Immobilizing a Lehn-Type Catalyst with Nitrocyclocondensation Chemistries: CO₂ Reduction on Silicon Hybrid Photoelectrodes
We present the first examples of installing a redox reporter and CO₂ reduction (CO₂R) catalyst onto freshly HF-etched Si (photo)electrodes using a solution-phase nitrocyclocondensation (NCC) reaction. Previous studies detailed the mechanism of NCC reactions on Si under ultrahigh vacuum conditions but have not applied these chemistries to generate functional (photo)electrodes. Installing 4-nitrophenyl ferrocene (4-NpFc) molecules directly onto degenerately doped p⁺Si allowed us to evaluate the effects of different NCC reaction conditions on coverage (e.g., 3.6 ± 1.2 × 10⁻¹¹ mol/cm²) and electrochemical reversibility. The 4-NpFc molecules remained immobilized under the reducing potentials (−2.0 V vs Fc⁺ᐟ⁰ in acetonitrile) needed to drive molecular CO₂R catalysts. Installing 4-nitroaniline (4-NA) molecules onto low-doped pSi allowed us to couple Lehn-type Re(I) catalysts with pendant carboxylic acids. The CO Faradaic efficiency of CO production under 1-sun illumination (−2.15 V vs Fc⁺ᐟ⁰) was 23% in CO₂-saturated electrolyte, a value that surpasses previous examples of CO2R catalyst monolayers on Si. These two examples highlight the versatility of solution-phase NCC attachment chemistries for generating functional Si (photo)electrodes.
Orr, A. D.; Zhu, Z.; Durand, N.; Bonfiglio, A.; Teitsworth, T. S.; Sampaio, R. N.; Castellano, F. N.; Cahoon, J. F.; Donley, C. L.; Lockett, M. R. Immobilizing a Lehn-Type Catalyst with Nitrocyclocondensation Chemistries: CO₂ Reduction on Silicon Hybrid Photoelectrodes, ACS Appl. Mater. Interfaces, 2025, In press. https://doi.org/10.1021/acsami.5c03638
