electronic devices, the low energy density of the stateof-the-art Li-ion batteries with the intrinsic Li + intercalation mechanism limited their use for energy-demanding applications, including electrical vehicles automobiles for long-distance transportation. [3] To address this issue, metal-air batteries with much higher energy and power densities than those of Li-ion batteries have attracted more and more interests. [4] For example, the Li/Na-O 2 batteries have been extensively studied and recently demonstrated with high energy densities and a long cycle life. [5] As a particular type of metalair batteries, Li-CO 2 batteries based on the redox reaction between the Li anode and CO 2 cathode (4Li + 3CO 2 = 2Li 2 CO 3 + C) [1b,6] can deliver ten times more energy density than that of a Li-ion battery. Furthermore, Li-CO 2 battery research is significant for the exploration missions on Mars, where CO 2 gas constitutes 96% of the atmosphere.A rechargeable Li-CO 2 battery using Ketjen Black (KB) as a cathodic catalyst was first reported in 2014, [7] which was cycled only for seven times with a limited discharge capacity of 1000 mAh g −1 due to a poor catalytic activity of the KB catalyst. This is because the main discharge product, Li 2 CO 3 , is a wide bandgap insulator with a sluggish kinetics for electrochemical decomposition during the charge process, leading to a high charge po...

Fundamental understanding of constructing elevated catalysts to realize fast electron transfer and rapid mass transport in oxygen reduction reaction (ORR) chemistry by interface regulation and structure design is important but still ambiguous. Herein, a novel jellyfish-like Mott-Schottkytype electrocatalyst is developed to realize fast electron transfer and decipher the structure-mass transport connection during ORR process. Both spectroscopy techniques and density functional theory calculation demonstrate electrons spontaneously transfer from Fe to N-doped graphited carbon at the heterojunction interface, thus accelerating electron transfer from electrode to reactant. Dynamic analysis indicates unique structure can significantly improve mass transport of oxygen-species due to two factors: one is electrolyte streaming effect caused by tentacle-like carbon nanotubes; the other is effective collision probability in the semiclosed cavity. Therefore, this Mott-Schottky-type catalyst delievers superior ORR performance with high onset potential, positive half wave potential, and large current density. It also exhibits low overpotential when serving as an air cathode in Zn-air batteries. This work deepens understanding of the two key factors-electron transfer and mass transport-on determining the kinetic reaction of ORR process and offers a new avenue in constructing efficient Mott-Schottky electrocatalysts.

No abstract

The electrocatalytic activity of Pt-based alloys exhibits a strong dependence on their electronic structures, but a relationship between electronic structure and oxygen reduction reaction (ORR) activity in Ag-based alloys is still not clear. Here, a vapor deposition based approach is reported for the preparation of Ag M (M = Cu, Co, Fe, and In) and Ag Cu (x = 0, 25, 45, 50, 55, 75, 90, and 100) nanocatalysts and their electronic structures are determined by valence band spectra. The relationship of the d-band center and ORR activity exhibits volcano-shape behaviors, where the maximum catalytic activity is obtained for Ag Cu alloys. The ORR enhancement of Ag Cu alloys originates from the 0.12 eV upshift in d-band center relative to pure Ag, which is different from the downshift in the d-band center in Pt-based alloys. The activity trend for these Ag M alloys is in the order of Ag Cu > Ag Fe > Ag Co . These results provide an insight to understand the activity and stability enhancement of Ag Cu and Ag Cu catalysts by alloying.