Tunable Syngas Formation at Industrially Relevant Current Densities via CO2 Electroreduction and Hydrogen Evolution over Ni and Fe-derived Catalysts obtained via One-Step Pyrolysis of Polybenzoxazine Based Composites.

Simultaneous electroreduction of CO2 and H2O to syngas can provide a sustainable feed for established processes used to synthesize carbon-based chemicals. The synthesis of MOx/M-N-Cs (M = Ni, Fe) electrocatalysts reported via one-step pyrolysis that shows increased performance during syngas electrosynthesis at high current densities with adaptable H2/CO ratios, e.g., for the Fischer-Tropsch process. When embedded in gas diffusion electrodes (GDEs) with optimized hydrophobicity, the NiOx/Ni-N-C catalyst produces syngas (H2/CO = 0.67) at -200 mA cm-2 while for the FeOx/Fe-N-C syngas production occurs at ≈-150 mA cm-2. By tuning the electrocatalyst's microenvironment, stable operation for >3 h at -200 mA cm-2 is achieved with the NiOx/Ni-N-C GDE. Post-electrolysis characterization revealed that the restructuring of the catalyst via reduction of NiOx to metallic Ni NPs still enables stable operation of the electrode at -200 mA cm-2, when embedded in an optimized microenvironment. The ionomer and additives used in the catalyst layer are important for the observed stable operation. Operando Raman measurements confirm the presence of NiOx during CO formation and indicate weak adsorption of CO on the catalyst surface.