Structure–Activity Relationships in Bulk Polymeric and Sol–Gel-Derived Carbon Nitrides during Photocatalytic Hydrogen Production

Hollmann, Dirk; Karnahl, Michael; Tschierlei, Stefanie; Kailasam, Kamalakannan; Schneider, Mat­thias; Radnik, Jörg; Grabow, Kathleen; Bentrup, Ursula; Junge, Henrik; Beller, Matthias; Lochbrunner, Stefan; Thomas, Arne; Brückner, Angelika

doi:10.1021/cm500034p

Cited by 112 publications

(100 citation statements)

References 47 publications

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“…In comparison to the as-prepared samples without Pt, the deposition of Pt NPs leads to a drop of the CB-e − EPR signal, indicating that those electrons are transferred to Pt from which they react with protons to produce H 2 [20]. Interestingly, the EPR intensity under UV-vis irradiation ( Figure 6) seems to reflect somehow the catalytic behavior (compare Figure 1a).…”

Section: Charge Separation and Transfermentioning

confidence: 92%

“…The catalytic test results suggest that (i) the Pt cocatalyst is needed for effective H 2 formation over CN-based photocatalysts since it promotes electron transfer from the conduction band of CN to Pt and, thus, suppresses fast electron-hole recombination [20]; (ii) Composite formation of AIS with CN is detrimental for H 2 formation rates, yet it improves stability (iii) Despite the fact that AIS is able to absorb visible light (evidenced by UV-vis diffuse reflectance spectra, Figure S1) electron-hole separation and/or electron transfer might be inefficient and prevent proton reduction. (iv) The pH of the reaction solution has a significant impact on the stability of the Pt/CN catalyst.…”

Section: Catalytic Activitymentioning

confidence: 99%

“…In situ-EPR is a versatile technique to monitor separation and transfer of photogenerated electrons in semiconductors based on oxides [30] or carbon nitrides [20], since electrons excited to the conduction band (CB-e − ) can be trapped at oxygen vacancies [30] and carbon defects [24]. All as-prepared CN-containing catalysts show a narrow isotropic singlet with Lorentzian line shape at g = 2.0042 already in the dark (not shown) arising from single electrons trapped at a surface sp 2 -carbon in a typical heptazine unit [31,32].…”

Section: Charge Separation and Transfermentioning

confidence: 99%

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Relations between Structure, Activity and Stability in C3N4 Based Photocatalysts Used for Solar Hydrogen Production

et al. 2018

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Solar hydrogen production from water could be a sustainable and environmentally friendly alternative to fossil energy carriers, yet so far photocatalysts active and stable enough for large-scale applications are not available, calling for advanced research efforts. In this work, H 2 evolution rates of up to 1968 and 5188 µmol h −1 g −1 were obtained from aqueous solutions of triethanolamine (TEOA) and oxalic acid (OA), respectively, by irradiating composites of AgIn 5 S 8 (AIS), mesoporous C 3 N 4 (CN, surface area >150 m 2 /g) and ≤2 wt.% in-situ photodeposited Pt nanoparticles (NPs) with UV-vis (≥300 nm) and pure visible light (≥420 nm). Structural properties and electron transport in these materials were analyzed by XRD, STEM-HAADF, XPS, UV-vis-DRS, ATR-IR, photoluminescence and in situ-EPR spectroscopy. Initial H 2 formation rates were highest for Pt/CN, yet with TEOA this catalyst deactivated by inclusion of Pt NPs in the matrix of CN (most pronounced at λ ≥ 300 nm) while it remained active with OA, since in this case Pt NPs were enriched on the outermost surface of CN. In Pt/AIS-CN catalysts, Pt NPs were preferentially deposited on the surface of the AIS phase which prevents them from inclusion in the CN phase but reduces simultaneously the initial H 2 evolution rate. This suggests that AIS hinders transport of separated electrons from the CN conduction band to Pt NPs but retains the latter accessible by protons to produce H 2 .

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Section: Charge Separation and Transfermentioning

confidence: 92%

Section: Catalytic Activitymentioning

confidence: 99%

Section: Charge Separation and Transfermentioning

confidence: 99%

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Relations between Structure, Activity and Stability in C3N4 Based Photocatalysts Used for Solar Hydrogen Production

et al. 2018

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“…7 Interestingly, the organic carbon nitride photocatalyst has been effective for hydrogen evolution under visible light irradiation 8 whereas, a Pt-containing graphitic carbon nitride (g-CN) system has been investigated to uncover the charge separation and recombination phenomena. 9 Several efficient systems with a combination of activity. In addition, Ag or Au nanoparticles deposited on g-CN nanocomposites were also studied to achieve plasmonic enhancement in the photocatalytic activity.…”

mentioning

confidence: 99%

Nickel as a co-catalyst for photocatalytic hydrogen evolution on graphitic-carbon nitride (sg-CN): what is the nature of the active species?

et al. 2016

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The nature of a nickel-based co-catalyst deposited on a sol-gel prepared porous graphitic-carbon nitride (sg-CN), for photocatalytic H 2 production from water, has been investigated. The formation of the active catalytic species, charge separation and recombination of the photogenerated electrons and holes during photochemical H 2 evolution has been determined for the first time using in situ EPR spectroscopy.

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“…Synthesis temperature affects the extent of the 2D ordering within the polymer and hence the number of defects present in the structure, which may be paramagnetic [10]. Studying the concentration of the paramagnetic charge carriers as a function of annealing temperature and the influence of band gap irradiation on these may bring new insight into the photocatalytic properties of g-C3N4.…”

Section: Introductionmentioning

confidence: 99%

Impact of the annealing temperature on Pt/g-C 3 N 4 structure, activity and selectivity between photodegradation and water splitting

et al. 2017

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This work presents a systematic study of the effect of fabrication temperature (450 to 650 o C) on the structure and electronic properties of g-C3N4 prepared from melamine. The work is conducted by X-ray diffraction, elemental analysis, BET nitrogen adsorption, UV-vis absorption, and electron paramagnetic resonance (EPR). The photocatalytic activity is tested for hydrogen production in the presence of oxalic acid (OA) as well as triethanolamine (TEOA). A considerable change in the morphology is observed with increasing the synthesis temperature resulting in an increase of the surface area, likely due to thermal etching at elevated temperatures. The decrease of charge carriers' concentration, per unit area, with annealing temperatures may be due to the decrease of the conjugation of the polymer. Probing the activity of g-C3N4 for hydrogen evolution reinforced this conclusion, the rate of hydrogen evolution per unit area for OA as well as TEOA decreased with annealing temperatures. An interesting finding is the correlation between CO2:H2 ratio and the increase in the band gap of g-C3N4 prepared at different temperatures when using oxalic acid as an electron donor. This suggests that water oxidation becomes easier with increasing band gap energy, probably due to a lowering of the valence band edge.

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Structure–Activity Relationships in Bulk Polymeric and Sol–Gel-Derived Carbon Nitrides during Photocatalytic Hydrogen Production

Cited by 112 publications

References 47 publications

Relations between Structure, Activity and Stability in C3N4 Based Photocatalysts Used for Solar Hydrogen Production

Relations between Structure, Activity and Stability in C3N4 Based Photocatalysts Used for Solar Hydrogen Production

Nickel as a co-catalyst for photocatalytic hydrogen evolution on graphitic-carbon nitride (sg-CN): what is the nature of the active species?

Impact of the annealing temperature on Pt/g-C 3 N 4 structure, activity and selectivity between photodegradation and water splitting

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