Comment on mr-2026-7

Abstract

Abstract. Spectroelectrochemical nuclear magnetic resonance (NMR) experiments are faced with numerous challenges originating from shielding effects and susceptibility gradients in samples, leading to inhomogeneous static magnetic fields B0 and radio frequency (rf) fields B1. Moreover, magnetic feedback caused by eddy currents in conductors can obstruct precise measurements. Previous works have shown that these eddy current induced magnetic field distortions can be accurately predicted by finite element method (FEM) simulations. In this work, we present a workflow combining FEM predictions with quantum optimal control (QOC) to tailor custom NMR pulses that exploit specific magnetic field distortions for selective excitation of affected sample regions. The desired selectivity was achieved using pattern pulses optimized for a particular B1 or Larmor frequency ν0. Experimental validation was performed on a heterogeneous phantom consisting of two cavities filled with two spectroscopically distinguishable liquids, one between copper disks to mimic an electrochemical cell, and one between polymer disks as reference. An over 30-fold suppression of the reference resonance in between polymer compared to the resonance in between copper disks was achieved, demonstrating how QOC-tailored pulses can selectively address FEM-predicted B1 distortions to achieve spatial selectivity. It was also demonstrated how QOC-tailored pulses can selectively excite specific ν0 despite of B0 distortions, which implies that difficulties with conventional solvent suppression techniques in electrochemical setups can be mitigated using the adjustable robustness of QOC-tailored pulses. The presented approach sets the stage for gradient-free, localized in operando NMR in electrochemistry and material sciences, with the prospect of surface selectivity down to the detection limit of the setup.

Authors 8

1. Johannes F. Kochs Aachen Institute of Technical and Macromolecular Chemistry

   Forschungszentrum Jülich · RWTH Aachen University

   Affiliation as printed

   Forschungszentrum Jülich GmbH, Institute of Energy Technologies, Fundamental Electrochemistry (IET-1), Jülich, Germany

   Institute of Technical and Macromolecular Chemistry, RWTH Aachen University, Aachen, Germany

2. Armin J. Römer Aachen Institute of Technical and Macromolecular Chemistry

   Forschungszentrum Jülich · RWTH Aachen University

   Affiliation as printed

   Forschungszentrum Jülich GmbH, Institute of Energy Technologies, Fundamental Electrochemistry (IET-1), Jülich, Germany

   Institute of Technical and Macromolecular Chemistry, RWTH Aachen University, Aachen, Germany

3. Michael Schatz

   Forschungszentrum Jülich

   Affiliation as printed

   Forschungszentrum Jülich GmbH, Institute of Energy Technologies, Fundamental Electrochemistry (IET-1), Jülich, Germany

4. M. Streun

   Forschungszentrum Jülich

   Affiliation as printed

   Forschungszentrum Jülich GmbH, Institute of Technology and Engineering (ITE), Jülich, Germany

5. Sven Jovanovic

   Forschungszentrum Jülich

   Affiliation as printed

   Forschungszentrum Jülich GmbH, Institute of Energy Technologies, Fundamental Electrochemistry (IET-1), Jülich, Germany

6. Rüdiger‐A. Eichel Aachen Faculty of Mechanical Engineering Institute of Physical Chemistry

   Forschungszentrum Jülich · RWTH Aachen University

   Affiliation as printed

   Faculty of Mechanical Engineering, RWTH Aachen University, Aachen, Germany

   Forschungszentrum Jülich GmbH, Institute of Energy Technologies, Fundamental Electrochemistry (IET-1), Jülich, Germany

   Institute of Physical Chemistry, RWTH Aachen University, Aachen, Germany

7. S. Kocher

   Forschungszentrum Jülich · Fritz Haber Institute of the Max Planck Society

   Affiliation as printed

   Forschungszentrum Jülich GmbH, Institute of Energy Technologies, Fundamental Electrochemistry (IET-1), Jülich, Germany

   Fritz Haber Institute of the Max Planck Society, Berlin, Germany

8. Josef Granwehr Aachen Institute of Technical and Macromolecular Chemistry

   Forschungszentrum Jülich · RWTH Aachen University

   Affiliation as printed

   Forschungszentrum Jülich GmbH, Institute of Energy Technologies, Fundamental Electrochemistry (IET-1), Jülich, Germany

   Institute of Technical and Macromolecular Chemistry, RWTH Aachen University, Aachen, Germany