The job of a catalyst is to ultimately speed up reactions, which could reduce an hour-long process into several minutes. It has recently been shown that using external magnetic fields to modulate spin states of single-atom catalysts (SACs) is highly effective—enhancing oxygen evolution reaction magnetocurrent by a staggering 2,880%.
With this in mind, researchers at Tohoku University proposed a completely novel strategy to apply an external magnetic field to modulate spin states, and thereby improve electrocatalytic performance.
The study, published in Nano Letters, provides valuable insights regarding the development of efficient and sustainable electrochemical technologies for ammonia production and wastewater treatment.
In the field of electrocatalysis, traditional methods mainly focus on adjusting the chemical composition and structure of catalysts.
The introduction of magnetic-induced spin state modulation provides a new dimension for catalyst design and performance improvement. It involves the regulation of the electronic spin state of the catalyst through an external magnetic field, which can precisely control the adsorption and desorption processes of reaction intermediates, thus effectively reducing the activation energy of the reaction and allowing it to proceed more quickly.
“More efficient production processes can reduce costs, which may translate into lower prices for products such as fertilizers and treated water at the consumer level,” explains Hao Li of Tohoku University’s Advanced Institute for Materials Research (WPI-AIMR).
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(a) Data mining on the magnetic field-enhanced electrocatalysis, including (b) the number of closely related literature and improved performance for ORR, (c) CO2RR and NO2-RR, and (d) the water splitting reactions. All literature data and the corresponding references were extracted via a large-scale data mining from the experimental literature published during the past decade, which are also available in the public Digital Catalysis Platform (DigCat) database. Credit: Nano Letters (2025). DOI: 10.1021/acs.nanolett.5c01516
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(a) Schematic representation of the synthetic process of Ru SAs/N-C and Ru NPs/N-C catalysts. (b) HAADF-STEM image of Ru SAs/N-C. (c) Elemental mapping of Ru SAs/N-C. (d) XRD patterns of Ru NPs/N-C and Ru SAs/N-C. (e) EPR spectra of Ru NPs/N-C and Ru SAs/N-C. (f) The high-resolution Ru 3p spectra of Ru NPs/N-C and Ru SAs/N-C. (g) The high-resolution N 1s spectra of Ru SAs/N-C. (h) Normalized Ru K-edge XANES curves. (i) EXAFS R-space fitting curve. Credit: Nano Letters (2025). DOI: 10.1021/acs.nanolett.5c01516
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(a) Schematic test equipment of nitrate reduction reaction (NitRR) under a constant magnetic field. (b) The LSV curves of Ru NPs/N-C in the 0.1 M K2SO4 with 2.5 mM KNO3, Ru NPs/N-C in the 0.1 M K2SO4 with 2.5 mM KNO3 under magnetic field, Ru SAs/N-C in the 0.1 M K2SO4, Ru SAs/N-C in the 0.1 M K2SO4 under magnetic field and Ru SAs/N-C in the 0.1 M K2SO4 with 2.5 mM KNO3 under magnetic field. (c) NH3 yield rates and (d) FEs of Ru NPs/N-C, and Ru SAs/N-C at various applied potentials with or without magnetic field. (e) Comparison of the NH3 yield rates and FEs of Ru SAs/N-C under magnetic field with other reported electrocatalysts. (f) 1H NMR spectra of the electrolyte fed by K14NO3 and K15NO3 after NitRR. (g) Comparison of the amount of NH3 produced under four different conditions. (h) The long-term stability of Ru SAs/N-C with time-dependent current density curve and yield (inset) for the duration of 10 hours. (i) Cycling tests of Ru SAs/N-C at -0.6 V vs RHE. Credit: Nano Letters (2025). DOI: 10.1021/acs.nanolett.5c01516
The study used advanced characterization techniques to prove that the magnetic field causes the transition to a high spin state, which improves nitrate adsorption.
The theoretical analysis also shows the specific mechanics of why the spin state transition improves the electrocatalytic ability. When exposed to an external magnetic field, the Ru-N-C electrocatalyst demonstrated a high NH3 yield rate (~38 mg L-1 h-1) and a Faradaic efficiency of ~95% for over 200 hours.
This represents a significant improvement compared to the exact same catalyst, but without a boost from an external magnetic field.
Ultimately, this work enriches our theoretical understanding of electrocatalysis by exploring the relationship between magnetic fields, spin states, and catalytic performance.
At the same time, the experimental results offer a reference for future research and the development of new catalysts, laying a solid foundation for the practical application of electrochemical technologies.
The key findings from this study are available on the Digital Catalysis Platform (DigCat), the largest experimental and computational catalysis database to date developed by the Hao Li Lab.
More information:
Xingchao You et al, Magnetic-Field-Induced Spin Transition in Single-Atom Catalysts for Nitrate Electrolysis to Ammonia, Nano Letters (2025). DOI: 10.1021/acs.nanolett.5c01516
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Tohoku University
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Single-atom catalysts change spin state when boosted by a magnetic field (2025, May 30)
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