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Highly efficient photocatalytic H₂ evolution from water using visible light and structure-controlled graphitic carbon nitride.

Martin DJ, Qiu K, Shevlin SA, Handoko AD, Chen X, Guo Z, Tang J - Angew. Chem. Int. Ed. Engl. (2014)

Bottom Line: Herein, an effective strategy for synthesizing extremely active graphitic carbon nitride (g-C3N4) from a low-cost precursor, urea, is reported.The reaction proceeds for more than 30 h without activity loss and results in an internal quantum yield of 26.5% under visible light, which is nearly an order of magnitude higher than that observed for any other existing g-C3N4 photocatalysts.Furthermore, it was found by experimental analysis and DFT calculations that as the degree of polymerization increases and the proton concentration decreases, the hydrogen-evolution rate is significantly enhanced.

View Article: PubMed Central - PubMed

Affiliation: Solar Energy Group, Department of Chemical Engineering, UCL, Torrington Place, London, WC1E 7JE (UK).

No MeSH data available.


Ratios of bonds within the N 1s core-level peak in different samples and their comparisonto the hydrogen-evolution rate (HER) under visible light(λ>395 nm): Decreasing proton concentration leads to adramatic increase in photocatalytic activity.
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fig02: Ratios of bonds within the N 1s core-level peak in different samples and their comparisonto the hydrogen-evolution rate (HER) under visible light(λ>395 nm): Decreasing proton concentration leads to adramatic increase in photocatalytic activity.

Mentions: Figure 2 shows the distinctive trend in bondingratios versus activity between samples (see also Table S1). The ratio of sp2C—N—C bonds to the sum of sp3H—N—[C]3 and C—NHx bonds(the latter represents the total amount of protons) is 2.83 in urea, 2.7 for thiourea, and only 2.31in DCDA. As it is part of the heptazine ring, linked by a double and a single bond to two opposingcarbon atoms, the sp2-bonded nitrogen atom is the principle participant that contributesto band-gap absorption and therefore is an extremely important part of the structure. Bothhybridized sp3 nitrogen atoms and surface functional amino groups(C—NHx) are also key features when considering bulk and surfaceproperties. Along with C—NHx bonding, graphitic carbon nitridepossesses a positively charged, acidic surface, as confirmed by ζ-potential measurements (seeFigure S8). Elemental analysis (EA) further confirmed the trend shown in Figure 2: As bulk H (atom %) increases, the HER per SSA(μmol m−2 h−1) decreases (seeFigure S9). From these results and in combination with XPS analysis, we could conclude that alower proton concentration leads to a larger HER.


Highly efficient photocatalytic H₂ evolution from water using visible light and structure-controlled graphitic carbon nitride.

Martin DJ, Qiu K, Shevlin SA, Handoko AD, Chen X, Guo Z, Tang J - Angew. Chem. Int. Ed. Engl. (2014)

Ratios of bonds within the N 1s core-level peak in different samples and their comparisonto the hydrogen-evolution rate (HER) under visible light(λ>395 nm): Decreasing proton concentration leads to adramatic increase in photocatalytic activity.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4257501&req=5

fig02: Ratios of bonds within the N 1s core-level peak in different samples and their comparisonto the hydrogen-evolution rate (HER) under visible light(λ>395 nm): Decreasing proton concentration leads to adramatic increase in photocatalytic activity.
Mentions: Figure 2 shows the distinctive trend in bondingratios versus activity between samples (see also Table S1). The ratio of sp2C—N—C bonds to the sum of sp3H—N—[C]3 and C—NHx bonds(the latter represents the total amount of protons) is 2.83 in urea, 2.7 for thiourea, and only 2.31in DCDA. As it is part of the heptazine ring, linked by a double and a single bond to two opposingcarbon atoms, the sp2-bonded nitrogen atom is the principle participant that contributesto band-gap absorption and therefore is an extremely important part of the structure. Bothhybridized sp3 nitrogen atoms and surface functional amino groups(C—NHx) are also key features when considering bulk and surfaceproperties. Along with C—NHx bonding, graphitic carbon nitridepossesses a positively charged, acidic surface, as confirmed by ζ-potential measurements (seeFigure S8). Elemental analysis (EA) further confirmed the trend shown in Figure 2: As bulk H (atom %) increases, the HER per SSA(μmol m−2 h−1) decreases (seeFigure S9). From these results and in combination with XPS analysis, we could conclude that alower proton concentration leads to a larger HER.

Bottom Line: Herein, an effective strategy for synthesizing extremely active graphitic carbon nitride (g-C3N4) from a low-cost precursor, urea, is reported.The reaction proceeds for more than 30 h without activity loss and results in an internal quantum yield of 26.5% under visible light, which is nearly an order of magnitude higher than that observed for any other existing g-C3N4 photocatalysts.Furthermore, it was found by experimental analysis and DFT calculations that as the degree of polymerization increases and the proton concentration decreases, the hydrogen-evolution rate is significantly enhanced.

View Article: PubMed Central - PubMed

Affiliation: Solar Energy Group, Department of Chemical Engineering, UCL, Torrington Place, London, WC1E 7JE (UK).

No MeSH data available.