Highly selective CO₂ conversion to methane or syngas tuned by CNTs@non-noble–metal cathodes in Zn–CO₂ flow batteries

Abstract

Metal-CO2 batteries represent a potential new environmental protection technology, which can effectively reduce CO2 emissions while ensuring energy output. However, the design of active, selective, and cost-efficient electrocatalyst remains a...

Functional Aqueous Zinc–Acetylene Batteries for Electricity Generation and Electrochemical Acetylene Reduction to Ethylene

“…The as‐designed Zn–C 2 H 2 battery under a pure acetylene stream exhibits a very large open circuit potential of 1.14 V, a high power density of up to 2.2 mW cm −2 , and an energy density of 213.8 Wh kg Zn −1 , which are much higher than those for reported Zn–CO 2 batteries [18, 22–34] . Even under a crude ethylene stream containing 1 vol.…”

“…Even at a large current density of 14 mA cm −2 , the ethylene FE in the Zn–C 2 H 2 battery was still as high as 95.4 %. In contrast, current Zn–CO 2 batteries can only operate at low current densities of <10 mA cm −2 [19–34] . Furthermore, no ethane was detected, indicating that the overhydrogenation reaction of ethylene was effectively suppressed.…”

“…[29] Markedly, the Zn-C 2 H 2 battery generated a stable open circuit potential of 1.14 V (Figure 1c), which was much larger than those for currently reported Zn-CO 2 batteries, for example 0.6 V for s-SnLi, [27] 0.79 V for cedar biomassderived N-doped graphitized carbon (CB-NGC-2), [33] and 0.82 V for carbon nanotubes directly grown on copper mesh (CNTs@Cu). [31] According to the mass change of the Zn anode before and after the discharge process at 6.0 mA cm À 2 , the specific capacity of the Zn-C 2 H 2 battery was calculated to be � 786 mAh g Zn À 1 (Figure 1d), corresponding to an energy density of 213.8 Wh kg Zn . In order to further investigate electricity-generating practicability, two Zn-C 2 H 2 batteries were connected in series and achieved a stable cell voltage output of 2.33 V. Subsequently, a light-emitting diode (nominal voltage: 2.0-2.2 V) was successfully powered (Figure 1e and S11, S12), indicating the practical feasibility of the Zn-C 2 H 2 batteries.…”

“…In contrast, current Zn-CO 2 batteries can only operate at low current densities of < 10 mA cm À 2 . [19][20][21][22][23][24][25][26][27][28][29][30][31][32][33][34] Furthermore, no ethane was detected, indicating that the overhydrogenation reaction of ethylene was effectively suppressed. As the discharge current density increased, the production rate of ethylene significantly increased to 5.8 mL cm À 2 h À 1 at 14 mA cm À 2 (Figure 2b).…”

“…The as-designed Zn-C 2 H 2 battery under a pure acetylene stream exhibits a very large open circuit potential of 1.14 V, a high power density of up to 2.2 mW cm À 2 , and an energy density of 213.8 Wh kg Zn À 1 , which are much higher than those for reported Zn-CO 2 batteries. [18,[22][23][24][25][26][27][28][29][30][31][32][33][34] Even under a crude ethylene stream containing 1 vol. % acetylene impurities, the Zn-C 2 H 2 battery still exhibited an acetylene conversion of 99.97 %, an ethylene specific selectivity of 95 %, and eventually produced a polymer-grade ethylene feed with only � 3 ppm acetylene over a long-term discharge process.…”