Non-linear spin correlation of intermediates in enhanced electrochemical nitrate reduction under magnetic fields†

Spin in electrocatalysis introduces a pivotal degree of freedom for overcoming thermodynamic and kinetic limitations. Paradigm studies on spin-related enhancement in oxygen electrocatalysis have highlighted the potential role of spin in influencing reaction kinetics. However, establishing spin correlations in reactions involving complex catalytic conversions, such as NH₃ synthesis, remains a significant challenge. Herein, we reveal spin correlations in electrochemical nitrate reduction (NO₃⁻RR) by demonstrating enhanced activity under external magnetic fields. The yield rate enhancement under magnetic fields is demonstrated on magnetic CuFe₂O₄ at 93.2% for NH₃ production and more than one order of magnitude for NO₂⁻ production. Linear and non-linear correlations between the activity enhancement and spin polarization improvement of CuFe₂O₄ are revealed for NO₃⁻RR toward NO₂⁻ and NH₃, respectively. Insights into spin polarization are provided on intermediates with different net spins, which facilitates the development of magnetic electrocatalysts for NO₃⁻RR.