Single-atom metal-nitrogen-carbon (M-N-C) catalysts have sparked intense interests, but the catalytic contribution of N-bonding environment neighboring M-N sites lacks attention. Herein, a series of Fe-N-C nanoarchitectures have been prepared, which confer adjustable numbers of atomically dispersed Fe-N sites, tunable hierarchical micro-mesoporous structures and intensified exposure of interior active sites. The optimization between Fe-N single sites and carbon matrix delivers superior oxygen reduction reaction activity (half-wave potential of 0.915 V vs RHE in alkaline medium) with remarkable stability and high atom-utilization efficiency (almost 10-fold enhancement). Both experiments and theoretical calculations verified the selective C-N bond cleavage adjacent to Fe center induced by porosity engineering could form edge-hosted Fe-N moieties, and therefore lower the overall oxygen reduction reaction barriers comparing to intact atomic configuration. These findings provide a new pathway for the integrated engineering of geometric and electronic structures of single-atom materials to improve their catalytic performance.

As the bottleneck in photocatalytic water splitting, the oxygen evolution reaction (OER) has drawn huge attention, but its efficiency still falls short of expectations. A widely accepted speculation is that the catalytic activity of catalysts is insufficient (high reaction barriers). Herein, we develop a first-principles method to investigate the photocatalytic OER at the water/TiO2(110) interface. A full mechanism uncovering the importance of radicals is determined. Kinetic analysis further enables us to quantitatively estimate each possible obstacle in the process. We demonstrate unambiguously that the rate-determining factor of OER varies with the concentration of surface-reaching photoholes (Ch+). Under experimental conditions, the intrinsic catalytic activity of TiO2(110) dose not represent the major obstacle, but all steps involving photoholes are slow due to their low concentrations. It suggests that the key to enhance the OER efficiency at the current stage (before approaching the estimated threshold Ch+ = ~10-4) is to increase Ch+.

The low-cost room-temperature sodium-sulfur battery system is arousing extensive interest owing to its promise for large-scale applications. Although significant efforts have been made, resolving low sulfur reaction activity and severe polysulfide dissolution remains challenging. Here, a sulfur host comprised of atomic cobalt-decorated hollow carbon nanospheres is synthesized to enhance sulfur reactivity and to electrocatalytically reduce polysulfide into the final product, sodium sulfide. The constructed sulfur cathode delivers an initial reversible capacity of 1081 mA h g−1 with 64.7% sulfur utilization rate; significantly, the cell retained a high reversible capacity of 508 mA h g−1 at 100 mA g−1 after 600 cycles. An excellent rate capability is achieved with an average capacity of 220.3 mA h g−1 at the high current density of 5 A g−1. Moreover, the electrocatalytic effects of atomic cobalt are clearly evidenced by operando Raman spectroscopy, synchrotron X-ray diffraction, and density functional theory.

Room‐temperature sodium–sulfur (RT‐Na/S) batteries hold significant promise for large‐scale application because of low cost of both sodium and sulfur. However, the dissolution of polysulfides into the electrolyte limits practical application. Now, the design and testing of a new class of sulfur hosts as transition‐metal (Fe, Cu, and Ni) nanoclusters (ca. 1.2 nm) wreathed on hollow carbon nanospheres (S@M‐HC) for RT‐Na/S batteries is reported. A chemical couple between the metal nanoclusters and sulfur is hypothesized to assist in immobilization of sulfur and to enhance conductivity and activity. S@Fe‐HC exhibited an unprecedented reversible capacity of 394 mAh g−1 despite 1000 cycles at 100 mA g−1, together with a rate capability of 220 mAh g−1 at a high current density of 5 A g−1. DFT calculations underscore that these metal nanoclusters serve as electrocatalysts to rapidly reduce Na2S4 into short‐chain sulfides and thereby obviate the shuttle effect.

First principles calculations with molecular dynamics are utilized to simulate a simplified electrical double layer formed in the active electric potential region during the electrocatalytic oxidation of ethanol on Pd electrodes running in an alkaline electrolyte. Our simulations provide an atomic level insight into how ethanol oxidation occurs in fuel cells: New mechanisms in the presence of the simplified electrical double layer are found to be different from the traditional ones; through concerted-like dehydrogenation paths, both acetaldehyde and acetate are produced in such a way as to avoid a variety of intermediates, which is consistent with the experimental data obtained from in situ FTIR spectroscopy. Our work shows that adsorbed OH on the Pd electrode rather than Pd atoms is the active center for the reactions; the dissociation of the C−H bond is facilitated by the adsorption of an OH − anion on the surface, resulting in the formation of water. Our calculations demonstrate that water dissociation rather than H desorption is the main channel through which electrical current is generated on the Pd electrode. The effects of the inner Helmholtz layer and the outer Helmholtz layer are decoupled, with only the inner Helmholtz layer being found to have a significant impact on the mechanistics of the reaction. Our results provide atomic level insight into the significance of the simplified electrical double layer in electrocatalysis, which may be of general importance.

Controversial results still exist about the activities of tetrahedral (Co2+) and octahedral (Co3+) sites in Co3O4 toward the OER. Theoretical and experimental data confirm that octahedral sites are responsible for the OER, using model catalysts.

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The enhancement of electron-and-hole separation efficiency and facile generation of reactive oxygen species are significant factors for performance improvement of photocatalysts in selective toluene photocatalytic oxidation. Heterojunction and defect construction have been regarded as valid methods to boost photocatalytic activity of semiconductors. Herein, the CdIn2S4-CdS composite with compact heterojunctions and defect-induced sulfur vacancies was fabricated by a one-step hydrothermal process. The sheet-to-sheet heterojunctions and the abundant sulfur vacancies facilitate separation and migration of photoinduced charge carriers. Benefited from the compositional and structural synergy, the prepared CdIn2S4-CdS-140 composite boosted photocatalytic oxidation activity for toluene conversion into benzaldehyde (remarkable toluene conversion of 80.3% and benzaldehyde selectivity of 99% in 6 h) under visible light irradiation. It is noteworthy that the composite can perform well when pure O2 was replaced with air.