Use email button above to contact.

Detailed molecular level understanding of organometallic electrocatalytic systems is required to fully exploit their technological potential to store, distribute, and utilise renewable energy in chemical form. However, in situ methods providing high resolution information on the structure and reactivity of transient intermediates remain challenging due to incompatible requirements for standard electrochemical and spectroscopic cell designs. Here, we demonstrate the use of spectroelectrochemical nuclear magnetic resonance (SEC-NMR) to enable operando characterisation of molecular species during organometallic electrocatalysis. The electroreduction of a prototypical molecular rhodium(+I) diphosphine complex was studied under aprotic conditions and in the presence of H ₂O and/or CO ₂. By combining multinuclear SEC-NMR, chemical reductions, modelling and simulations, we determine the involved species, their relative concentrations and the competing interconversions. The bielectronic reduction leading to the highly reactive low-valent rhodium(−I) intermediate and subsequent protonation of that species into a Rh–hydride complex was followed in a time-resolved manner. Deuterium labelling and ex situ NMR analysis after SEC-NMR electrolysis revealed that under aprotic conditions the proton source substantially arises from Hofmann elimination of the nBu ₄NPF ₆ electrolyte in addition to the acetonitrile solvent. The reactivities of the Rh(−I) and the Rh–H complexes were further monitored under turnover conditions, providing direct molecular insights into bifurcating electrocatalytic pathways for hydrogen evolution and CO ₂ reduction.

• UV-Vis_data contains ASCII files that represent data displayed in figure 2. The first row in all ASCII files states the point in time in seconds of the respective measurement. The following columns alternatingly state wavelength in nm and absorbance in arbitrary units (a.u.) of the respective measurements.
  • CA_at_-2V_blank.dat includes several measurements used as blank.
  • CA_at_-2V_0s+1s+5s+30s.dat represents measurements during chronoamperometry at -2V after 0s, 1s, 5s and 30s.
  • CA_at_-2V_0s+1s+5s+30s_calc_blank.dat represents measurements during chronoamperometry at -2V after 0s, 1s, 5s and 30s considering the blank measurement.
• NMR_data contains NMR raw data from TopSpin. Subfolders are named according the scheme: X_Y_Z
  X: Experiment with or without Rh complex: either 'Rh' or 'noRh'.
  Y: Gaseous environment/electrolyte saturation of experiment: either 'Ar' or '13CO2'.
  Z: Type of solvent: either 'CD3CN+THF-d8', 'THF-d8', 'THF' or 'CH3CN'. '+H2O' or '+D2O' indicates the addition of 20µL H2O or D2O, respectively.
  These folders contain subfolders each representing a single measurement. These subfolders are consecutively numbered representing the chronological order of measurements.
  • Rh_Ar_CD3CN+THF-d8: ³¹P spectra displayed in Figure 2 (top left) and evaluated in S5, S6 and S12 are stored in folders '1' to '13' in subfolder '31P'; ¹H spectra displayed in Figure S7 are stored in folders '1' to '13' in subfolder '1H'; the ex situ ¹H spectrum displayed in figure S8 and S10 is stored in folder 'ex_situ' in subfolder '1H'; ²H spectra displayed in figure S9 are stored in folders '1' and '2' in subfolder '2H'; the ex situ ³¹P spectrum displayed in figure S11 is stored in folder 'ex_situ' in subfolder '31P'.
  • Rh_Ar_THF-d8+H2O: ³¹P spectra displayed in Figure 2 (bottom left) and evaluated in S13 and S16 are stored in folders '1' to '12' in subfolder '31P'; ¹H spectra displayed in Figure S14 are stored in folders '1' to '13' in subfolder '1H'; the ex situ ¹H spectrum displayed in figure S15 is stored in folder 'ex_situ' in subfolder '1H'.
  • Rh_13CO2_CH3CN: ³¹P spectra displayed in Figure 2 (top right) and evaluated in S17 (left) and S18 (left) are stored in folders '1' to '5' in subfolder '31P'; ¹³C spectra displayed in Figure S20 are stored in folders '1' to '6' in subfolder '13C'.
  • Rh_13CO2_THF-d8+H2O: ³¹P spectra displayed in Figure 2 (bottom right) and evaluated in S17 (right) and S18 (right) are stored in folders '1' to '13' in subfolder '31P'; ¹³C spectra displayed in Figure S21 are stored in folders '1' to '6' in subfolder '13C'; ¹H spectra are stored in folders '1' to '13' in subfolder '1H'; the ex situ ¹H spectrum displayed in Figure S19 is stored in folder 'ex_situ' in subfolder '1H'; the ex situ ³¹P spectrum is stored in folder 'ex_situ' in subfolder '31P'; the ex situ ¹³C spectrum is stored in folder 'ex_situ' in subfolder '13C'.
  • noRh_Ar_THF+H2O: ³¹P spectra displayed in Figure S22 and evaluated in Figure S23 are stored in folders '1' to '13' in subfolder '31P'; ¹H spectra are stored in folders '1' to '13' in subfolder '1H'; the ex situ ¹H spectrum displayed in Figure S24 is stored in folder 'ex_situ' in subfolder '1H'; the ex situ ³¹P spectrum is stored in folder 'ex_situ' in subfolder '31P'.
• Electrochemical_data contains raw data from EC-Lab acquired during spectroelectrochemical NMR experiments. The respective subfolders are named according the same scheme as the respective NMR data folder (see above). All .mps files describe the parameters and order of electrochemical experiments, which are stored as binary EC-Lab .mpr files. For all experiments, the order of measurements was: EIS, OCV, CP and a second OCV.
  • Rh_Ar_CD3CN+THF-d8: 221121_a_inOp_RhCell_GC-WE_Ptmesh-CE_Pt-RE_Rh_THF-d8+CD3CN_Ar.mps
  • Rh_Ar_THF-d8+H2O: 221115_d_inOp_RhCell_GC-WE_Ptmesh-CE_Pt-RE_Rh_THF-d8+H2O.mps
  • Rh_13CO2_CH3CN: 221010_b_inOp_RhCell_GC-WE_Ptmesh-CE_Pt-RE_Rh_CH3CN+13CO2.mps
  • Rh_13CO2_THF-d8+H2O: 250326_b_inOp_RhCell_GC-WE_Ptmesh-CE_Pt-RE_Rh_THF-d8+13CO2+H2O.mps
  • noRh_Ar_THF+H2O: 221130_b_inOp_RhCell_GC-WE_Ptmesh-CE_Pt-RE_Rh_THF+H2O.mps
• Electrolysis_data contains chronoamperometry (CA) electrolysis data and gas chromatography (GC) data acquired during CO₂ and CO₂/H₂O electrolysis experiments. The folder is divided into subfolders according to the electrolyte composition. The .txt files are stored in the German (de-DE) format, with commas as decimal digit separator.
  • Electrolysis-CO2 contains data from CO₂ electrolysis experiments. Electrolysis A and B are two repeated experiments under equal conditions.
    • Electrolysis A:
      • A_CA-Electrolysis-CO2.txt contains chronoamperometry data of the electrolysis experiment. Columns are: time in seconds, working electrode potential (Ewe) in V, current in mA, and charge in C.
      • GC-Calibration subfolder contains calibration measurements with defined gas mixtures (20%, 40%, 60%, 80%, 100%) used for quantification of GC analysis.
      • GC-Electrolysis subfolder contains GC measurements during electrolysis at different time points (0.5 h, 1 h, 1.5 h, 2 h, 2.5 h, 3 h) and a blank measurement (0 h). Each file lists peak tables and compound results including retention time, peak area, height, concentration, and identification of gas species (e.g., H₂, O₂, N₂, CO, CO₂).
    • Electrolysis B:
      • B_CA-Electrolysis-CO2.txt contains chronoamperometry data of the electrolysis experiment.
      • GC-Calibration subfolder contains calibration measurements with defined gas mixtures (38%, 50%, 65%, 86%, 100%).
      • GC-Electrolysis subfolder contains GC measurements during electrolysis at different time points (0.5 h to 4 h in 0.5 h intervals) and a blank measurement (0 h).
  • Electrolysis-CO2-H2O contains data from CO₂ electrolysis experiments with addition of H₂O.
    • C_CA-Electrolysis-CO2-H2O.txt contains chronoamperometry data of the electrolysis experiment.
    • GC-Calibration subfolder contains calibration measurements with defined gas mixtures (20%, 40%, 60%, 80%, 100%).
    • GC-Electrolysis subfolder contains GC measurements during electrolysis at different time points (0.5 h, 1 h, 1.5 h, 2 h, 2.5 h, 3 h, 3.5 h, 4 h) and a blank measurement (0 h).
• DFT-files contains data from density functional theory (DFT) calculations performed with Gaussian16. The data are organized in three subfolders:
  • out-files-DFT contains Gaussian output files (*.out) for all calculated species. These files include input specifications (basis sets, functional, charge, multiplicity), SCF convergence, optimized geometries, and calculated electronic energies. Example species include CO, CO₂, H₂O, HCO₂^–, H₃O⁺, and various Rh complexes in different oxidation states and with different ligands (e.g., Rh(0)-CO, Rh(I)-CO₂H, Rh(-I)).
  • xyz-files-optimized contains Cartesian coordinates of the optimized geometries (*.xyz) for the same set of molecules and complexes. Each line lists the atom type followed by its x, y, z coordinates in Å. Example (opt_CO.xyz):

    C    0.000000000   0.000000000  -0.640356000
    O    0.000000000   0.000000000   0.480267000
            

  • xyz-files-start contains the starting geometries (*.xyz) used as input for the DFT optimizations, with the same file structure as the optimized xyz files.