As an environmentally friendly and sustainable method for ammonia synthesis, nitrogen reduction reaction (NRR) by electrocatalysis possesses several advantages, including viability under mild conditions, abundant reaction raw materials and low energy consumption, and thus it is supposed to be a promising alternative to the traditional Haber–Bosch process. However, the stable NN bonds in the nitrogen (N2) and the competing hydrogen evolution reaction (HER) put harsh requirements on catalysts. In this study, the CoS/MoS2 heterojunction catalyst where CoS nanoparticles are anchored on the MoS2 nanosheets is reported as a high-efficiency NRR catalyst. The catalysts have high NH3 yield (23.23 μg h−1 mgcat.−1), reasonable faradaic efficiency (FE, 12.63%) and long-term electrochemical stability under −0.45 V vs. RHE in 0.1 M Na2SO4 solution, whose performance is better than MoS2 and CoS. The TPV results show rapid interfacial electron transfer and good conductivity of the material, and the DFT calculation reveals that the CoS attached to the (100) plane effectively enhances N2 adsorption and catalysis performance.
Daming Feng,Lixue Zhou,Chang Liu,Hui Li,Yusheng Zhang,Yali Yao,Tianyi Ma
Electrocatalytic nitrogen reduction reaction (NRR) for the synthesis of ammonia (NH 3 ) is one of the green and mild methods of artificial nitrogen fixation, promising as an alternative to replace the existing industrial process. Under the requirements of green chemistry and sustainable development, the design and development of highly active and stable electrocatalysts is very important for improved synthesis performance. Mimicking from the natural nitrogenase, Fe and Mo based catalysts have attracted much attention due to their superior catalytic performance for N 2 adsorption and activation. In this work, an interfacial engineering strategy has been used to prepare a Fe, Mo-bimetallic electrocatalyst for the electrosynthesis of NH 3 . In detail, the pre-pyrolyzed biochar-based Fe 2 O 3 composites were decorated with nano-flowered MoS 2 /MoO 2 hybrids by a solvothermal process (MoS 2 /MoO 2 @Fe 2 O 3 /BC). As confirmed by the extensive characterization, the further modification not only introduced functional counterparts into the electrocatalysts but also regulated the morphology of the nanostructure. The electrochemical tests showed that the highest NH 3 yield rate of MoS 2 /MoO 2 @Fe 2 O 3 /BC was 4.87 μg h − 1 cm −2 and highest FE was 16.5% in 0.1 M Na 2 SO 4 . The catalytic stability and durability were also presented in the longtime electrolysis and cycling experiments. The improved catalytic performance of decorated catalyst, as evidenced by the comparison with Fe 2 O 3 /BC, is attributed to the increased electrocatalytic active area, the moderated hydrophilicity, and the synergistic effect of Fe, Mo-bimetallic active sites. This study provides a new perspective for the design and development of low-cost transition metal complexes as electrocatalysts for nitrogen reduction reactions.
The synthesis of a novel In 2 O 3 /In 2 S 3 microsphere heterostructures is conducted through a well-designed two-step hydrothermal method. These composites are first applied for efficient fixation of N 2 to NH 3 under mild conditions without any organic scavengers and precious-metal cocatalysts. Here the In 2 S 3 flakes are in situ generated and uniformly assembled on In 2 O 3 microsphere. The phase structures, morphologies and oxygen vacancies of the samples are systematically characterized by X-ray powder diffraction (XRD), field-emission scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), UV–vis diffuse-reflectance spectroscopy (DRS), and photoluminescence spectroscopy (PL), Raman, electron spin resonance (ESR) spectroscopy and photoelectrochemistry. Meanwhile, the investigation of photocatalytic performance can confirm that the nitrogen fixation rate of In 2 O 3 /In 2 S 3 (III) heterostructure is 40.04 μmol g −1 h −1 , which is about 4.7 and 6.0 times higher than that of pure In 2 O 3 and In 2 S 3 , respectively.
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