Wearable solid-state ZAB properties
Since the sample FeN?-Ti?C?S? exhibited high ORR activity, the article further used the developed FeN?-Ti?C?S? catalysts with alkali-resistant dual-network PANa and cellulose hydrogel (PANa-cellulose ) as stretchable solid electrolytes to jointly construct a stretchable and abrasion-resistant fibrous ZAB.Fig. 4a illustrates that it can be stretched over 1000% strain without any fracture and visible cracks, with excellent tensile properties. The structure of the fibrous ZAB is shown in Fig. 4 b. A hydrogel electrolyte was used to first wrap the Zn spring electrode, then stretch it, and finally wrap the FeN?-Ti?C?S?-loaded carbon paper as the air electrode. The charging and discharging curves and corresponding power densities of the fibrous ZAB in the initial and 800% stretched states are shown in Fig. 4c, d. The maximum power density of the ZAB in the initial state is 133.6 mW-cm-?, and that of the ZAB in the stretched state at 800 ℃ is 182.3 mW-cm-?. indicating that the cell is stretchable and has good electrochemical performance in the stretched state. In addition, the cell exhibits excellent cycling stability with a stable cycling of 110 h at 2 mA cm-?, as shown in Fig. 4e. To demonstrate its wear resistance, two fiber-shaped ZABs with a length of 10 cm and a diameter of 2 mm were woven into a wristband and attached to a glove as shown in Fig. 4f and g. The wristband was made of a fiber-shaped ZAB with a diameter of 2 mm. This wristband can power a set of LEDs on the wearing gloves, demonstrating the feasibility of this highly efficient stretchable and wearable fiber-shaped ZAB based on the prepared FeN?-Ti?C?S? catalyst.
Tensile stress versus strain curves of the prepared PANa-cellulose hydrogel, and the inset shows optical photographs of this hydrogel electrolyte in the initial and stretched states; (b) schematic diagram of the stretchable fibrous ZAB; (c) charge-discharge curves of the fibrous ZAB in the initial and 800% stretched states; (d) discharge and power density curves of the fibrous ZAB in the initial and 800% stretched states ; (e) cycling stability test of fiber-shaped ZABs at 2 mA cm-?; (f) photographs of two fiber-shaped ZABs (length: 10 cm, diameter: 2 mm) woven into a wristband; (g) photographs of this wristband attached to a glove; (h) photographs of this wristband attached to a glove to supply power to a set of LEDs
Source of ORR electrocatalytic activity
In the article, the energy band structures of FeN?-Ti?C? and FeN?-Ti?C?S? samples were investigated using UPS. As shown in Fig. 5a, the cutoff energy of FeN?-Ti?C? is 17.1 and that of FeN?-Ti?C?S? is 17.23. Further estimation of the figure of merit function (Φ) and valence band maxima (EV) reveals that, compared with FeN?- Ti?C? compared to FeN?-Ti?C?S? the reduction of Φ and EV shifts to lower energies, indicating that the addition of the S-terminal to the Ti?C? carrier results in the spatial stabilization of the electrons within the FeN? part, and a change of the center of the 3d band of energy of Fe(II) . In addition, the corresponding effective magnetic moments (?) shown in Fig. 5c indicate that the ? effect for sample FeN?-Ti?C?S? is larger than that for sample FeN?-Ti?C?, and that the large ? effect suggests that the number of unpaired d electrons is greater for Fe(II) in the sample. In addition, DFT calculations show that the introduction of the S-terminus can increase the in situ magnetic moment of the Fe center and modulate the spin state of Fe(II) in the FeN? fraction (the intermediate spin state is transformed into the high spin state), resulting in the Fe 3d electron delocalization and upward shifting of the d-band centers thereby optimizing the orbital hybridization of Fe 3d with the p orbitals of oxygen-containing moieties, which can enhance the molecular oxygen adsorption, indicating that the FeN?-Ti?C?S? system has a good catalytic activity for ORR, which is in good agreement with the experimental results.
