Revealing the Selective Bifunctional Electrocatalytic Sites via In Situ Irradiated X‐Ray Photoelectron Spectroscopy for Lithium–Sulfur Battery

Abstract

The electrocatalysts are widely applied in lithium-sulfur (Li-S) batteries to selectively accelerate the redox kinetics behavior of Li 2 S, in which bifunctional active sites are established, thereby improving the electrochemical performance of the battery. Considering that the Li-S battery is a complex closed "black box" system, the internal redox reaction routes and active sites cannot be directly observed and monitored especially due to the distribution of potential active-site structures and their dynamic reconstruction. Empirical evidence demonstrates that traditional electrochemical test methods and theoretical calculations only probe the net result of multi-factors on an average and whole scale. Herein, based on the amorphous TiO 2-x @Ni selective bifunctional model catalyst, these limitations are overcome by developing a system that couples the light field and in situ irradiated X-ray photoelectron spectroscopy to synergistically convert the "black box" battery into a "see-through" battery for direct observation of the charge transportation, thus revealing that amorphous TiO 2-x and Ni nanoparticle as the oxidation and reduction sites selectively promote the decomposition and nucleation of Li 2 S, respectively. This work provides a universal method to achieve a deeper mechanistic understanding of bidirectional sulfur electrochemistry.

Field‐assisted electrocatalysts spark sulfur redox kinetics: From fundamentals to applications

“…[ 26 ] As a result, the cathode with CdS‐TiO 2 /CC under light illumination shows an ultrahigh initial specific capacity of more than 1500 mAh/g and reversibly remains at 1225 mAh/g after approximately 50 cycles, which is superior to the counterpart without light irradiation. Very recently, in‐situ irradiated X‐ray photoelectron spectroscopy is developed to intuitively observe the transfer routes of photogenerated electrons and holes inside heterogeneous electrocatalytic pair sites in Li–S electrocatalysis, which was first reported by Zhang et al [ 131 ]…”

“…[26] As a result, the cathode with CdS-TiO 2 /CC under light illumination shows an ultrahigh initial specific capacity of more than 1500 mAh/g and reversibly remains at 1225 mAh/g after approximately 50 cycles, which is superior to the counterpart without light irradiation. Very recently, in-situ irradiated X-ray photoelectron spectroscopy is developed to intuitively observe the transfer routes of photogenerated electrons and holes inside heterogeneous electrocatalytic pair sites in Li-S electrocatalysis, which was first reported by Zhang et al [131] In contrast, there is a lack of separation of electrons and holes in the discharge process without photoassistance. If the VB of the electrocatalysts is lower than the LUMO of LiPSs, the driving force stemming from the F I G U R E 5 (A) Schematic illustration of charge transfer between LiPSs and electrocatalysts with different energy band configurations.…”

A Separator with Double Coatings of Li4Ti5O12and Conductive Carbon for Li‐S Battery of Good Electrochemical Performance

“…In addition, the advantages of sulfur, which has low cost, is easily available, and environmentally friendly, have also attracted wide attentions. [5][6][7][8] However, The 'shuttle effect' and lithium anode corrosion have always restricted the development of Li-S batteries. During the charging and discharging process, the soluble lithium polysulfides (Li 2 S x , 2 < x ≤ 8) are formed and dissolved in the electrolyte, resulting in the loss of active sulfur and corrosion of lithium anodes, which leads to the sharp capacity decline and poor safety performance.…”

Revealing Photocatalytic Performance of ZnxCd1–xS Nanoparticles Depending on the Irradiation Wavelength

“…Herein, we used HMF to evaluate the photocatalytic activity of Zn x Cd 1– x S NPs. In addition, we performed in situ X-ray photoelectron spectroscopy (XPS) measurements to investigate their wavelength-dependent photocatalytic activity. , The surface structure and morphology of the Zn x Cd 1– x S NPs were analyzed using powder X-ray diffraction (XRD), high-resolution transmission electron microscopy (HRTEM), energy-dispersive X-ray spectroscopy (EDX), UV–vis diffuse reflectance (DR) spectroscopy, and Raman spectroscopy. The photocatalytic degradation (PCD) reaction of HMF using Zn x Cd 1– x S NPs varied significantly with wavelength.…”