The Preparation Of Dye-sensitized G-C₃N₄/M/GO Ternary Composites And The Research In Visible-light-driven Hydrogen Production

Developing renewable clean energy is urgent due to the fossil energy crisis.Hydrogen energy is an ideal energy carrier because of its cleanliness and high thermal combustion value.Fossil energy reforming,electrocatalytic water reduction and photocatalytic water reduction are three common methods for hydrogen production.Among these methods,photocatalytic technology shows great application prospects due to using abundant solar energy.Thus,the key to determine whether photocatalytic hydrogen production can be applied depends on designing high performance photocatalysts.Graphitic carbon nitride?g-C₃N₄?as a two-dimensional layered semiconductor material has some unique advantages,including low cost and high light absorption coefficient.However,the high carrier recombination rate and the limited visible absorption?<460nm?have limited the hydrogen production performance of g-C₃N₄.At the same time,loading noble metal Pt cocatalyst is necessary to improve the rate of hydrogen production.Aiming at the problems of easier carrier recombination and limited visible light absorption,this article combine graphene oxide?GO?with g-C₃N₄,which lead to restrain g-C₃N₄ photogenerated carrier recombination.In addition,visible light absorption of g-C₃N₄ was extended by Eosin Y dye sensitization.The amount of noble metal Pt was reduced by loading PtNi and PtCo alloy cocatalyst.The research contents are as follows:?1?The separation efficiency of charge carrier and the visible light absorbance of g-C₃N₄ was increased by the intercalation of GO and Eosin Y sensitization,and thereby the visible-light-responding photocatalytic hydrogen production was improved apparently.The noble metal Pt cocatalyst was reduced in situ on g-C₃N₄ by NaBH₄ and combined with GO through high-power ultrasonic recombination method.The effects of different kinds of xanthene dyes,the mass ratio of dye/catalyst,the mass ratio and complex method of g-C₃N₄/GO on the hydrogen performance of g-C₃N₄/Pt/GO were studied.In Eosin Y-sensitized system,the visible light hydrogen evolution activity for the best photocatalyst g-C₃N₄/Pt/GO was up to 3.82mmol/g/h when the mass ratio of dye/catalyst is 1:1 and g-C₃N₄/GO is 2:1,respectively.The highest apparent quantum yield was 9.7%in the wavelength of 420 nm.Compared to Eosin Y sensitized binary g-C₃N₄/Pt and GO/Pt samples,the H₂ evolution increased by 2.1 and 7.7 times,respectively.Eosin Y sensitization increases the absorption of visible light to about 600 nm,the GO interpolation not only increases the adsorption capacity of Eosin Y,but also promotes the separation of photogenerated electron-hole pairs effectively.?2?The visible-light-responding photocatalytic hydrogen production property was improved further by loading the PtNi or PtCo alloy to substitue the noble metal Pt co-catalyst.PtNi and PtCo cocatalysts were supported using NaBH₄ liquid phase reduction method.The influence of molar ratio and load capacity about Pt/Ni and Pt/Co on visible light hydrogen performance was studied.For PtNi alloy,the best hydrogen production activity of g-C₃N₄/PtNi/GO sample is 5.89 mmol/g/h when Pt/Ni molar ratio is 1:1 and the loading amount is0.5%.Compared with g-C₃N₄/Pt/GO sample under the same conditions,the hydrogen production performance increased by 1.54 times.For PtCo alloy,the best hydrogen production activity is up to 5.05 mmol/g/h when Pt/Co molar ratio is 1:3 and the loading amount is 1%.Compared with g-C₃N₄/Pt/GO sample,the hydrogen production performance increased by 1.32 times.The reasons in improving the hydrogen production performance of alloy cocatalysts lies in the great dispersibility of catalysts and the increase of active positions,which are beneficial to the separation of the photogenerated carrier.