The sulfur redox kinetics critically matters to superior lithium-sulfur (Li-S) batteries, for which single atom catalysts (SACs) take effect on promoting Li 2 S redox process and mitigating the shuttle behavior of lithium polysulfide (LiPs). However, conventional trial-and-error strategy significantly slows down the development of SACs in Li-S batteries. Here, the Li 2 S oxidation processes over MN 4 @G catalysts are fully explored and energy barrier of Li 2 S decomposition (E b ) is identified to correlate strongly with three parameters of energy difference between initial and final states of Li 2 S decomposition, reaction energy of Li 2 S oxidation and Li-S bond strength. These three parameters can serve as efficient descriptors by which two excellent SACs of MoN 4 @G and WN 4 @G are screened which give rise to E b values of 0.58 and 0.55 eV, respectively, outperforming other analogues in adsorbing LiPs and accelerating the redox kinetics of Li 2 S. This method can be extended to a wider range of SACs by coupling MN 4 moiety with heterostructures and heteroatoms beyond N where WN 4 @G/TiS 2 heterointerface is predicted to exhibit enhanced catalytic performance for Li 2 S decomposition with E b of 0.40 eV. This work will help accelerate the process of designing a wider range of efficient catalysts in Li-S batteries and even beyond, e.g. alkali-ion-Chalcogen batteries.

Reported herein is an active and durable CoN‐containing oxygen evolution reaction (OER) electrocatalyst which efficiently functions in a neutral medium (pH ≈7). The composite material (N, S)‐RGO@CoN is synthesized by delicate atomic layer deposition (ALD) of CoN on a nitrogen and sulfur (N, S) co‐doped reduced graphene oxide (RGO) substrate. Representative results of the comprehensive study are: 1) The flower‐like sphere RGO substrate prepared by spray drying method features rich physical and chemical properties, which are beneficial for rapid mass/charge transfer to improve the intrinsic OER process; 2) the optimal ALD material for OER tests is afforded by tuning spray conditions and ALD parameters. Versatile structural and compositional characterizations confirm uniform growth and strong chemical coupling of nanostructured CoN on (N, S)‐RGO matrix; 3) the material is electrocatalytically active and durable in a neutral electrolyte, recording an OER overpotential of 220 mV at a current density of 10 mA cm−2 and stability of 20 h continuous catalysis at 20 mA cm−2 with nearly 100% Faradic efficiency; 4) Upon the experimental studies and density functional theory calculations, the eventual mechanism of remarkable OER activity conforms to the structural fate of ALD CoN electronic coupling to the carbon substrate.

oxides (rGO), [4] with various heteroatoms doping, including B, N, P, O, S, and Se elements. [2c,5] Among them, N-doping is the most extensively studied regulation strategy so that the N-doping mechanism has been widely accepted for understanding the origin of the enhanced ORR performance of CMFCs. [2b,d,5a,d] Nevertheless, the research of CMFCs toward ORR slows down and even is stuck because for more than one decade the performance discrepancy of CMFCs: worse ORR performance in acidic solution than in alkaline medium, critically hampering them from commercial applications in acid fuel cells. [6] Hence, unraveling the origin of the performance discrepancy is pivotal to address this challenge.The origin of the ORR performance discrepancy between acidic and alkaline solutions may be led by the unsatisfied performance of the "active sites" for trapping O 2 molecule because the O 2 adsorption is essential to initiate acidic ORR while in alkaline medium O 2 could be reduced directly into adsorbed OOH. [7] Therefore, to identify the active sites and elucidate the mechanism of performance discrepancy of CMFCs between acidic and alkaline solutions, the key aspect ought to be searching for the active sites possessing low overpotentials and weak O 2 binding strength, by which the structural insight will consequently facilitate the materials design of metal-free catalysts for acidic ORR. Almost all of the previous works assigned the acidic ORR performance of CMFCs to the active sites locating near the edges, such as the zigzag edges, [8] edge pentagons [9] and edge carbons near the dopants. [10] Nevertheless, such findings still shed no lights on the origin of the worse ORR performance of CMFCs in acidic solution than that in alkaline solution. This is because zigzag edges exhibit both relatively low overpotenials and strong capturing capability to O 2 molecule, [8,11] indicating that those edge sites exhibit similar ORR performance in both acidic and alkaline solutions. Therefore, to unravel the origin of the poor ORR performance of CMFCs in acidic solution, the research attention should be shifted from the edges to the basal plane. However, no research has been performed to investigate the ORR performance of the basal-plane sites in CMFCs due to the limited understanding of the structure-property correlations.Oxygen atoms sitting in the sp 2 lattice featuring with COC and CO have been confirmed experimentally [12] Carbon-based metal free catalysts (CMFCs) are far away from commercial availability mainly attributed to their poor oxygen reduction reaction (ORR) performance in acidic environment with the causes remaining obscure. By investigating the heteroatoms (N, B, P, S, Se, and Te)-doped reduced graphene oxides, the degradation mechanism of acidic ORR performance of CMFCs is found to be correlated with the oxygen-baring defects in the carbon sp 2 lattice, which exhibit overpotentials as low as 0.44 V but weak trapping capabilities for oxygen molecules. These findings not only revise the previously reported strate...

Atomically dispersed M–N–C has been considered an effective catalyst for various electrochemical reactions such as oxygen reduction reaction (ORR) and oxygen evolution reaction (OER), which faces the challenge of increasing metal load while simultaneously maintaining catalytic performance. Herein, we put forward a strategy for boosting catalytic performances of a single Cu atom coordinated with three N atoms (CuN 3 ) for both ORR and OER by increasing the density of connected CuN 3 moieties. Our calculations first show that a single CuN 3 moiety exhibiting no catalytic performance for ORR and OER can be activated by increasing the density of metal centers, which weakens the binding affinity to *OH due to the lowered d-band center of the metal atoms. These findings stimulate the further theoretical design of a two-dimensional compound of C 3 N 3 Cu with a high concentration of homogeneously distributed CuN 3 moieties serving as bifunctional active sites, which demonstrates efficient catalytic performance for both ORR and OER as reflected by the overpotentials of 0.71 and 0.43 V, respectively. This work opens a new avenue for designing effective single-atom catalysts with potential applications as energy storage and conversion devices possessing high density of metal centers independent of the doping strategy and defect engineering, which deserves experimental investigation in the future.

Lithium sulfur battery is one of the most promising applicants for the next generation of energy storage devices whose commercial applications are impeded by the key issue of shuttle effect....