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Oyetade OA, Wang Y, He S, Margavio HRM, Bottum SR, Rooney CL, Wang H, Donley CL, Parsons GN, Cohen-Karni T, Cahoon JF. Covalent Functionalization of Silicon with Plasma-Grown "Fuzzy" Graphene: Robust Aqueous Photoelectrodes for CO 2 Reduction by Molecular Catalysts. ACS APPLIED MATERIALS & INTERFACES 2024; 16:37885-37895. [PMID: 38996184 DOI: 10.1021/acsami.4c04691] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 07/14/2024]
Abstract
Carbon electrodes are ideal for electrochemistry with molecular catalysts, exhibiting facile charge transfer and good stability. Yet for solar-driven catalysis with semiconductor light absorbers, stable semiconductor/carbon interfaces can be difficult to achieve, and carbon's high optical extinction means it can only be used in ultrathin layers. Here, we demonstrate a plasma-enhanced chemical vapor deposition process that achieves well-controlled deposition of out-of-plane "fuzzy" graphene (FG) on thermally oxidized Si substrates. The resulting Si|FG interfaces possess a silicon oxycarbide (SiOC) interfacial layer, implying covalent bonding between Si and the FG film that is consistent with the mechanical robustness observed from the films. The FG layer is uniform and tunable in thickness and optical transparency by deposition time. Using p-type Si|FG substrates, noncovalent immobilization of cobalt phthalocyanine (CoPc) molecular catalysts was employed for the photoelectrochemical reduction of CO2 in aqueous solution. The Si|FG|CoPc photocathodes exhibited good catalytic activity, yielding a current density of ∼1 mA/cm2, Faradaic efficiency for CO of ∼70% (balance H2), and stable photocurrent for at least 30 h at -1.5 V vs Ag/AgCl under 1-sun illumination. The results suggest that plasma-deposited FG is a robust carbon electrode for molecular catalysts and suitable for further development of aqueous-stable Si photocathodes for CO2 reduction.
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Affiliation(s)
- Oluwaseun A Oyetade
- Department of Chemistry, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599-3290, United States
| | - Yingqiao Wang
- Department of Materials Science and Engineering, Carnegie Mellon University, Pittsburgh, Pennsylvania 15213, United States
| | - Shi He
- Department of Chemistry, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599-3290, United States
| | - Hannah R M Margavio
- Department of Chemical and Biomolecular Engineering, North Carolina State University, Raleigh, North Carolina 27695, United States
| | - Samuel R Bottum
- Department of Chemistry, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599-3290, United States
| | - Conor L Rooney
- Department of Chemistry, Yale University, New Haven, Connecticut 06520, United States
- Energy Sciences Institute, Yale University, West Haven, Connecticut 06516, United States
| | - Hailiang Wang
- Department of Chemistry, Yale University, New Haven, Connecticut 06520, United States
- Energy Sciences Institute, Yale University, West Haven, Connecticut 06516, United States
| | - Carrie L Donley
- Chapel Hill Analytical and Nanofabrication Laboratory (CHANL), University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599, United States
| | - Gregory N Parsons
- Department of Chemical and Biomolecular Engineering, North Carolina State University, Raleigh, North Carolina 27695, United States
| | - Tzahi Cohen-Karni
- Department of Materials Science and Engineering, Carnegie Mellon University, Pittsburgh, Pennsylvania 15213, United States
| | - James F Cahoon
- Department of Chemistry, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599-3290, United States
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Welch BC, Antonio EN, Chaney TP, McIntee OM, Strzalka J, Bright VM, Greenberg AR, Segal-Peretz T, Toney M, George SM. Building Semipermeable Films One Monomer at a Time: Structural Advantages via Molecular Layer Deposition vs Interfacial Polymerization. CHEMISTRY OF MATERIALS : A PUBLICATION OF THE AMERICAN CHEMICAL SOCIETY 2024; 36:1362-1374. [PMID: 38370278 PMCID: PMC10870709 DOI: 10.1021/acs.chemmater.3c02519] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 10/03/2023] [Revised: 12/29/2023] [Accepted: 01/02/2024] [Indexed: 02/20/2024]
Abstract
Molecular layer deposition (MLD) provides the opportunity to perform condensation polymerization one vaporized monomer at a time for the creation of precise, selective nanofilms for desalination membranes. Here, we compare the structure, chemistry, and morphology of two types of commercial interfacial polymerzation (IP) membranes with lab-made MLD films. M-phenylenediamine (MPD) and trimesoyl chloride (TMC) produced a cross-linked, aromatic polyamide often used in reverse osmosis membranes at MLD growth rates of 2.9 Å/cycle at 115 °C. Likewise, piperazine (PIP) and TMC formed polypiperazine amide, a common selective layer in nanofiltration membranes, with MLD growth rates of 1.5 Å/cycle at 115 °C. Ellipsometry and X-ray reflectivity results suggest that the surface of the MLD films is comprised of polymer segments roughly two monomers in length, which are connected at one end to the cross-linked bulk layer. As a result of this structure as well as the triple-functionality of TMC, MPD-TMC had a temperature window of stable growth rate from 115 to 150 °C, which is unlike any non-cross-linked MLD chemistries reported in the literature. Compared to IP films, corresponding MLD films were denser and morphologically conformal, which suggests a reduction in void volumes; this explains the high degree of salt rejection and reduced flux previously observed for exceptionally thin MPD-TMC MLD membranes. Using X-ray photoelectron spectroscopy and infrared spectroscopy, MLD PIP-TMC films evidenced a completely cross-linked internal structure, which lacked amine and carboxyl groups, pointing to a hydrophobic bulk structure, ideal for optimized water flux. Grazing-incidence wide-angle X-ray scattering showed broad features in each polyamide with d-spacings of 5.0 Å in PIP-TMC compared to that of 3.8 Å in MPD-TMC. While MLD and IP films were structurally identical to PIP-TMC, MPD-TMC IP films had a structure that may have been altered by post-treatment compared to MLD films. These results provide foundational insights into the MLD process, structure-performance relationships, and membrane fabrication.
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Affiliation(s)
- Brian C. Welch
- Israel
Institute of Technology, Haifa 3200003, Israel
- University
of Colorado Boulder, Boulder, Colorado 80309, United States
| | - Emma N. Antonio
- University
of Colorado Boulder, Boulder, Colorado 80309, United States
| | - Thomas P. Chaney
- University
of Colorado Boulder, Boulder, Colorado 80309, United States
| | - Olivia M. McIntee
- University
of Colorado Boulder, Boulder, Colorado 80309, United States
| | - Joseph Strzalka
- Argonne
National Laboratory, Lemont, Illinois 60439, United States
| | - Victor M. Bright
- University
of Colorado Boulder, Boulder, Colorado 80309, United States
| | - Alan R. Greenberg
- University
of Colorado Boulder, Boulder, Colorado 80309, United States
| | | | - Michael Toney
- University
of Colorado Boulder, Boulder, Colorado 80309, United States
| | - Steven M. George
- University
of Colorado Boulder, Boulder, Colorado 80309, United States
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