However, the development of Li-S batteries is still facing many challenges, mainly including the insulating properties of S/Li 2 S 2 /Li 2 S, the huge volume changes during cycles as well as the dissolution and shuttle of lithium polysulfides (LiPSs) in the electrolyte. Additionally, the complex multi-electron and multi-phase reactions of sulfur species cause sluggish redox kinetics, which severely limits the battery performance. [2] Furthermore, for the purpose of taking full advantages of high-energy-density of Li-S batteries in practical applications, high sulfur loadings and low amount of electrolyte are necessary. It further increases the electrochemical polarization and aggravates the loss of LiPSs, leading to the inferior cycling stability and low specific capacity. [3] Nowadays, many researches concentrate on the design and optimization of sulfur host to solve the above problems. [4] Carbon materials and metal compounds are generally combined as the sulfur host to construct channels for transferring electrons and ions, adsorb LiPSs and catalyze the conversions of LiPSs. [5] Among the metal compounds, transition metal phosphides (TMPs) have drawn increasing interests because of their excellent electronic conductivity, easily adjustable electronic structure and high catalytic activity. [6] Some studies have shown that TMPs can chemically immobilize LiPSs through M-S and PLi bonds to restrain the shuttle effect and expedite redox kinetics in electrochemical conversions of LiPSs. Chen et al. found that CoP nanoparticles can effectively capture LiPSs and reduce the overpotential of Li 2 S nucleation. [7] Wang et al. demonstrated that MoP nanoparticles can inhibit the formation of "dead sulfur" under lean electrolyte conditions. [8] Qian et al. revealed the best catalytic behavior of CoP among several cobalt-based metal compounds (Co 3 O 4 , CoS 2 , Co 4 N, and CoP). [9] Although some progress has been made in the application of TMPs in Li-S batteries, it is still a challenge to further restrain the shuttle effect and improve the electrochemical kinetics through regulating its electronic structures.Since defect engineering has been shown to effectively tailor the electronic structure of metal compounds, the possibility of tuning the adsorption and electrochemical conversions of LiPSs on the surface of sulfur hosts through anion vacancy Lithium-sulfur batteries have aroused great interest in the context of rechargeable batteries, while the shuttle effect and sluggish conversion kinetics severely handicap their development. Defect engineering, which can adjust the electronic structures of electrocatalyst, and thus affect the surface adsorption and catalytic process, has been recognized as a good strategy to solve the above problems. However, research on phosphorus vacancies has been rarely reported, and how phosphorus vacancies affect battery performance remains unclear. Herein, CoP with phosphorus vacancies (CoP-Vp) is fabricated to study the enhancement mechanism of phosphorus vacancies in Li-S chemistry...

Defective materials have been demonstrated to possess adsorptive and catalytic properties in lithium–sulfur (Li–S) batteries, which can effectively solve the problems of lithium polysulfides (LiPSs) shuttle and sluggish conversion kinetics during charging and discharging of Li–S batteries. However, there is still a lack of research on the quantitative relationship between the defect concentration and the adsorptive‐catalytic performance of the electrode. In this work, perovskites Sr0.9Ti1−xMnxO3−δ (STMnx) (x = 0.1–0.3) with different oxygen‐vacancy concentrations are quantitatively regulated as research models. Through a series of tests of the adsorptive property and electrochemical performance, a quantitative relationship between oxygen‐vacancy concentration and adsorptive‐catalytic properties is established. Furthermore, the catalytic mechanism of oxygen vacancies in Li–S batteries is investigated using density functional theory calculations and in situ experiments. The increased oxygen vacancies can effectively increase the binding energy between perovskite and LiPSs, reduce the energy barrier of LiPSs decomposition reaction, and promote LiPSs conversion reaction kinetics. Therefore, the perovskite STMn0.3 with high oxygen‐vacancy concentrations exhibits excellent LiPSs adsorptive and catalytic properties, realizing high‐efficiency Li–S batteries. This work is helpful to realize the application of the quantitative regulation strategy of defect engineering in Li–S batteries.

Hydrodesulfurization (HDS) is one of the most efficient methods to remove harmful sulfur from oil to produce clean hydrocarbons. Molybdenum sulfide (MoS2) has been used extensively for HDS for several decades, which can be further improved toward more effective catalysts due to its distinctive phase-engineering nature. Here, 1T-2H mixed-phase MoS2 nanoflowers with tunable defects have been synthesized and used in the HDS reaction. A facile solvothermal method involving water, ethanol, and glycerin has been developed for generating stable mixed 1T-2H MoS2 in which the vacancies of both S and Mo have been produced. Detailed characterizations based on transmission electron microscopy, X-ray photoelectron spectra, Raman, and electron paramagnetic resonance show that the 1T/2H ratio and vacancies of MoS2 have been effectively tuned by changing the composition of solvothermal solvent. Temperature-programmed reduction results show greatly affected H2 adsorption behavior of MoS2 by engineering of the phases and defects. In the HDS of dibenzothiophene, stable defect-rich mixed 1T-2H MoS2 with high activity and high hydrogenation selectivity was obtained via the accurately controlled solvothermal environment of water, ethanol, and glycerin. The used catalyst still maintains high performance, which is attributed to the retained mixed 1T-2H phases and the dual defects in the harsh reaction environment.

Reversible solid oxide cells (RSOCs) present a conceivable potential for addressing energy storage and conversion issues through realizing efficient cycles between fuels and electricity based on the reversible operation of the fuel cell (FC) mode and electrolysis cell (EC) mode. Reliable electrode materials with high electrochemical catalytic activity and sufficient durability are imperatively desired to stretch the talents of RSOCs. Herein, oxygen vacancy engineering is successfully implemented on the Fe-based layered perovskite by introducing Zr4+, which is demonstrated to greatly improve the pristine intrinsic performance, and a novel efficient and durable oxygen electrode material is synthesized. The substitution of Zr at the Fe site of PrBaFe2O5+δ (PBF) enables enlarging the lattice free volume and generating more oxygen vacancies. Simultaneously, the target material delivers more rapid oxygen surface exchange coefficients and bulk diffusion coefficients. The performance of both the FC mode and EC mode is greatly enhanced, exhibiting an FC peak power density (PPD) of 1.26 W cm–2 and an electrolysis current density of 2.21 A cm–2 of single button cells at 700 °C, respectively. The reversible operation is carried out for 70 h under representative conditions, that is, in air and 50% H2O + 50% H2 fuel. Eventually, the optimized material (PBFZr), mixed with Gd0.1Ce0.9O2, is applied as the composite oxygen electrode for the reversible tubular cell and presents excellent performance, achieving 4W and 5.8 A at 750 °C and the corresponding PPDs of 140 and 200 mW cm–2 at 700 and 750 °C, respectively. The enhanced performance verifies that PBFZr is a promising oxygen electrode material for the tubular RSOCs.

For developing the reversible lithium metal anode, constructing an ideal solid electrolyte interphase (SEI) by regulating the Li + solvation structure is a powerful way to overcome the major obstacles of lithium dendrite and limited Coulombic efficiency (CE). Herein, spherical mesoporous molecular sieve MCM-41 nanoparticles are coated on a commercial PP separator and used to regulate the Li + solvation structure for lithium metal batteries (LMBs). The regulated solvation structure exhibits an agminated state with more contact ion pairs (CIPs) and ionic aggregates (AGGs), which successfully construct a homogeneous inorganic-rich SEI in the lithium anode. Meanwhile, the regulated solvation structure weakens the interaction between the solvents and Li + , resulting in low Li + desolvation energy and uniform Li deposition. Thus, a high CE (∼96.76%), dendrite-free Li anode, and stable Li plating/stripping cycling for approximately 1000 h are achieved in the regulated carbonate-based electrolyte without any additives. Therefore, regulating the Li + solvation structure in the electrolyte by employing a mesoporous material is a forceful way to construct an ideal SEI and harness lithium metal.