Key Takeaways & Executive Findings
- •• (FeCoNiMoCr)Sx high-entropy sulfide achieves an NH3 yield rate of 47.97 μg/(h·mgcat) at −0.7 V vs RHE and a Faradaic efficiency of 26.1% at −0.4 V vs RHE, outperforming other metal compositions. • The two-step solvothermal synthesis enables the formation of high-entropy sulfides with multiple metal components, which exhibit enhanced charge transport and abundant active sites for NRR. • The synergistic effects among Fe, Co, Ni, Mo, and Cr in the high-entropy structure suppress the competing hydrogen evolution reaction, improving NRR selectivity. • This work provides a rational design strategy for high-entropy sulfide electrocatalysts, offering a promising pathway for sustainable ammonia synthesis under ambient conditions.
Abstract
Eco-friendly electrocatalytic nitrogen reduction reaction (NRR) is aimed to replace the traditional polluting industrial process, but NRR needs electrocatalysts with high selectivity and activity to boost desired NH3 yield rate and Faradic efficiency (FE). In this work, high-entropy sulfides (HES) (FeCoNiMoM)Sx (M=Cr, Cu, Mn) were synthesized via a two-step solvothermal method. The optimized composition for HES is (FeCoNiMoCr)Sx, with promising NRR performance that NH3 yield rate reached 47.97 μg/(h·mgcat) at −0.7 V vs RHE and FE was 26.1% at −0.4 V vs RHE. Comprehensive characterization and electrochemical testing were performed to investigate the effects of the metal component on NRR performance. It reveals that (FeCoNiMoCr)Sx shows more intense charge transport, more electrocatalytic active sites, higher selectivity, etc, resulting from the electron transport and element synergy of HES. Also, it is proved to have targeted NRR selectivity and limiting competitive hydrogen evolution reaction. The results offer promising guidance for further improving the NRR electrocatalysts based on transition elements.
1. Introduction
NH3 is a vital strategic resource in chemical, agricultural, power and other fields and it has been produced in Haber-Bosch process since the 20th century [1]. This traditional Haber-Bosch process reaction pathway is: N2(g)+3H2(g)→2NH3(g), which requires high temperature and high pressure due to the high energy and unpolarized bond of N2, thus polluting the environment and occupying over 1% of the global power consumption [2]. Therefore, it is worth focusing on an environmentally friendly ammonia synthesis process with high efficiency [3].
Electrocatalytic nitrogen reduction reaction (NRR) is regarded as an efficient method to promote gas reaction and has many advantages such as carrying out under room pressure and temperature (NPT), easy to be controlled and clean product. So electrocatalysis shows the probability of reducing N2 to NH3 just in the solution under NPT [4]. NRR provides ideas and methods to mitigate the greenhouse effect and energy crisis. However, electrocatalysts are required to have high activity and selectivity to reduce N2 to ammonia because of the high barrier of the reaction [5]. During the NRR, the violent competing reaction, hydrogen evolution reaction (HER), is also going on the surface of the catalyst, leading to a limited NH3 yield rate and low Faradic efficiency (FE), especially compared to other reported clean and efficient electrocatalytic ammonia production [6 −9]. Also, the limited N2 solubility in water leads to undesirable NH3 production [10]. So, the primary task for the design of NRR electrocatalysts is to decrease HER selectivity and increase NH3 yield rate.
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WANG Jia-yi, LIU Xin-li, WU Zhuang-zhi, WANG De-zhi (2025). High-entropy metal sulfide nanoparticles with optimized metal composition as highly efficient electrocatalysts for N2 reduction to NH3. Journal of Central South University. https://doi.org/10.1007/s11771-025-6101-5
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Frequently Asked Questions
What is the main finding of this study?
The study demonstrates that high-entropy sulfide (FeCoNiMoCr)Sx exhibits excellent electrocatalytic performance for nitrogen reduction to ammonia, achieving an NH3 yield rate of 47.97 μg/(h·mgcat) and a Faradaic efficiency of 26.1%.
How were the high-entropy sulfides synthesized?
The high-entropy sulfides were synthesized via a two-step solvothermal method, which allowed the incorporation of multiple metal elements (Fe, Co, Ni, Mo, and Cr) into a single sulfide phase.
Why is the high-entropy composition beneficial for NRR?
The high-entropy composition enhances charge transport, provides more active sites, and promotes synergistic effects among metal elements, which together improve NRR selectivity and suppress the competing hydrogen evolution reaction.
What are the implications of this research?
This research offers a promising strategy for designing efficient and cost-effective electrocatalysts for sustainable ammonia synthesis, potentially replacing the energy-intensive Haber-Bosch process.
What is the significance of the Faradaic efficiency achieved?
A Faradaic efficiency of 26.1% is relatively high for NRR catalysts, indicating that a significant portion of the electrical energy is used for ammonia production rather than hydrogen evolution, which is crucial for practical applications.
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