Enhanced electrodeposition and separation of metallic Cr from soluble K2CrO4 on a liquid Zn cathode

Electrochemical Fixation of Carbon Dioxide in Molten Salts on Liquid Zinc Cathode to Zinc@Graphitic Carbon Spheres for Enhanced Energy Storage

“…The interplanar distances of 3.4 Å in the shell and 2.1 Å in the core in the high-resolution TEM image ( Figure 2h) are ascribed to the crystal planes of graphitic carbon (002) and Zn (101). [22,35,36] The elements distributions also validate the core-shell Zn@C structure, as confirmed by the separated location of Zn in the core (Figure 2i-k) and carbon in the shell (Figure 2i,j,l). The obtained core-shell Zn@C features a specific surface area of 160 m 3 g −1 and a pore size centered at 4 nm ( Figure S1, Supporting Information).…”

“…Potentiostatic electrolysis was conducted at −0.9 V versus Ag/Ag 2 SO 4 for 3 h in the Li 2 CO 3 –Na 2 CO 3 –K 2 CO 3 molten salt at 450 °C, with the liquid Zn as the working electrode (cathode) and a platinum‐coated titanium plate as the counter electrode (anode). The X‐ray diffraction (XRD) pattern (red line in Figure 2 a), Raman spectrum (red line in Figure 2b and inset in Figure 2b), and X‐ray photoelectron spectrometer (XPS) spectra (see Zn 2p spectrum in the left side and C ls spectrum in the right side of Figure 2c) all prove the coexistence of Zn and C in the cathodic Zn@C. [ 22,35,36 ] In Figure 2a, the broad peak located at 23° is ascribed to the (002) crystal plane of graphitized carbon (JCPDS No. 01‐0646).…”

“…In contrast to the solid Mo electrode (black dotted line in Figure 3n), the liquid Zn cathode can enable the reduction of CO 2 ‐capture‐generated CO 3 2− with a lower overpotential (that is, more positive reduction potential indicated by the red line in Figure 3n), suggesting that the liquid Zn can act as a depolarizer to facilitate the electrochemical fixation of CO 2 . [ 2,35,39 ] Moreover, the liquid Zn cathode shows a larger current density for the electrochemical reduction of CO 3 2− over the solid Mo electrode (Figure 3n), revealing that liquid Zn droplets can also enhance the reaction kinetics by increasing the Zn–molten salt interfacial area. [ 2,35,40 ] Furthermore, the flowable liquid Zn can contribute to the real‐time update of the reaction interfaces, also resulting in improved reaction kinetics.…”

“…[6,[17][18][19]48,[51][52][53][54] Figure 4c), which are extruded and separated from the carbon flakes due to the surface tension and insolubility of Zn in carbon at 450 °C ( Figure S5, Supporting Information). [2,35,39,42] Finally, carbon deposition by electrochemical reduction of CO 2capture-generated CO 3 2− (CO 3 2− + 4e − = C(s) + 3O 2− , reaction 3 in Figure 4c) on the surface of liquid Zn droplets results in the core-shell structured Zn@C spheres. The Zn core can catalyze the graphitization of the carbon shell in the Zn@C spheres.…”

“…A fast reduction process can hopefully be realized by using liquid metals as cathodes because liquid metals can not only act as the depolarizer via the alloying effect, but also enhance the mass transfer on the electrolyte-electrode interfaces due to the flowable characteristics. [34,35] Nevertheless, using the liquid metals as cathodes for the electrochemical fixation of CO 2 in molten salts still remains to be explored. Herein, a liquid zinc cathode is introduced to the electrochemical fixation of CO 2 in molten salts, to simultaneously accelerate CO 2 conversion and enhance the functionality of derived materials.…”