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Competition from hydrogen/oxygen evolution reactions and low solubility of N2 in aqueous systems limited the selectivity and activity on nitrogen fixation reaction. Herein, we design an aerobic‐hydrophobic Janus structure by introducing fluorinated modification on porous carbon nanofibers embedded with partially carbonized iron heterojunctions (Fe3C/Fe@PCNF‐F). The simulations prove that the Janus structure can keep the internal Fe3C/Fe@PCNF‐F away from water infiltration and endow a N2 molecular‐concentrating effect, suppressing the competing reactions and overcoming the mass‐transfer limitations to build a robust "quasi‐solid–gas" state micro‐domain around the catalyst surface. In this proof‐of‐concept system, the Fe3C/Fe@PCNF‐F exhibits excellent electrocatalytic performance for nitrogen fixation (NH3 yield rate up to 29.2 μg h−1 mg−1cat. and Faraday efficiency (FE) up to 27.8 % in nitrogen reduction reaction; NO3− yield rate up to 15.7 μg h−1 mg−1cat. and FE up to 3.4 % in nitrogen oxidation reaction). [ABSTRACT FROM AUTHOR]

The electrochemical N2 reduction reaction (eNRR) is considered to be an attractive alternative to overcome the short‐comings of the Haber‐Bosch method, where the electrocatalysts play a vital role in the eNRR efficiency. Herein, isolated single‐B sites with electron deficiency in intermetallic carbide are rationally designed to trigger charge density redistribution, achieving excellent selectivity for eNRR. The B‐rich VC nanocrystals are in situ synthesized on carbon nanofibers (B‐VC/CNFs), and the ordered intermetallic structure of VC can isolate contiguous B atoms into single‐B sites with specific electronic structures. In light of density functional theory calculations, the as‐designed BCV configuration can regulate the adsorption behavior of N2 and decrease the energy barrier for the proton–electron coupling and transferring process (*NN → *NNH), endowing the distinguished activity and selectivity, as evidenced by excellent Faradaic efficiency of 46.1% and NH3 yield of 0.443 µmol h–1 cm–2. The operando Raman spectra reveals the formation of NH intermediates on the surfaces of B‐VC/CNFs, further confirming the calculated eNRR pathway. This intermetallic carbide host strategy for generating electron‐deficient single‐B sites offers powerful guidelines for designing advanced eNRR electrocatalysts to achieve effective ammonia production. [ABSTRACT FROM AUTHOR]

Vacancy engineering has been proved repeatedly as an adoptable strategy to boost electrocatalysis, while its poor selectivity restricts the usage in nitrogen reduction reaction (NRR) as overwhelming competition from hydrogen evolution reaction (HER). Revealed by density functional theory calculations, the selenium vacancy in ReSe2 crystal can enhance its electroactivity for both NRR and HER by shifting the d‐band from −4.42 to −4.19 eV. To restrict the HER, we report a novel method by burying selenium vacancy‐rich ReSe2@carbonized bacterial cellulose (Vr‐ReSe2@CBC) nanofibers between two CBC layers, leading to boosted Faradaic efficiency of 42.5 % and ammonia yield of 28.3 μg h−1 cm−2 at a potential of −0.25 V on an abrupt interface. As demonstrated by the nitrogen bubble adhesive force, superhydrophilic measurements, and COMSOL Multiphysics simulations, the hydrophobic and porous CBC layers can keep the internal Vr‐ReSe2@CBC nanofibers away from water coverage, leaving more unoccupied active sites for the N2 reduction (especially for the potential determining step of proton‐electron coupling and transferring processes as *NN → *NNH). [ABSTRACT FROM AUTHOR]

• Low-crystallinity WS 2 in carbon nanofiber (WS 2 -CNF) composites are prepared through in-situ confinement effect. • The WS 2 -CNF composite presents fast electrochemical reaction kinetics and excellent structural stability. • The WS 2 -CNF electrode exhibits an ultralong cycling life in sodium-ion batteries. [Display omitted] As a typical metal sulfide, tungsten disulfide (WS 2) with high theoretical capacity has attracted significant attention as the anode for sodium-ion batteries (SIBs). However, WS 2 bulk material usually displays poor rate performance and fast capacity fading in practical applications due to its low conductivity and structural instability. Herein, we propose an in-situ confinement strategy for synthesizing low-crystallinity and ultrafine WS 2 nanosheets within carbon nanofibers (WS 2 -CNF) by the simple heat treatment of electrospun polyacrylonitrile/ammonium tetrathiotungstate (PAN/(NH 4) 2 WS 4) nanofibers. The low-crystallinity structure of WS 2 with ultrasmall size and rich defects can greatly reduce the volume change and shorten the ion diffusion length. WS 2 nanosheets are confined in the CNF matrix, which is capable of effectively improving its electronic conductivity and structural stability. Based on these advantages, the WS 2 -CNF composite electrode demonstrates fast and ultrastable Na+ storage performance with a high capacity of 182 mAh g–1 after 6000 cycles at 5.0 A g−1. Therefore, this work provides a simple and facile strategy for developing high-performance WS 2 anodes for SIBs. [ABSTRACT FROM AUTHOR]

We proposed a conceptual and experimental breakthrough in overcoming the high energy barriers for N 2 absorption and activation by tuning the center positions of pz orbital of boron in S and B co-doped carbon nanofibers (S-B/CNFs). [Display omitted] • CNFs were used as nanoreactor to synthesize B, S co-doped carbon materials. • Results investigated the influences of B, S, P as electron donor on tuning their NRR activity. • S 6.23 -B 8.09 /CNFs exhibits excellent NRR activity with FE of 22.4 % and NH 3 yield of 0.223 μmol h−1 cm-2 at −0.7 V. • S, B doping facilitates the adsorption of N 2 and reduces the energy barriers for rate-determining steps. Herein, we proposed a conceptual and experimental breakthrough in overcoming the high energy barriers for N 2 absorption and activation by tuning the center positions of p z orbital of boron in S and B co-doped carbon nanofibers (S-B/CNFs). We theoretically and experimentally investigated the influences of nonmetallic elements of B as electron acceptor, and S and P as electron donor on tuning NRR activity. We revealed that the heteroatom-doping of S atoms induced changing of center position of the p z orbital of B facilitates the adsorption of N 2 on S-C-B sites and reduces the energy barriers for rate-determining steps. The S 6.23 -B 8.09 /CNFs exhibits the highest NRR activity with high Faradaic efficiency of 22.4 % and NH 3 yield of 0.223 μmol h−1 cm-2 at −0.7 V versus reversible hydrogen electrode. The combined computational and experimental works uncover the relationship between the p -band center of heteroatom doped carbon catalysts and NRR activity. [ABSTRACT FROM AUTHOR]