DOE OSTI · 2889127
Electron Inversion and Tunneling at Silicon Thermal Oxide Interfaces for Solar-Driven Molecular Catalysis to Syngas
Abstract
Semiconductor photoelectrodes are regularly coupled to solid-state heterogeneous catalysts to perform solar-driven reduction of CO 2 . Less frequently, molecular catalysts are employed to better control the reactivity toward desired products, yet the development of robust semiconductor/molecule interfaces has proven challenging. Here, we demonstrate that a 2–3 nm thermal oxide layer on Si exhibits stability in aqueous solution, high photovoltage, and a photocurrent density of ∼10 mA/cm 2 for the solar-driven photoelectrochemical reduction of a homogeneous molecular catalyst, producing syngas with an ∼2:1 H 2 to CO ratio. Because of a low defect density, the oxide interface forms an electron inversion layer with metal-like electron density at cathodic potentials. This inversion layer facilitates electron transfer to redox-active molecules via tunneling even if the molecule’s reduction potential is beyond the semiconductor’s conduction band edge. Using an electrolyte solution composed of a homogeneous cobalt bis(terpyridine) catalyst in a water/organic solvent mixture, stable photoelectrochemistry was observed under 1-sun illumination, exhibiting an ∼30% Faradaic efficiency for CO that was similar to a glassy carbon electrode under comparable conditions. Furthermore, the results demonstrate that an ultrathin thermal oxide interface is a robust platform for development of aqueous-stable, molecule-driven photoelectrocatalysis.
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He, Shi [University of North Carolina at Chapel Hill, NC (United States)], Bottum, Samuel R. [University of North Carolina at Chapel Hill, NC (United States)] (ORCID:0000000281806692), Dickenson, John C. [University of North Carolina at Chapel Hill, NC (United States)] (ORCID:0000000277886810), Margavio, Hannah R. M. [North Carolina State University, Raleigh, NC (United States)] (ORCID:0000000153273713), Keller, Niklas D. [University of North Carolina at Chapel Hill, NC (United States)] (ORCID:000000031581072X), Oyetade, Oluwaseun A. [University of North Carolina at Chapel Hill, NC (United States)] (ORCID:0000000303344573), Gentile, Ryan J. [University of North Carolina at Chapel Hill, NC (United States)], Teitsworth, Taylor S. [University of North Carolina at Chapel Hill, NC (United States)] (ORCID:0000000184879785), Shin, Samuel J. [University of North Carolina at Chapel Hill, NC (United States)], Dempsey, Jillian L. [University of North Carolina at Chapel Hill, NC (United States)] (ORCID:0000000294594166), Miller, Alexander J. M. [University of North Carolina at Chapel Hill, NC (United States)] (ORCID:0000000193903951), Sampaio, Renato N. [University of North Carolina at Chapel Hill, NC (United States)] (ORCID:0000000271586470), Tereniak, Stephen J. [University of North Carolina at Chapel Hill, NC (United States)] (ORCID:0000000349780020), Donley, Carrie L. [University of North Carolina at Chapel Hill, NC (United States)] (ORCID:000000030906306X), Lockett, Matthew R. [University of North Carolina at Chapel Hill, NC (United States)] (ORCID:0000000348517757), Parsons, Gregory N. [North Carolina State University, Raleigh, NC (United States)] (ORCID:0000000200485859), Meyer, Gerald J. [University of North Carolina at Chapel Hill, NC (United States)] (ORCID:0000000242276393), Cahoon, James F. [University of North Carolina at Chapel Hill, NC (United States)] (ORCID:000000031780215X). 2025-03-18. Electron Inversion and Tunneling at Silicon Thermal Oxide Interfaces for Solar-Driven Molecular Catalysis to Syngas. https://doi.org/10.1021/jacs.4c17251
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