NSRRC Activity Report 2022

024 NSRRC ACTIVITY REPORT 2022 using GC-MS. The discrepancy with previous reports could be attributed to the trace amounts of O 2 and/or H 2 O that participated in the reduction reaction. O 2 and H 2 O themselves could be reduced at approximately 3 V vs. Li/Li + and could act as electrocatalysts to promote CO 2 reduction. Combining the theoretical calculations and experimental results, they proposed that pure CO 2 could not be reduced to C at potentials above 2 V. In summary, a suitable electrocatalyst is required to improve the discharge overpotential. Efforts should be devoted to the development of electrocatalysts that ease the charge- transfer reactions. From this point of view, O 2 and H 2 O could be good candidates as electrocatalysts, owing to their capability to increase the partial positive charge on C in CO 2 . However, as Li metal is highly reactive to both O 2 and H 2 O, electrocatalysts with good stability with respect to the highly reductive Li should be developed. sXAS plays an important role in revealing the chemical states of the reactants in Li-CO 2 batteries. In the future, an in situ sXAS setup would further benefit the mechanism study. (Reported by Kevin Iputera, National Taiwan University) This report features the work of Ru-Shi Liu and his collaborators published in J. Mater. Chem. A 10 , 3460 (2022). TLS 20A1 XAS • sXAS • CO 2 Reduction, Li-CO 2 Battery, Electrocatalyst, Chemistry Reference 1. K. Iputera, J. Y. Huang, S. C. Haw, J. M. Chen, S. F. Hu, R. S. Liu, J. Mater. Chem. A 10 , 3460 (2022). Adding a Protective Layer for Aqueous Zinc Ion Capacitors A mechanism study of zinc dendrite suppression used in situ transmission X-ray microscopy. A queous zinc-ion capacitors (ZIC) have recently attracted attention as promising energy-storage devices for portable electronics and large-scale energy-storage systems, owing to their low cost, high stability, high safety, high power, and high energy density. 1 A ZIC comprises a battery-type Zn metal anode (prepared by Zn plating and stripping) and a supercapacitor-type cathode (that provides a high double-layer capacitance or pseudocapacitance), as illustrated in Fig. 1(a) . Supercapacitor-type cathode materials are usually high-surface-area carbons, e.g. , activated carbon, 3 graphene, 4 carbon nanotubes, 5 and mesoporous carbon. 6 Graphene exhibits a double-layer capacitance among these carbon materials, owing to its high theoretical surface area (2630 m 2 g −1 ) and high electrical conductivity. 7 In addition, carbon materials with porous structures exhibit a high surface area and porosity, which can facilitate ion diffusion and the accumulation of a considerable number of charges, enhancing the double-layer capacitance. 8 A Zn foil anode is promising for mass production because of its low cost and high theoretical capacity (820 mAh g −1 ). 1 However, the main challenge concerns the formation of Zn dendrite on the anode, which results in short circuits and capacity decay. Different approaches have been employed to suppress the dendrite formation on the anode, such as using a three-dimensional Zn structure, ion distributors, and artificial solid electrolyte interphase as protection layers. 9 Wei-Hsiang Lin, Han-Yi Chen (National Tsing Hua University), Chia-Liang Sun (Chang Gung University), Ming-Hsien Lin (National Defense University), Chun- Chieh Wang (NSRRC), and their research teams have proposed the use of a high-surface-area nanoporous core–shell-structured multiwalled carbon nanotube@ graphene oxide nanoribbon (NP-MWCNT@GONR), which is prepared by using a facile microwave- assisted method as illustrated in Fig. 1(b) , as the cathode material and protection layer in aqueous ZICs. 10 The MWCNTs in the core–shell structure inhibit the restacking of the graphene layers, which can significantly enhance the cycling stability. In addition, MWCNTs possess high electronic conductivity, which Fig. 1 : (a) Schematic of the NP-MWCNT@GONR//Zn(CF 3 SO 3 ) 2 //Zn. (a)