Study On Controlled Preparation Of Two-dimensional Semiconductor Photocatalytic Materials And Photocatalytic Splitting Water

At this stage,people mainly obtain energy through the combustion of fossil fuels.However,this way of obtaining energy have generated a large amount of harmful substances such as sulfur oxides,nitrogen oxides and dust,which will cause irreversible damage to our living environment.At this point,finding new green and sustainable energy has become an urgent task.Hydrogen energy has many advantages,such as large calorific value and only H2O.In recent years,the technology of photocatalytic cracking of water to produce hydrogen has continuously emerged and has grown rapidly,and has become the focus of attention of scientific researchers.Photocatalytic technology uses semiconductor nanomaterials as catalysts,which can turn a steady stream of solar energy into chemical energy through redox reactions.Therefore,it is regarded as an ideal and most promising strategy to solve the environmental and energy reserve crisis.In this paper,we have selected three traditional semiconductor photocatalytic materials:graphite-phase carbon nitride（g-C₃N₄）,wurtzite cadmium sulfide（CdS）,and anatase titanium dioxide（TiO₂）.Surface exposure and element doping modification methods to solve their narrow photoexcitation range and short photo-generated electron lifetime,etc.,and use visible light to catalyze the cracking of hydrogen to produce hydrogen as a probe to evaluate these modification strategies for their photocatalysis.Performance improvement effect.The main work includes the following contents:（1）Developing a strategy to prepare 1-pyrenebutyrate acid（Py-COOH）modified ultrathin g-C₃N₄ nanosheets（g-C₃N₄-Py）and investigated the excellent photocatalytic H₂ production enhancement of Py-COOH in g-C₃N₄.During the preparation process,the bulk g-C₃N₄ can be exfoliated and noncovalent modified by Py-COOH.The experimental results show that the UV-vis absorption spectrum of g-C₃N₄ shows a significant red shift phenomenon,indicating that this modification strategy can improve the visible-light absorption capacity of g-C₃N₄.Its band gap was reduced from 2.54 eV to 2.43 eV,indicating that the introduction of Py-COOH can significantly reduce g-C₃N₄and thus increase the separation efficiency of photogenerated electrons and holes.In this work,the as-synthesized g-C3N4-Py presents a high H2 production of ca.932.1μmolh^-1g^-1,nearly threefold higher than bulk g-C3N4,thereby proving the unique synergistic effect of Py-COOH in g-C3N4.（2）2D wurtzite CdS nanosheets（HWCs）with（110）and（112）exposed crystal planes were prepared using a water bath heating strategy.The experimental results show that compared with the conventional CdS,the visible light response region of the HWCs photocatalytic material by exposing the（110）and（112）crystal planes is enlarged from560 nm to 590 nm,and the corresponding band gap width is also reduced from 2.31 eV to 2.12 eV,indicating that（110）and（112）crystal plane strategy exposure can significantly improve the CdS response to visible light.Through photoluminescence,transient fluorescence,and electron paramagnetic resonance wave tests,it was found that light-excited electrons and holes will undergo an orderly migration between the（110）and（112）crystal planes,and eventually improve the Separation efficiency.Therefore,the prepared HWCs have excellent visible light splitting capacity to produce H₂ up to about 6214.5μmolh^-1g^-1,which is 5 times the performance of unmodified CdS.（3）Preparing an efficient Sb-N donor-acceptor pairs doping strategy to enhance the H₂ production of anatase TiO₂.During the hydrothermal treatment of massive TiO₂,the massive TiO2 became tiny particles,and the specific surface area and pore volume were enlarged by 4 times and 3 times,respectively.Sb/N atoms could occupy Ti/O sites of TiO2 respectively and act as donor-acceptor pair,thereby reducing the band gap of TiO2from 3.11 to 2.98 eV and preventing charge carriers recombination significantly.The as obtained Sb and N co-doped anatase TiO2（Sb/N-TiO2）shows a high solar-light H2production of ca.2330μmolh^-1g^-1,which is far more higher than single N-or Sb-doped TiO₂(ca.191.7 or 470μmolh^-1g^-1,respectively),directing proofing the excellent synergistic effect of Sb and N in TiO₂.