Using high-efficiency and low-cost catalyst to replace noble metal platinum for electrocatalytic hydrogen evolution reaction (HER) provides a broad prospect for the development of renewable energy technology, which is an important task yet to be solved. Herein, we proposed an efficient doping–adsorption–pyrolysis strategy for constructing a robust coupling catalyst composed of single-atom Co–N3 sites anchored on an N-doped carbon (N–C) layer and encapsulated Co nanocrystals (NCs) to activate the interfacial water for accelerating HER. Beneficial to the strong synergistic effect of Co–N3 sites and Co NCs, the optimized CoNC‑SA/N*–C catalyst showed excellent HER activity and stability in both acidic and alkaline electrolytes. In situ attenuated total reflectance–surface-enhanced infrared absorption spectroscopy revealed that the rigid interfacial water layer of Co–N3 sites inhibited the transport of H2O*/OH*, while Co NCs promoted the transport of H2O*/OH* and increased the amount of available H2O* on Co–N3 sites by disordering the rigid interfacial water network. Theoretical calculation showed that the coupling interface structure destroyed the rigid interfacial network, and Co NCs modified the electronic structure of Co–N3 sites, which is beneficial to H2O dissociation and H adsorption, thus accelerating the HER process. This work opens up new avenues for the construction of coupling catalysts from the atomic scale to activate the interfacial water for boosting HER electrocatalysis.

The electrical conductivity of amorphous carbon/reduced graphene oxide(rGO)-wrapped Co3O4 nanofibers prepared by the electrospinning process is for the first time finely tuned creatively by the thermal-etching process in a controlled O2 environment.

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The holiday effect is a useful tool to estimate the impact on air pollution due to changes in human activities. In this study, we assessed the variations in concentrations of fine particulate matter (PM 2.5 ) and nitrogen dioxide (NO 2 ) during the holidays in the heating season from 2014 to 2018 based on daily surface air quality monitoring measurements in Beijing. A Generalized Additive Model (GAM) is used to analyze pollutant concentrations for 34 sites by comprehensively accounting for annual, monthly, and weekly cycles as well as the nonlinear impacts of meteorological factors. A Saturday effect was found in the downtown area, with about 4% decrease in PM 2.5 and 3% decrease in NO 2 relative to weekdays. On Sundays, the PM 2.5 concentrations increased by about 5% whereas there were no clear changes for NO 2 . In contrast to the small effect of the weekend, there was a strong holiday effect throughout the region with average increases of about 22% in PM 2.5 and average reductions of about 11% in NO 2 concentrations. There was a clear geographical pattern in the strength of the holiday effect. In rural areas the increase in PM 2.5 is related to the proportion of coal and biomass consumption for household heating. In the suburban areas between the Fifth Ring Road and Sixth Ring Road there were larger reductions in NO 2 than downtown which might be due to decreased traffic as many people return to their hometown for the holidays. This study provides insights into the pattern of changes in air pollution due to human activities. By quantifying the changes, it also provides insights for improvements in air quality due to control policies implemented in Beijing during the heating season.

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Selecting ultrathin MOF nanosheets as pre-assembling platforms, yolk-shell structured few-layer N-doped carbon (NC) shell encapsulated Ni 0.85 Se core (denoted as Ni 0.85 Se@NC) via an oriented phase modulation (OPM) strategy are controllably fabricated. The ultrathin nature of MOF nanosheets give rise to the modification of structure at the electronic level with abundant Se-vacancies and effective electronic coupling via the Ni-N x coordination at the interface between the Ni 0.85 Se core and NC shell. The obtained Ni 0.85 Se@NC exhibits low overpotentials for both oxygen evolution reaction (OER) (300 mV) and hydrogen evolution reaction (HER) (157 mV) at 10 mA•cm-2 in alkaline condition, outperforming the corresponding bulk MOFderived counterparts. Through exploiting Ni 0.85 Se@NC as anode and cathode catalysts, a low cell voltage of 1.61 V is achieved to perform alkaline water electrolysis. Remarkably, it also achieves high activity in natural seawater (pH = 7.98) and simulated seawater (pH = 7.86) electrolytes, even surpassing integrated Pt/C-RuO 2 /CC electrodes. Density functional theory (DFT) studies illustrate that abundant Se-vacancies effectively regulate the electronic structure of Ni 0.85 Se@NC by accelerating electron transfer from Ni to N atoms at the interface, and thus make the Ni 0.85 Se@NC a near-optimal electronic configuration to stimulate ideal adsorption free energy toward key reaction intermediates.