Nitrogen Doping of Amorphous Carbon Surfaces

Kaukonen, Maria; Nieminen, Risto M.; Pöykkö, S.; Seitsonen, Ari P.

doi:10.1103/physrevlett.83.5346

Cited by 37 publications

(18 citation statements)

References 22 publications

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“…[16] The resulting carbon was amorphous, as revealed by the XRD patterns (Figure 5a), and contained 4.0 at% N, as determined by EA. [16,30,31] The fabricated N-doped carbon was amorphous with a flaky morphology, as shown by the SEM and TEM images (Figure 5d-f). [30] The XPS profile of N revealed the presence of graphitic N (0.92 at%) at 401.4 eV, pyrrolic N (1.84 at%) at 400.1 eV, and pyridinic N (1.44 at%) at 398.4 eV.…”

Section: Effects Of N-doped Carbon Electrocatalyst Layermentioning

confidence: 86%

Metal‐Free Artificial Photosynthesis of Carbon Monoxide Using N‐Doped ZnTe Nanorod Photocathode Decorated with N‐Doped Carbon Electrocatalyst Layer

Jang

Bhatt

Lee

et al. 2018

Advanced Energy Materials

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hindered by serious challenges, including the high overpotential (or low rate) for the reduction of CO 2 and the low selectivity of the reaction forming a broad spectrum of product mixtures. [4] Thus, highly efficient AP for a desired single product is very difficult and requires advanced materials for photoelectrodes and electrocatalysts. Recently, ZnTe has been developed as a promising photocathode material for CO 2 reduction because of its beneficial properties such as a visible-light-active low bandgap (2.3 eV) and a strong driving force for CO 2 reduction with the most negative conduction band edge position (−1.63 V RHE ) among known p-type semiconductors. [5,6] However, ZnTe has drawbacks of low charge separation efficiency both in the bulk and on the surface, photo electrochemical (PEC) instability in aqueous solutions, and poor selectivity for CO 2 -derived products relative to water-derived hydrogen. [5][6][7][8] In the present study, we attempt to fabricate a highly effective ZnTe photocathode having a 1D nanorod structure with substitutional nitrogen doping into the Te sites in order to improve light harvesting and charge transport characteristics. Unlike the conventional N-doping method involving post-treatment using a N 2 , N 2 O, or NH 3 gas, sodium amide (NaNH 2 ) precursor is utilized in the electrode preparation step to achieve nontoxic, one-step N-doping at a low temperature. [9][10][11][12] In addition, a N-doped carbon (N:C) overlayer is employed as the electrocatalyst instead of typical precious metals such as Au, Re, Pt, and Rh. Thus, charge transfer is facilitated because of the unique high conductivity of carbon and CO is selectively produced by stabilization and activation of the surface-bound CO 2 on the N sites with lone-pair electrons. [13][14][15] Here, we strategically fabricate the N-doped carbon electrocatalyst by annealing a polymer obtained from hexamethylenetetramine (HMT) and resorcinol. [16] The combination of the N-doped ZnTe nanorod photocatalyst and the N-doped carbon electrocatalyst layer affords an efficient photocathode for the photoelectrochemical reduction of CO 2 to fuels under sunlight at a low applied bias. At −0.11 V RHE (the theoretical CO 2 /CO redox potential), the integrated photocathode exhibits photocurrents at least fourfold higher than that observed with bare ZnTe nanorods. In addition, the An artificial photosynthesis system based on N-doped ZnTe nanorods decorated with an N-doped carbon electrocatalyst layer is fabricated via an all-solution process for the selective conversion of CO 2 to CO. Substitutional N-doping into the ZnTe lattice decreases the bandgap slightly and improves the charge transfer characteristics, leading to enhanced photoelectrochemical activity. Remarkable N-doping effects are also demonstrated by the N-doped carbon layer that promotes selective CO 2 -to-CO conversion instead of undesired water-to-H 2 reduction by providing active sites for CO 2 adsorption and activation, even in the absence of metallic redox centers. The photocathod...

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Section: Effects Of N-doped Carbon Electrocatalyst Layermentioning

confidence: 86%

Metal‐Free Artificial Photosynthesis of Carbon Monoxide Using N‐Doped ZnTe Nanorod Photocathode Decorated with N‐Doped Carbon Electrocatalyst Layer

Jang

Bhatt

Lee

et al. 2018

Advanced Energy Materials

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“…Kaukonen et al19 suggested based on their density functional theoretical (DFT) calculation that a single N atom substitution at a sp 3 or sp 2 site in an a‐C subsurface layers increases the total density of states (TDOS) below the energy gap resulting in Fermi energy ( E f ) level moving down and the work function increasing. Whereas substitution on the sp 1 and sp 2 rings in the outer surface leads to TDOS increase near the conduction band edge with the Fermi level moving up and the work function decreasing.…”

Section: Discussionmentioning

confidence: 99%

“…Based on this interpretation it seems that N substitution in this study is dominant at the sp 1 , sp 2 rings in the outer surface for ''SN'' type N-doped films, that is, the ''SN'' atomic species substitute preferentially at the sp 1 and sp 2 rings compared to the ionic N species. Nitrogen doping of a-C is known to increase the sp 2 /sp 3 ratio and density functional theoretical (DFT) calculations 19 suggests that N atoms positioned at an sp 3 site decreases their coordination number with resulting sp 2 N (or N with a non-planar threefold coordination). It therefore seems logical that N atoms positioned at an sp 1 or sp 2 sites could increase the co-ordination number with resulting sp 2 N or sp 3 N respectively.…”

Section: Discussionmentioning

confidence: 99%

The human micro‐vascular endothelial cells in vitro interaction with atomic‐nitrogen‐doped diamond‐like carbon thin films

et al. 2007

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This paper reports the initial response of atomic nitrogen doped diamond like carbon (DLC) to endothelial cells in vitro. The introduction of nitrogen atoms/molecules to the diamond like carbon structures leads to an atomic structural change favorable to the attachment of human micro-vascular endothelial cells. Whilst the semi-conductivity induced by nitrogen in DLC is thought to play a part, the increase in the non-bonded N atoms and N(2) molecules in the atomic doped species (with the exclusion of the charged species) seems to contribute to the improved attachment of human microvascular endothelial cells. The increased endothelial attachment is associated with a lower work function and slightly higher water contact angle in the atomic doped films, where the heavy charged particles are excluded. The films used in the study were synthesized by the RF PECVD technique followed by post deposition doping with nitrogen, and afterwards the films were characterized by XPS, Raman spectroscopy, SIMS and Kelvin probe. The water contact angles were measured, and the counts of the adherent endothelial cells on the samples were carried out. This study is relevant and contributory to improving biocompatibility of surgical implants and prostheses.

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“…Capacitance Kelvin and the I-V probes suggest that in the N-doped DLC (without the use of sweep plate) the CPD and the density of state (DOS) decreased, indicating a Fermi level rise. 11 However, Kaukonen et al 13 suggested based on their density function theoretical (DFT) calculation that a single N atom substitution at an sp 3 or sp 2 site in an a-C subsurface layers increases the total density of states (TDOS) below the energy gap, resulting in Fermi energy (E f ) level moving down and the increase in work function. However, substitution on the sp 1 and sp 2 rings in the outer surface leads to TDOS increase near the conduction band edge with the Fermi level moving up and the work function decreasing.…”

Section: Endothelial Cellular Interactionmentioning

confidence: 98%

“…3 ratio and density function theoretical (DFT) calculations 13 suggests that N atoms positioned at a sp 3 site decreases their coordination number with resulting sp 2 N (or N with a nonplanar threefold coordination). Nitrogen incorporation into DLC normally reduces the contact angle (increases the surface energy), 1 though it seems that N-neutral specie ("SN") doping increased the contact angle in this study (Figure 1).…”

Section: /Spmentioning

confidence: 99%

Human microvascular endothelial cellular interaction with atomic N‐doped DLC compared with Si‐doped DLC thin films

et al. 2006

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This article reports results of endothelial cell interaction with atom beam source N-doped a-C:H (diamond-like carbon, DLC) as it compares with that of Si-doped DLC thin films. The RF plasma source exhibits up to 40% N-dissociation and N-atomic fluxes of approximately 0.85 x 10(18) atoms/s, which ensures better atomic nitrogen incorporation. Two different types of nitrogen species (with and without the use of sweep plates to remove charged ions) were employed for nitrogen doping. The number of attached endothelial cells is highest on Si-DLC, followed by the N-DLC (where the sweep plates were used to remove ions), the N-DLC (without the use of sweep plates), undoped DLC, and finally the uncoated sample. The contact angle values for these films suggest that water contact angle is higher in the atomic nitrogen neutral films and Si-DLC films compared to the ionized-nitrogen specie doped films and undoped DLC thin films, suggesting that the more hydrophobic films, semiconducting films, and film with relieved stress have better interaction with human microvascular endothelial cells. It seems evident that N-doping increases the Raman I(D)/I(G) ratios, whereas N-neutral doping decreases it slightly and Si-doping decreases it even further. In this study, lower Raman I(D)/I(G) ratios are associated with increased sp(3)/sp(2) ratio, an increased H concentration, photoluminescence intensity, and a higher endothelial cellular adhesion. These investigations could be relevant to biocompatibility assessment of nanostructured biomaterials and tissue engineering.

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Nitrogen Doping of Amorphous Carbon Surfaces

Cited by 37 publications

References 22 publications

Metal‐Free Artificial Photosynthesis of Carbon Monoxide Using N‐Doped ZnTe Nanorod Photocathode Decorated with N‐Doped Carbon Electrocatalyst Layer

Metal‐Free Artificial Photosynthesis of Carbon Monoxide Using N‐Doped ZnTe Nanorod Photocathode Decorated with N‐Doped Carbon Electrocatalyst Layer

The human micro‐vascular endothelial cells in vitro interaction with atomic‐nitrogen‐doped diamond‐like carbon thin films

Human microvascular endothelial cellular interaction with atomic N‐doped DLC compared with Si‐doped DLC thin films

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