اشترك بالحزمة الذهبية واحصل على وصول غير محدود شمرا أكاديميا
تسجيل مستخدم جديدPreparation and Characterization of Metal-free graphitic Carbon Nitride Film Photocathodes for Light-induced Hydrogen Evolution
101
0
0.0
(
0
)
اسأل ChatGPT حول البحث
ﻻ يوجد ملخص باللغة العربية
Very recently, it has been shown that an abundant material, polymeric carbon nitride, can produce hydrogen from water under visible-light irradiation in the presence of a sacrificial donor [1]. We will present here the preparation and characterization of graphitic carbon nitride (g-C3N4) films on semiconducting substrates by thermal condensation of dicyandiamide precursor under inert gas conditions. Structural and surface morphological studies of the carbon nitride films suggest a high porosity of g-C3N4 thin film consisting of a network of nanocrystallites. Photo-electrochemical investigations show upon cathodic polarization light-induced hydrogen evolution for a wide range of proton concentrations in the aqueous electrolyte. Additionally, Synchrotron radiation based photoelectron spectroscopy has been applied to study the surface/near-surface chemical composition of the utilized g-C3N4 film photocathodes. For the first time it is shown that g-C3N4 films can be successfully applied as photoelectrochemical material for light induced hydrogen evolution. [1]X. Wang, K. Maeda, A. Thomas, K. Takanabe, G. Xin, J. M. Carlsson, K. Domen, M. Antonietti, Nature Mat. 2009, 8, 76-80.
قيم البحث
اقرأ أيضاً
In this work, we demonstrate that a well-established and facile ball milling approach using mixtures of commercial anatase nanoparticles and TiH2 introduces noble-metal-free photocatalytic H2 activity to titania. We characterize this synergistic effe
ct in view of the nature of defects, state of hydroxylation, and investigate the effect on the energetics and kinetics of electronic states and the resulting H2 evolution performance.
Black TiO2 has gained increasing interest because of its outstanding properties and promising applications in a wide range of fields. Among the outstanding features of the material is that certain synthesis processes lead to the formation of an intri
nsic co-catalytic center and thus enable noble-metal free photocatalytic H2 generation. In this work, we report grey TiO2 by an appropriate hydrogenation treatment exhibits excellent photocatalytic hydrogen. In this case, by the employment of thermally stable and high-surface-area TiO2 nanoparticles as well as mesoporous particles as the hydrogenation precursor, the appropriate extent of reduction of TiO2 (coloration) and the formation of Ti3+ is the key for the efficient noble-metal-free photocatalytic H2 generation. The EPR results reveal that grey TiO2 shows stronger Ti3+ feature at g ca. 1.93 than black TiO2 contributing to the intrinsic catalytic center for H2 evolution.
Electrocatalytic hydrogen evolution reaction (HER) in alkaline media is a promising electrochemical energy conversion strategy. Ruthenium (Ru) is an efficient catalyst with a desirable cost for HER, however, the sluggish H2O dissociation process, due
to the low H2O adsorption on its surface, currently hampers the performances of this catalyst in alkaline HER. Herein, we demonstrate that the H2O adsorption improves significantly by the construction of Ru-O-Mo sites. We prepared Ru/MoO2 catalysts with Ru-O-Mo sites through a facile thermal treatment process and assessed the creation of Ru-O-Mo interfaces by transmission electron microscope (TEM) and extended X-ray absorption fine structure (EXAFS). By using Fourier-transform infrared spectroscopy (FTIR) and H2O adsorption tests, we proved Ru-O-Mo sites have tenfold stronger H2O adsorption ability than that of Ru catalyst. The catalysts with Ru-O-Mo sites exhibited a state-of-the-art overpotential of 16 mV at 10 mA cm-2 in 1 M KOH electrolyte, demonstrating a threefold reduction than the previous bests of Ru (59 mV) and commercial Pt (31 mV) catalysts. We proved the stability of these performances over 40 hours without decline. These results could open a new path for designing efficient and stable catalysts.
Based on first principles calculations, this study reveals that magnetism in otherwise non-magnetic materials can originate from the partial occupation of antibonding states. Since the antibonding wavefunctions are spatially antisymmetric, the spin w
avefunctions should be symmteric according to the exchange antisymmetric principle of quantum mechanics. We demonstrate that this phenomenon can be observed in a graphitic carbon nitride material, $g$-C$_4$N$_3$, which can be experimentally synthesized and seen as a honeycomb structure with a vacancy. Three dangling bonds of N atoms pointing to the vacancy site interact with each other to form one bonding and two antibonding states. As the two antibonding states are near the Fermi level, and electrons should partially occupy the antibonding states in spin polarization, this leads to 1~$mu_B$ magnetic moment.
The design of efficient electrocatalysts for electrochemical water splitting with minimal amount of precious metal is crucial to attain renewable and sustainable energy conversion. Here, we report the use of a network of CdSe branched colloidal nanoc
rystals, made of a CdSe core and eight CdSe pods (so-called octapods), able to host on their pods Pt particles, and thus catalyzing water splitting reactions. Thanks to the octapod shape, the resulting Pt-hosting network is mechanically trapped onto carbon nanotube buckypaper, providing mechanically flexible and binder-free electrodes. We found that such hierarchical configuration maximizes the mass activity and the utilization efficiency of Pt for the hydrogen evolution reaction (HER). At a potential of -0.15 V vs. reversible hydrogen electrode, the Pt/octapod network-based electrodes display a Pt mass activity on the HER of 166 A mg-1 and 42 A mg-1 in acidic and alkaline media, respectively. These values correspond to turnover frequencies of 168 s-1 and 42 s-1, respectively, which are in that order 14 and 21 times higher compared to commercially available Pt/C benchmarks. The strong chemical and mechanical interactions between the Pt and the octapod surface, along with pod-aided adhesion of the Pt/octapod network to the buckypaper, result in a long-term durability (>20 h) of the HER-activity in both media. These results experimentally prove that the exploitation of our network of branched nanocrystals hosting Pt particles can circumvent the durability issues of the catalysts while adopting either ultralow Pt loadings or benchmarking carbon-supported Pt nanocrystals. Our work opens up prospects for using porous networks made by branched nanocrystals as catalysts with ultralow amount of noble metals and controlled catalytic properties.
سجل دخول لتتمكن من نشر تعليقات
التعليقات
جاري جلب التعليقات
سجل دخول لتتمكن من متابعة معايير البحث التي قمت باختيارها
