Doubling of photocatalytic H2 evolution from g-C3N4 via its nanocomposite formation with multiwall carbon nanotubes: Electronic and morphological effects

Suryawanshi, Anil; Dhanasekaran, P.; Mhamane, Dattakumar; Kelkar, Sarika; Patil, S. F.; Gupta, Nandini; Ogale, Satishchandra

doi:10.1016/j.ijhydene.2012.03.123

Cited by 127 publications

(68 citation statements)

References 25 publications

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“…Adsorption on mac-SiO2 therefore modifies condensation and aggregation presumably by restricting the mobility of condensing CN oligomers. The role, if any, of the carbonaceous component in controlling photocatalysis is hard to deconvolute, but is clearly not responsible for increasing excited state lifetimes, as previously noted for other carbon nitride/carbon composites, [17,60,[89][90][91][92] and hence rate enhancements are unlikely to originate through improved charge separation. A direct catalytic role for the carbonaceous material cannot be discounted, however the limited impact on charge separation suggests that this component is not directly responsible for the increased photoactivity of composites versus bulk CN.…”

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confidence: 94%

Pore confinement effects and stabilization of carbon nitride oligomers in macroporous silica for photocatalytic hydrogen production

Qiao

Mitchell

Coulson

et al. 2016

Carbon

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An ordered macroporous host (mac-SiO2) has been used to prevent aggregation of layered photocatalysts based on carbon nitride. Using typical carbon nitride synthesis conditions, cyanamide was condensed at 550 o C in the presence and absence of mac-SiO2. Condensation in the absence of mac-SiO2 results in materials with structural characteristics consistent with the carbon nitride, melon, accompanied by ca. 2 wt% carbonization. For mac-SiO2 supported materials, condensation occurs with greater carbonization (ca. 6 wt%). On addition of 3wt% Pt cocatalyst photocatalytic hydrogen production under visible light is found to be up to 10 times greater for the supported composites. Time-resolved photoluminescence spectroscopy shows that excited state relaxation is more rapid for the mac-SiO2 supported materials suggesting faster electron-hole recombination and that supported carbon nitride does not exhibit improved charge separation. CO2 temperature programmed desorption indicates that enhanced photoactivity of supported carbon nitride is attributable to an increased surface area compared to bulk carbon nitride and an increase in the concentration of weakly basic catalytic sites, consistent with carbon nitride oligomers.

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mentioning

confidence: 94%

Pore confinement effects and stabilization of carbon nitride oligomers in macroporous silica for photocatalytic hydrogen production

Qiao

Mitchell

Coulson

et al. 2016

Carbon

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“…Photoluminescence (PL) has been used to monitor PL quenching, which has been attributed to either transfer of photoexcited charges or energy transfer between semiconductor and nanocarbon . For example, Kamat and co‐workers have added increasing concentrations of both carbon nanotubes (CNTs) and graphene to ZnO nanoparticle solution and observed a decrease in PL signal, from which they deduced the presence of electron transfer from ZnO to the nanocarbon.…”

Section: Characteristics Of the Light Sources Used To Perform Detpmmentioning

confidence: 99%

Dual Excitation Transient Photocurrent Measurement for Charge Transfer Studies in Nanocarbon Hybrids and Composites

Cherevan

Eder

2016

Adv Materials Inter

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the nanocarbon itself. In fact, it is known that the electrical properties of CNTs [ 23,24 ] and graphene [ 25 ] are strongly infl uenced by light, hence this inherent behavior of the nanocarbons needs to be considered for TPM on nanocarbon-based hybrids and composites.The photoresponse of CNTs has generated considerable debate during the last few decades and only recently its bolometric nature has been experimentally confi rmed. [ 26 ] The theory implies that light illumination of CNTs creates excitons with unusually high binding energies, [ 27 ] which cannot directly contribute to the photoconductivity. In this scenario, they have to dissociate thermally, therefore locally heating up the nanocarbon matrix. The increase in temperature leads to an increase in conductivity of the CNTs (in contrast to 3D metals, as explained by the Luttinger liquid model for 1D conductors. [ 28,29 ] ) and results in additional photocurrent.This knowledge, however, has not yet been implemented into practice and standard photocurrent measurements on nanocarbon hybrids and composites are still conducted without considering the photoresponse of bare CNTs. Here we report a new technique, which we describe as dual excitation transient photocurrent measurement (DETPM). This technique allows for distinguishing the bolometric effect (i.e., intrinsic conductivity change due to heat produced by light irradiation) from a potential photoexcited charge transfer in CNTs-based hybrids. We have tested this technique on two high-performance hybrids, CNT-TiO 2 and CNT-Ta 2 O 5 , and explicitly demonstrate the presence of the charge transfer from the semiconductor to the nanocarbon in both the cases.We synthesized the CNT-Ta 2 O 5 hybrid via a modifi ed sol-gel process and the CNT-TiO 2 hybrid via atomic layer deposition process (details of synthesis are in the Experimental Section and characterization in ESI). We aimed to create hybrids with a high degree of conformal coating and an extended interface between the CNTs and the metal oxide to maximize the interfacial charge transfer. SEM images of both hybrids in Figure S1 (Supporting Information) confi rm the presence of uniform coating on the nanocarbon surface and demonstrate homogeneity of the samples. As further revealed by high-resolution transmission electron microscopy (HRTEM) in Figure 1 b,c a tight interface between the two components was established in both the cases. Importantly, all samples used for the TPM were prepared in the form of free-standing macroscopic membranes to eliminate any substrate contribution. In a typical DETPM experiment, a macroscopic membrane, containing either pure CNTs (i.e., reference) or the CNT-based hybrids, was connected to two electrodes as shown in Figure 2 a and a small bias was applied to establish a constant current.

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“…[17][18][19] However,t heir widespread applications are largely limitedb yt heir high cost and scarcity.I nr ecent years, transition metals (e.g.,N i),t ransition metal sulfides/hydroxides (e.g., NiS, CoS, MoS 2 ,N iS 2 ,N i(OH) 2 ), and nanocarbons (e.g.,g raphene,c arbon nanotube) have been reporteda se ffective noble-metal-free co-catalysts for g-C 3 N 4 in the photocatalytic H 2 evolution reaction. [20][21][22][23][24][25][26][27][28] Nevertheless, despite all these inspiringr esults, the development of earth-abundant elementbased co-catalysts with improved efficiencya nd high stability remains al ong-standing scientific challenge in the photocatalytic H 2 evolution process.…”

Section: Introductionmentioning

confidence: 99%

Graphitic C₃N₄ Decorated with CoP Co‐catalyst: Enhanced and Stable Photocatalytic H₂ Evolution Activity from Water under Visible‐light Irradiation

Zhao

Jiang

Cai

2017

Chemistry An Asian Journal

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In this work, graphitic C N decorated with a CoP co-catalyst (g-C N /CoP) is reported for photocatalytic H evolution reaction based on two-step hydrothermal and phosphidation method. The structure of g-C N /CoP is well confirmed by XRD, FTIR, TEM, XPS, and UV/Vis diffuse reflection spectra techniques. When the weight percentage of CoP loading is 3.4 wt % (g-C N /CoP-3.4 %), the highest H evolution amount of 8.4×10 μmol g is obtained, which is 1.1×10 times than that over pure g-C N . This value also is comparable with that of g-C N loaded by the same amount of Pt. In cycling experiments, g-C N /CoP-3.4 % shows a stable photocatalytic activity. In addition, g-C N /CoP-3.4 % is an efficient photocatalyst for H evolution under irradiation with natural solar light. Based on comparative photoluminescence emission spectra, photoelectrochemical I-t curves, EIS Nyquist plots, and polarization curves between g-C N /CoP-3.4 % and pure g-C N , it is concluded that the presence of the CoP co-catalyst accelerates the separation and transfer of photogenerated electrons of g-C N , thus resulting in improved photocatalytic activity in the H evolution reaction.

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Doubling of photocatalytic H2 evolution from g-C3N4 via its nanocomposite formation with multiwall carbon nanotubes: Electronic and morphological effects

Cited by 127 publications

References 25 publications

Pore confinement effects and stabilization of carbon nitride oligomers in macroporous silica for photocatalytic hydrogen production

Pore confinement effects and stabilization of carbon nitride oligomers in macroporous silica for photocatalytic hydrogen production

Dual Excitation Transient Photocurrent Measurement for Charge Transfer Studies in Nanocarbon Hybrids and Composites

Graphitic C₃N₄ Decorated with CoP Co‐catalyst: Enhanced and Stable Photocatalytic H₂ Evolution Activity from Water under Visible‐light Irradiation

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Doubling of photocatalytic H2 evolution from g-C3N4 via its nanocomposite formation with multiwall carbon nanotubes: Electronic and morphological effects

Cited by 127 publications

References 25 publications

Pore confinement effects and stabilization of carbon nitride oligomers in macroporous silica for photocatalytic hydrogen production

Pore confinement effects and stabilization of carbon nitride oligomers in macroporous silica for photocatalytic hydrogen production

Dual Excitation Transient Photocurrent Measurement for Charge Transfer Studies in Nanocarbon Hybrids and Composites

Graphitic C3N4 Decorated with CoP Co‐catalyst: Enhanced and Stable Photocatalytic H2 Evolution Activity from Water under Visible‐light Irradiation

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Graphitic C₃N₄ Decorated with CoP Co‐catalyst: Enhanced and Stable Photocatalytic H₂ Evolution Activity from Water under Visible‐light Irradiation