Search

3d transition metal catalysts are effective for the electrocatalytic nitrogen (N2) reduction reaction (NRR) to produce ammonia (NH3), but the role of active sites remains elusive. Herein, a series of iron–cobalt oxyhydroxide hollow nanocages (FeCoOOH HNCs) were constructed via controlled Co doping. The as-obtained FeCoOOH HNCs with an Fe/Co ratio of 1 : 1 exhibited a high faradaic efficiency of 14.7% and superior NH3 formation rate of 16.8 µg h−1 mgcat−1 at −0.3 V vs. RHE. In situ Raman spectra disclose the existence of intermediates and identify the reaction pathway. Density functional theory (DFT) calculations reveal that Co doping could lower the energy barrier of *N2 → *NNH → *NNHH, induced by the preferential proton adsorption on Co sites to drive NH3 electrosynthesis. Moreover, FeCoOOH HNCs with a suitable Fe/Co ratio could boost the *N2 activation due to the bolstered polarization of adsorbed N2, while increasing the energy barrier for the hydrogen evolution reaction. This work provides an intriguing strategy towards efficient NRR electrocatalysis by the elaborate design of two 3d transition metals. [ABSTRACT FROM AUTHOR]

Earth-abundant elements are highly desirable electrocatalysts for artificial N2 fixation (NRR). However, most earth-abundant elements are inactive for the NRR, and the competitive hydrogen evolution reaction (HER) causes inferior faradaic efficiency. Thus, facile modification methods to transform an NRR-unfavorable electrocatalyst into its NRR-favorable counterpart are highly demanded. Herein, we present an efficient hydrophobic carbon layer incorporation strategy on tin monosulfide (SnS@C) to greatly boost the NRR activity of SnS. The hydrophobic carbon layer can limit proton availability at the electrode surface while integrating the advantages of strong N2 adsorption and better conductivity that synergistically improve the NRR performance. Specifically, SnS@C delivers a high faradaic efficiency of 14.56% and NH3 yield of 7.95 × 10−11 mol s−1 cm−2 (24.33 μgNH3 h−1 mgcat−1) at −0.5 V versus the reversible hydrogen electrode. It also exhibits durable stability for consecutive electrolysis over 18 h. Adequate control and 15N isotopic labeling experiments confirm the reliability of N sources. Density functional theory calculations reveal that the superior activity is attributed to the redistribution and bias of electrons between the SnS and carbon-layer interface. This work highlights that the simple hydrophobic carbon layer incorporation strategy could guide the design and modification of advanced NRR catalysts. [ABSTRACT FROM AUTHOR]