Photocatalytic production of H2 from the decomposition of water has attracted increased attention, as the environmental damages caused by the rapid evolution of industry are threatening the development of human society. This energy production is considered a green and eco-friendly resource. It has the potential to replace the carbon component of fuelling the society; on the other hand allows for the limitation of greenhouse gas emissions, thereby mitigating the worsening of climate change. While titanium dioxide is widely used in the photocatalytic field, its yield is still low due to the fast recombination of the photo-generated charge carriers. Graphitic carbon nitride (g-C3N4) possessing high thermal and chemical stability, non-toxicity and low band gap energy is a promising candidate for photocatalytic applications. In this study the exfoliation of the bulk g-C3N4 made with melamine was synthesised via a chemical approach using nitric acid at room temperature, in order to get prolonged carrier lifetime. Moreover the surface of bulk g-C3N4 made with melamine and urea and the exfoliated g-C3N4 made with melamine was modified with graphene (0.5 wt% and 1 wt%). Hydrogen generation from methanol/water mix proved that only hydrogen was produced in the unmodified bulk and exfoliated g-C3N4 , while H2, CH4 and CO have been generated in the modified specimens with graphene. This was assigned to the increased spatial charge carrier separation conducted by graphene.
Clean energy, as well as air and water pollution, have become key challenges in today's society. Photocatalysis could be one of the ways to address them. It is considered as an advanced oxidation method that involves light to activate a semiconductor. Semiconductors based on titanium dioxide (TiO2) are widely regarded as photocatalytically active materials. However, the performance of TiO2 has limitations due to its wide band gap (~3.2 eV), and a high recombination rate of the photo-generated electron-hole (e−−h+) pair. To overcome these drawbacks, TiO2 in heterojunction with tungsten trioxide (WO3) is well recognized as one of the most explored systems for photocatalytic applications. Depending on the synthesis technique, and the photocatalytic application, various yet contrasting behaviour can be found in the literature. In this work, the photocatalytic properties of the TiO2/WO3 system were thoroughly examined in the removal of gaseous benzene, and generation of H2. Graphene nanoplatelets were included into the TiO2/WO3 system to increase transport and life-time of the photo-generated exciton. The investigation of various parameters that affected the photocatalytic activity of synthesised materials were carried out, including the ratio of WO3 to TiO2, the presence of graphene, and the nature of the photocatalytic application. It has been observed that the position of the conduction bands played indeed a key-role in case of hydrogen generation. A type II heterojunction was found in the TiO2/WO3 system. Modification of TiO2/WO3 with graphene nanoplatelets improved the photocatalytic hydrogen generation, which was particularly evident in samples with higher WO3 content. The most significant increase in hydrogen production was observed with the photocatalyst with 15 mol% WO3 and 1 wt% graphene − a five-fold increase in yield, compared to its counter-part with no graphene.
Graphitic carbon nitride (g-C3N4) possessing high thermal and chemical stability, non-toxicity, facile synthesis, and low band gap energy is a promising candidate for photocatalytic applications. In this study, bulk and...
In today's society, air and water pollution, as well as clean energy, have become major concerns. Photocatalysis could be one of the ways used to address this new set of problems. Photocatalysis is a type of advanced oxidation method that involves light to activate a semiconductor. The semiconductor materials most likely to generate these reactions are titanium dioxide-based. However, TiO2 has its drawbacks, as light absorption limited to the UVA region of the solar radiation due to its wide band-gap (~3.2 eV), and a high rate of photogenerated electron-hole recombination in the photocatalyst. To address those problems, the sol-gel process was adopted for the synthesis of TiO2 nanoparticles, and TiO2 heterojunction with WO3 was carried out to decrease the rate of electron-hole pair recombination and enhance photocatalytic properties. In addition, graphene nanoplatelets were introduced to the TiO2/WO3 system to aid the transport and separation of photogenerated exciton. In this work, various parameters affecting the photocatalytic activity of the synthesized materials were investigated, including the ratio of WO3 to TiO2, the introduction of graphene, and the nature of the photocatalytic application (degradation of gaseous benzene and generation of H2). The structural and optical characteristics, as well as the properties of the adsorption surfaces, were all investigated. It was found that for materials containing more than 10 mol % of WO3, the addition of graphene in to the TiO2/WO3 system appears to boost photocatalytic activity for H2 generation under UV light compared to the TiO2/WO3 system, suggesting the existence of an optimal proportion allowing a greater photocatalytic activity.
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