Engineering of SnO_(2)/TiO_(2) heterojunction compact interface with efficient charge transfer pathway for photocatalytic hydrogen evolution

Fabricating an efficient charge transfer pathway at the compact interface between two kinds of semiconductors is an important strategy for designing hydrogen production heterojunction photocatalysts.In this work,we prepared a compact,stable and oxygen vacancy-rich photocatalyst(SnO_(2)/TiO_(2) heterostructure)via a simple and reasonable in-situ synthesis method.Briefly,SnCl_(2)–2H_(2)O is hydrolyzed on the TiO_(2) precursor.After the pyrolysis process,SnO_(2) nanoparticles(5 nm)were dispersed on the surface of ultrathin TiO_(2) nanosheets uniformly.Herein,the heterojunction system can offer abundant oxygen vacancies,which can act as active sites for catalytic reactions.Meanwhile,the interfacial contact of SnO_(2)/TiO_(2) grading semiconductor oxide is uniform and tight,which can promote the separation and migration of photogenerated carriers.As shown in the experimental results,the hydrogen production rate of SnO_(2)/TiO_(2) is 16.7 mmol h^(-1)g^(-1)(4.4 times higher than that of TiO_(2)),which is owing to its good dynamical properties.This work demonstrates an efficient strategy of tight combining SnO_(2)/TiO_(2) with abundant oxygen vacancies to improve catalytic efficiency.

Fully conversing and highly selective oxidation of benzene to phenol based on MOFs-derived CuO@CN photocatalyst

Developing highly efficient photocatalysts for selective oxidation of benzene to phenol is of great significance. However, it is still challenging to simultaneously achieve high conversion rate and selectivity.Herein, we demonstrate 99.9% of benzene photoconversion and 99.1% of phenol selectivity under the illumination of AM 1.5 for 12 h. For this purpose, an advanced CuO@CN photocatalyst has been fabricated by loading tubular carbon nitride(CN) with CuO nanoparticles thermally polymerized from Cu-based metal-organic frameworks(MOFs). The sluggish photocharge carrier recombination rate and the excellent stability indicate that the as-prepared nanocomposite is an ideal photocatalyst for benzene oxidation application. This work paves a new avenue for designing novel photocatalyst based on MOFs and carbon nitride materials.

S-scheme heterojunction/Schottky junction tandem synergistic effect promotes visible-light-driven catalytic activity

Designing photocatalysts with high light utilization and efficient photogenerated carrier separation for pollutant degradation is one of the important topics for sustainable development.In this study,hierarchical core–shell materialα-Fe_(2)O_(3)@ZnIn_(2)S_(4)with a step-scheme(S-scheme)heterojunction is synthesized by in situ growth technique,and MXene Ti_(3)C_(2)quantum dots(QDs)are introduced to construct a double-heterojunction tandem mechanism.The photodegradation efficiency ofα-Fe_(2)O_(3)@ZnIn_(2)S_(4)/Ti_(3)C_(2)QDs to bisphenol A is 96.1%and its reaction rate constant attained 0.02595 min^(−1),which is 12.3 times that of pureα-Fe_(2)O_(3).Meanwhile,a series of characterizations analyze the reasons for the enhanced photocatalytic activity,and the charge transport path of the S-scheme heterojunction/Schottky junction tandem is investigated.The construction of the S-scheme heterojunction enables the photo-generated electrons ofα-Fe_(2)O_(3)and the holes of ZnIn2S4 to transfer and combine under the action of the reverse built-in electric field.Due to the metallic conductivity of Ti_(3)C_(2)QDs,the photogenerated electrons of ZnIn_(2)S_(4)are further transferred to Ti_(3)C_(2)QDs to form a Schottky junction,which in turn forms a double-heterojunction tandem mechanism,showing a remarkable charge separation efficiency.This work provides a new opinion for the construction of tandem double heterojunctions to degrade harmful pollutants.

C_(3)N_(4)/TiO_(2)二维异质结:高效的表面反应与电荷分离效率

高效的电荷分离和快速的界面反应动力学是决定光催化分解水制氢效率的关键因素.通过采用原位剥离和转化策略,本文设计合成了一种具有优异光催化析氢性能的二维异质结光催化剂-超薄多孔C_(3)N_(4)纳米片负载TiO_(2)纳米晶(HCN/TiO_(2)).结果表明,HCN/TiO_(2)光催化材料具有超薄二维结构、丰富且接触紧密的界面、高度多孔结构和TiO_(2)纳米晶分布均匀的特点.以上结构优势不仅能为HCN/TiO_(2)光催化分解水制氢提供更多的活性中心、促进反应物和生成物的传输,而且极大地提升其光生载流子的分离效率.因此,由于表面反应和光生载流子分离二者协同增强,HCN/TiO_(2)光催化剂(10 mg)在模拟太阳光(AM 1.5)照射条件下的析氢速率可达到282.3μmol h^(-1),表观量子效率在420nm波长处为13.4%.该工作为开发高性能二维异质结材料应用于清洁能源领域提供了一个极具前景的合成策略.

Constructing Pd-N interactions in Pd/g-C_(3)N_(4)to improve the charge dynamics for efficient photocatalytic hydrogen evolution

The formation of chemical bonds between metal ions and their supports is an effective strategy to achieve good catalytic activity.However,both the synthesis of active metal species on a support and control of their coordination environment are still challenging.Here,we show the use of an organic compound to produce tubular carbon nitride(TCN)as a support for Pd nanoparticles(NPs),creating a composite material(NP-Pd-TCN).It was found that Pd ions preferentially bind with the electron-rich N atoms of TCN,leading to strong metal-support interactions that benefit charge transfer from g-C_(3)N_(4)to Pd.X-ray absorption spectroscopy further revealed that the metal-support interactions resulted in the formation of Pd-N bonds,which are responsible for the improvement in the charge dynamics as evidenced by the results from various techniques including photoluminescence(PL)spectroscopy,photocurrent measurements,and electrochemical impedance spectroscopy(EIS).Owing to the good dynamical properties,NP-Pd-TCN was used for photocatalytic hydrogen evolution under visible-light irradiation(λ>420 nm)and an excellent evolution rate of~381μmol·h^(-1)(0.02 g of the photocatalyst)was attained.This work aims to promote a strategy to synthesize efficient photocatalysts for hydrogen production by controllably introducing metal nanoparticles on a support and in the meantime forming chemical bonds to achieve intimate metal-support contact.

Supramolecular precursor derived loofah sponge-like Fe_(2)O_(x)/C for effective synergistic reaction of Fenton and photocatalysis

Fenton or photocatalytic degradations of organic contaminants are recognized as promising approaches to address the increasing environmental pollution issues.Herein,we develop the effective synergistic catalysis reaction of Fenton and photocatalysis based on a loofah sponge-like Fe_(2)O_(x)/C nanocomposite,which exhibits excellent nitrobenzene photocatalytic degradation property.It is noted that Fe2O3 nanoparticles with surface Fe^(2+) species were encapsulated with an ultrathin carbon layer(denoted as Fe_(2)O_(x)/C)via a supramolecular self-sacrificing template and following thermal treatment process.The experimental results indicated that the thin layer carbon coating not only inhibited the Fe iron leaching from the Fe_(2)O_(x)but also prompted the separation and transferring of electrons–hole pairs.The introduction of Fe_(2)O_(x)/C enables the Fenton reaction to induce a rapid Fe^(2+)/Fe^(3+)cycle,and meanwhile,together with the photocatalytic reaction to produce continuous active substances for the subsequent degradation catalytic reaction without successive H2O2,resulting in the inexpensive and the effective photocatalytic procedure.As a result,100%nitrobenzene(100 mg/L)was degraded and 97%of the organic carbon was mineralized in 90 min using the Fe_(2)O_(x)/C(0.1 g/L)at a low H_(2)O_(2) dosage(0.50 mM),under air mass(AM)1.5 irradiation.Theoretical calculations confirmed that the Fe_(2)O_(x)/C-600 with thin carbon layer promoted the dissociation of H2O2 and the·OH desorption.The synergistic catalysis of this work may provide new ideas for low-cost and more efficient treatment of pollutants.

A facile solution phase synthesis of directly ordering monodisperse FePt nanoparticles

The ordered Pt-based intermetallic nanoparticles(NPs)with small size show superior magnetic or catalytic properties,but the synthesis of these NPs still remains a great challenge due to the requirement of high temperature annealing for the formation of the ordered phase,which usually leads to sintering of the NPs.Here,we report a simple approach to directly synthesize monodisperse ordered L1_(0)-FePt NPs with average size 10.7 nm without further annealing or doping the third metal atoms,in which hexadecyltrimethylammonium chloride(CTAC)was found to be the key inducing agent for the thermodynamic growth of the Fe and Pt atoms into the ordered intermetallic structure in the synthetic process.In particular,10.7 nm L1_(0)-FePt NPs synthesized by the proper amount of CTAC show a coercivity of 3.15 kOe and saturation magnetization of 45 emu/g at room temperature.The current CTAC-assisted synthetic strategy makes it possible to deeply understand the formation of the ordered Pt-based intermetallic NP in solution phase synthesis.