S-Scheme异质结光催化产氢研究进展（英文）

随着不可再生能源的大量消耗,能源短缺成为人类社会面临的重大挑战。在众多新能源制备技术中,光催化分解水制氢技术只需丰富的太阳能作为驱动力就可以实现分解水制氢,且制氢条件温和、绿色无污染,被认为是解决当前能源短缺危机的有效技术之一。光催化制氢技术的核心是光催化剂,因此发展高效稳定的光催化剂至关重要。然而,单组分光催化剂由于空穴-电子复合速度快、氧化还原能力有限、太阳能利用效率低等原因,通常只能呈现出有限的光催化分解水制氢活性。为此,科研人员做了大量改性研究,其中常见的改性策略有元素掺杂、助催化剂修饰、构建异质结等。通常,元素掺杂、助催化剂修饰等改性手段可以在一定程度上提高光催化剂的制氢活性,但并不能有效解决单相光催化剂的缺陷,导致其改性效果受到制约。然而,在两个或多个半导体之间构建异质结可以有效解决上述单组分光催化剂的缺陷。相较于当前流行的传统II型异质结和Z-型异质结,S-型异质结的电荷转移机制更为合理,受到科学家们的广泛关注与应用。因此,本文首先对S-型异质结光催化体系的发展背景进行介绍,包括传统II型异质结、全固态Z-型异质结和液相Z-型异质结光催化系统。随后对S-型异质结光催化机理...     

构建NiS2/MoSe2 S型异质结高效光催化产氢

S-scheme heterojunction is a major breakthrough in the field of photocatalysis. In this study, NiS₂ and MoSe₂ were prepared by a typical solvothermal method, and compounded by an in situ growth method to construct an S-scheme heterojunction. The obtained composite showed excellent performance in photocatalytic hydrogen evolution; the hydrogen production rate was approximately 7 mmol·h^-1·g^-1, which was 2.05 times and 2.44 times those of pure NiS₂ and MoSe₂, respectively. Through a series of characterizations, it was found that NiS₂ and MoSe₂ coupling can enhance the light absorption intensity, which is vital for the light reaction system. The efficiency of electron-hole pair separation is also among the important factors restricting photocatalytic reactions. Compared with pure NiS₂ and MoSe₂, NiS₂/MoSe₂ exhibited a higher photocurrent density, lower cathode current, and lower electrochemical impedance, which proves that the NiS₂/MoSe₂ complex can effectively promote photogenerated electron transfer. Simultaneously, the lower emission intensity of fluorescence indicated effective inhibition of electron-hole recombination in the NiS₂/MoSe₂ complex, which is favorable for the photocatalytic hydrogen evolution reaction. Further, scanning electron microscopy (SEM) and transmission electron microscopy (TEM) showed that MoSe₂ is an amorphous sample surrounded by the NiS₂ nanomicrosphere, which greatly increased the contact area between the two, thus increasing the active site of the reaction. Secondly, as a photosensitizer, Eosin Y (EY) effectively enhanced the absorption of light by the catalyst in the photoreaction system. Meanwhile, during sensitization, electrons were provided to the catalyst, which effectively improved the photocatalytic reaction efficiency. The establishment of S-scheme heterojunctions contributed to improving the redox capacity of the reaction system and was the most important link in the photocatalytic hydrogen reduction of aquatic products. It was also the main reason for the improvement of the hydrogen evolution effect in this study. The locations of the conduction band and valence band of NiS₂ and MoSe₂ were determined by Mott-Schottky plots and photon energy curves, and further proved the establishment of the S-scheme heterojunction. This work provides a new reference for studying the S-scheme heterojunction to effectively improve the photocatalytic hydrogen production efficiency.      

石墨烯修饰三氧化钨/二氧化钛S型异质结增强的光催化产氢活性（英文）

太阳光驱动的光催化分解水产氢是利用太阳能解决当前能源危机和环境问题的理想策略.二氧化钛由于其稳定、环境友好和成本低等优点受到广泛研究,在光催化领域具有不可或缺的作用.然而,纯二氧化钛光催化剂具有光生电子-空穴复合率高、太阳能利用率低等缺点,使其在光催化产氢领域的应用受到限制.迄今为止,人们探索了多种改性策略来提高二氧化钛的光催化活性,如贵金属负载、金属或非金属元素掺杂、构建异质结等.通过复合两个具有合适能带排布的半导体来构建异质结可以大大提高光生载流子的分离,被认为是一种有效的解决方案.最近提出了一种新的S型异质结概念,以解释不同半导体异质界面载流子转移分离的问题.S型异质结是在传统Ⅱ型和Z型(液相Z型、全固态Z型、间接Z型、直接Z型)基础上提出的,但又扬长避短,优于传统Ⅱ型和Z型.通常,S型异质结是由功函数较小、费米能级较高的还原型半导体光催化剂和功函数较大、费米能级较低的氧化型半导体光催化剂构建而成.三氧化钨禁带宽度较小(2.4-2.8 eV),功函数较大,是典型的氧化型光催化剂,也是构建S型异质结的理想半导体光催化剂.根据S型电荷转移机制,三氧化钨/二氧化钛复合物在光辐照下,三氧化钨导带上相对无用的电子与二氧化钛价带上相对无用的空穴复合,二氧化钛导带上还原能力较强的电子和三氧化钨价带上氧化能力较强的空穴得以保留,从而在异质界面上实现了氧化还原能力较强的光生电子-空穴对的分离.同时,石墨烯作为一种蜂窝状碳原子二维材料,是理想的电子受体,在异质结光催化剂中能及时转移电子.而且,石墨烯具有较好的导热性和电子迁移率,光吸收强,比表面积大,可为光催化反应提供丰富的吸附和活性位点,已经被认为是一种重要催化剂载体和光电分解水产氢的有效共催化剂.本文采用简便的一步水热法制备石墨烯修饰的三氧化钨/二氧化钛S型异质结光催化剂.光催化产氢性能测试表明,三氧化钨/二氧化钛/石墨烯复合材料的光催化产氢速率显著提高(245.8μmol g^-1 h^-1),约为纯TiO2的3.5倍.高分辨透射电子显微镜、拉曼光谱和X射线光电子能谱结果证明了TiO2和WO3纳米颗粒的紧密接触,并成功负载在还原氧化石墨烯(rGO)上.X射线光电子能谱中Ti 2p结合能的增加证实TiO2和WO3之间强的相互作用和S型异质结的形成.此外,复合材料中的rGO大大拓展了复合物的光吸收范围(紫外-可见漫反射光谱),增强了光热转换效应,而且rGO与TiO2之间形成肖特基结,促进了TiO2导带电子的转移和分离.总之,WO3和TiO2的S型异质结与TiO2和rGO之间的肖特基异质结的协同效应抑制了相对有用的电子和空穴的复合,有利于氧化还原能力较强的载流子的分离和进一步转移,加速了表面产氢动力学,于是增强了三元复合光催化剂的光催化产氢活性.     

新型光催化异质结:S型异质结

太阳能是最丰富的清洁和可再生能源,光催化技术在太阳能利用中具有很大潜力,这有赖于高效半导体光催化剂的设计制备.然而,单一光催化剂效率很低,主要是光生电子和空穴的强库伦吸引力导致它们快速复合.此外,单一光催化剂也很难同时具有宽光谱吸收和足够的氧化还原能力.为了解决这一问题,构建异质结光催化剂成为一种有效途径,因为它可以实现光生电子和空穴在空间上的有效分离.针对传统的Ⅱ型和Z型异质结在动力学和热力学方面的缺陷,2019年由武汉理工大学余家国教授团队提出梯形异质这一新型异质结概念.对于Ⅱ型异质结,热力学和动力学分析表明光生载流子的转移机理不正确.热力学和动力学分析表明光生载流子的转移机理不正确.而Z型异质结系统主要包括传统、全固态和直接Z型异质结三种类型.对于前两种异质结,它们的界面电子转移存在理论问题.传统Z型异质结利用氧化还原电对,而电子受体和给体更容易从与其具有较大的电势差的半导体接受或给予电子.全固态Z型异质结利用导体,比如导电金属或碳材料,取代氧化还原电对,从而使其应用范围由液态扩展到固态.然而通过进一步分析,它的电荷传输也有漏洞.首先,界面的肖特基势垒抑制电荷持续传输,此外,全固态Z型异质结中的导体与传统Z型中氧化还原电对的作用如出一辙.因此,传统Z型的问题在这里也依旧存在.总的来说,Ⅱ型、传统和全固态Z型都面临相同的问题,就是光生电子和空穴拥有较弱的还原和氧化能力,而S型异质结则与它们截然不同.该异质结由氧化型和还原型光催化剂组成,内建电场、能带弯曲和库仑力三大作用促使氧化型的光生电子与还原型的光生空穴复合,同时阻止氧化型的光生空穴与还原型的光生电子转移.最终,电子和空穴分别具有高的还原和氧化能力.由于其优越性,S型异质结在各种光催化应用中引起了广泛的兴趣,包括产氢、二氧化碳还原、污染物降解和灭菌等领域.而S型异质结机理可以用X射线光电子能谱、电子顺磁共振和原子力显微镜进行表征.S型异质结崭露头角,未来发展可期.     

新型光催化异质结:S型异质结

太阳能是最丰富的清洁和可再生能源,光催化技术在太阳能利用中具有很大潜力,这有赖于高效半导体光催化剂的设计制备.然而,单一光催化剂效率很低,主要是光生电子和空穴的强库伦吸引力导致它们快速复合.此外,单一光催化剂也很难同时具有宽光谱吸收和足够的氧化还原能力.为了解决这一问题,构建异质结光催化剂成为一种有效途径,因为它可以实现光生电子和空穴在空间上的有效分离.针对传统的Ⅱ型和Z型异质结在动力学和热力学方面的缺陷,2019年由武汉理工大学余家国教授团队提出梯形异质这一新型异质结概念.对于Ⅱ型异质结,热力学和动力学分析表明光生载流子的转移机理不正确.热力学和动力学分析表明光生载流子的转移机理不正确.而Z型异质结系统主要包括传统、全固态和直接Z型异质结三种类型.对于前两种异质结,它们的界面电子转移存在理论问题.传统Z型异质结利用氧化还原电对,而电子受体和给体更容易从与其具有较大的电势差的半导体接受或给予电子.全固态Z型异质结利用导体,比如导电金属或碳材料,取代氧化还原电对,从而使其应用范围由液态扩展到固态.然而通过进一步分析,它的电荷传输也有漏洞.首先,界面的肖特基势垒抑制电荷持续传输,此外,全固态Z型异质结中的导体与传统Z型中氧化还原电对的作用如出一辙.因此,传统Z型的问题在这里也依旧存在.总的来说,Ⅱ型、传统和全固态Z型都面临相同的问题,就是光生电子和空穴拥有较弱的还原和氧化能力,而S型异质结则与它们截然不同.该异质结由氧化型和还原型光催化剂组成,内建电场、能带弯曲和库仑力三大作用促使氧化型的光生电子与还原型的光生空穴复合,同时阻止氧化型的光生空穴与还原型的光生电子转移.最终,电子和空穴分别具有高的还原和氧化能力.由于其优越性,S型异质结在各种光催化应用中引起了广泛的兴趣,包括产氢、二氧化碳还原、污染物降解和灭菌等领域.而S型异质结机理可以用X射线光电子能谱、电子顺磁共振和原子力显微镜进行表征.S型异质结崭露头角,未来发展可期.     

p-n型NiWO4/ZnIn2S4异质结光解水析氢性能

采用水热/水浴两步法构筑了p-n型Ni WO₄(NWO)/Zn In₂S₄(ZIS)异质结,研究了不同含量的NWO对ZIS物相组分、形貌结构、能带结构、光谱吸收及光解水析氢性能等的影响,并采用一系列表征手段探讨了NWO/ZIS异质结的光催化机理.结果表明,负载NWO后,ZIS物相组分及形貌结构未发生显著变化,两种材料界面接触紧密且分布均匀;在可见光辐照下,NWO/ZIS异质结光解水析氢性能得到了显著提升,其中,最佳样品NWO-35/ZIS析氢速率达到5204.8μmol·g^-1·h^-1,为纯相ZIS(1566.4μmol·g^-1·h^-1)的3.32倍;循环实验结果表明,NWO/ZIS样品具有很好的光稳定性;能带结构和光电子动力学表征结果证实了p-n型异质结内建电场驱动的光生载流子的传输机制.     

构建S型异质结COF/CdS以增强太阳光产氢

高效利用太阳能是解决当前能源危机和环境问题的有效途径.光催化制氢技术具有绿色环保、成本低等优势,且氢气可作为能源载体,其燃烧产物仅为水,因此被认为是实现高效利用太阳能的最佳途径之一.为更好地利用太阳能,研究者们致力于开发具有良好可见光活性的光催化剂.CdS因具有良好的电荷转移能力和在可见光区域强吸收的特性,在光催化制氢...     

硫化钴改性石墨炔构建S型异质结高效光催化产氢

石墨炔(GDY,g-CnH2n-2)作为一种新型的由sp和sp2杂化的碳原子构成的二维碳材料,因其独特的纳米级孔隙、二维层状共轭骨架结构及半导体性质等特性,使之在能源、电化学、光催化、光学、电子学等诸多领域具有显著优势.它作为一种具有良好的层状结构的新型碳材料,其可调节的电子结构弥补了石墨烯无明显带隙的缺点,有望在光催...     

2D/2D BiOBr/g-C3N4 S型异质结光催化性能

近年来,能源短缺和环境污染严重威胁人类的可持续发展.光催化技术具有绿色环保、成本低等优势,被认为是解决上述问题的最佳途径之一,其实用化的核心是开发高效可见光催化材料.石墨相氮化碳(g-C3N4)因其物理化学性质稳定、无毒、廉价及能带适宜等特点,广泛应用于光催化领域.然而,光生载流子易复合、比表面积小等问题不利于其实际应...     

Mn0.2Cd0.8S@CoAl LDH S-型异质结构建及其光催化析氢性能研究

构建高效、稳定的异质结光催化剂体系是实现太阳能驱动分解水制氢的有效途径。本研究通过物理混合法将Mn_0.2Cd_0.8S纳米棒与CoAl LDH纳米片进行耦合,成功制备出一种新型的Mn_0.2Cd_0.8S@CoAl LDH (MCCA) S型异质结光催化剂。光致发光光谱和光电流测试结果表明,该异质结在内建电场的作用下可以有效地加快Mn_0.2Cd_0.8S和CoAl LDH界面间光生载流子的分离和电子转移。关键的是,CoAl LDH的引入有效地抑制了光生电子与空穴的复合,从而提高了Mn_0.2Cd_0.8S的光催化产氢活性。最佳CoAl LDH负载量的MCCA-3在5 h内的产氢量为1177.9 μmol。与单独使用纯Mn_0.2Cd_0.8S纳米棒和CoAl LDH纳米片相比,这是一个显著的改进。本研究为合理设计用于光催化制氢的S型异质结光催化剂提供了一条简单有效的途径。     

In2O3修饰三维纳米花MoSx构建S型异质结用于高效光催化产氢

形貌控制和异质结构建是提升光催化剂性能的有效策略。本文采用In₂O₃修饰三维纳米花MoS_x并构建S型异质结,为电子的传输提供了特殊的转移途径。通过合理调控In₂O₃的负载量,MoS_x/In₂O₃的最佳产氢速率能够达到6704.2 μmol∙g⁻¹∙h⁻¹,是纯MoS_x的1.8倍。采用荧光光谱和电化学测试证实复合材料中内部电子和空穴对的分离效率得到了有效的提升,并利用紫外漫反射测试和羟基自由基实验推测了析氢机理。     

原位制备具有增强光催化活性的S型Bi2Se3/g-C3N4光催化剂

光催化氧化是一种应用前景良好的环境治理技术.与絮凝、物理吸附和化学氧化等常见的方法相比,光催化氧化具有环境友好、氧化完全、方便和廉价等优势.特别是可见光光催化氧化,可利用太阳能中占比最高的可见光,在应用中更具优势.因而,探索可见光响应性能优异的光催化剂一直是光催化氧化领域的一个重要研究内容.硒化铋(Bi₂Se₃)是一种带隙(带隙宽度在0.3~1.3 e V)非常窄的半导体,能吸收全部波长范围的可见光和近红外光.此外,Bi₂Se₃还具有独特的金属表面态,其表面具有良好的导电性.这些特性使其在可见光光催化氧化领域具有很大的应用潜力.然而,由于Bi₂Se₃价带位置高,氧化能力很弱,其价带上的空穴在光催化反应中难以被消耗,导致空穴大量累积,并迅速与光生电子复合,大幅降低了Bi₂Se₃的光催化性能.因此,一直以来,Bi₂Se₃很少被用于光催化反应.如何充分利用Bi₂Se₃的光响应优势,制备出性能优异的光催化剂,仍是具有挑战性和吸引力的研究方向.本文采用预先制备的Bi2O3/g-C₃N₄复合物作为前驱体,通过原位转化的方法,将前驱体置于热的Se蒸汽中,使前驱体上的Bi2O3与Se蒸汽反应,完全转化为Bi₂Se₃纳米颗粒,从而制得Bi₂Se₃/g-C₃N₄复合光催化剂(Bi₂Se₃含量约为4 wt%).透射电镜结果表明,所形成的Bi₂Se₃纳米颗粒较均匀地分布在g-C₃N₄表面.表面功函数分析发现,Bi₂Se₃与g-C₃N₄结合后,它们的费米能级分别由原来的-0.55和-0.18 e V变为平衡时的-0.22 e V,可形成指向g-C₃N₄的内建电场,有利于形成梯型(S型)异质结.在此基础上,能级位移、荧光分析、结构计算和反应自由基测试等结果表明,Bi₂Se₃和g-C₃N₄之间形成了S型异质结.在可见光光催化降解苯酚的实验中,所制备的Bi₂Se₃/g-C₃N₄复合物的光催化活性明显优于单一的Bi₂Se₃和g-C₃N₄.结合比表面、孔结构、光吸收和荧光等对比分析,认为Bi₂Se₃/g-C₃N₄的这种S型异质结构在其光催化活性增强中起到了关键作用.在光照条件下,其g-C₃N₄导带中光生电子向Bi₂Se₃的价带迁移,并与光生空穴复合,从而使Bi₂Se₃导带上可保留更多的高活性光生电子参与光催化反应,由此Bi₂Se₃/g-C₃N₄的光催化活性增强.循环性能测试和光还原实验结果表明,所制备的Bi₂Se₃/g-C₃N₄复合光催化剂具有良好的稳定性.本文工作为高可见光吸收的光催化剂制备和性能增强提供了新途径和新视野.     

Construction of CoS2/Zn0.5Cd0.5S S-Scheme Heterojunction for Enhancing H2 Evolution Activity Under Visible Light

In the field of photocatalysis, building a heterojunction is an effective way to promote electron transfer and enhance the reducibility of electrons. Herein, the S-scheme heterojunction photocatalyst (CoS₂/Zn_0.5Cd_0.5S) of CoS₂ nanospheres modified Zn_0.5Cd_0.5S solid solution was synthesized and studied. The H₂ evolution rate of the composite catalyst reached 25.15 mmol g⁻¹ h⁻¹, which was 3.26 times that of single Zn_0.5Cd_0.5S, whereas pure CoS₂ showed almost no hydrogen production activity. Moreover, CoS₂/Zn_0.5Cd_0.5S had excellent stability and the hydrogen production rate after six cycles of experiments only dropped by 6.19 %. In addition, photoluminescence spectroscopy and photoelectrochemical experiments had effectively proved that the photogenerated carrier transfer rate of CoS₂/Zn_0.5Cd_0.5S was better than CoS₂ or Zn_0.5Cd_0.5S single catalyst. In this study, the synthesized CoS₂ and Zn_0.5Cd_0.5S were both n-type semiconductors. After close contact, they followed an S-scheme heterojunction electron transfer mechanism, which not only promoted the separation of their respective holes and electrons, but also retained a stronger reduction potential, thus promoting the reduction of H⁺ protons in photocatalytic experiments. In short, this work provided a new basis for the construction of S-scheme heterojunction in addition to being used for photocatalytic hydrogen production.     

微波辅助快速制备2D/1D ZnIn2S4/TiO2 S型异质结及其光催化制氢性能

The threat and global concern of energy crises have significantly increased over the last two decades. Because solar light and water are abundant on earth, photocatalytic hydrogen evolution through water splitting has been considered as a promising route to produce green energy. Therefore, semiconductor photocatalysts play a key role in transforming sunlight and water to hydrogen energy. To date, various photocatalysts have been studied. Among them, TiO₂ has been extensively investigated because of its non-toxicity, high chemical stability, controllable morphology, and high photocatalytic activity. In particular, 1D TiO₂ nanofibers (NFs) have attracted increasing attention as effective photocatalysts because of their unique 1D electron transfer pathway, high adsorption capacity, and high photoinduced electron–hole pair transfer capability. However, TiO₂ NFs are considered as an inefficient photocatalyst for the hydrogen evolution reaction (HER) because of their disadvantages such as a large band gap (~3.2 eV) and fast recombination of photoinduced electron–hole pairs. Therefore, the development of a high-performance TiO₂ NF photocatalyst is required for efficient solar light conversion. In recent years, several strategies have been explored to improve the photocatalytic activity of TiO₂ NFs, including coupling with narrow-bandgap semiconductors (such as ZnIn₂S₄). Recently, microwave (MW)-assisted synthesis has been considered as an important strategy for the preparation of photocatalyst semiconductors because of its low cost, environment-friendliness, simplicity, and high reaction rate. Herein, to overcome the above-mentioned limiting properties of TiO₂ NFs, we report a 2D/1D ZnIn₂S₄/TiO₂ S-scheme heterojunction synthesized through a microwave (MW)-assisted process. Herein, the 2D/1D ZnIn₂S₄/TiO₂ S-scheme heterojunction was constructed rapidly by using in situ 2D ZnIn₂S₄nanosheets decorated on 1D TiO₂ NFs. The loading of ZnIn₂S₄ nanoplates on the TiO₂ NFs could be easily controlled by adjusting the molar ratios of ZnIn₂S₄ precursors to TiO₂ NFs. The photocatalytic activity of the as-prepared samples for water splitting under simulated solar light irradiation was assessed. The experimental results showed that the photocatalytic performance of the ZnIn₂S₄/TiO₂ composites was significantly improved, and the obtained ZnIn₂S₄/TiO₂ composites showed increased optical absorption. Under optimal conditions, the highest HER rate of the ZT-0.5 (molar ratio of ZnIn₂S₄/TiO₂= 0.5) sample was 8774 μmol·g^-1·h^-1, which is considerably higher than those of pure TiO₂ NFs (3312 μmol·g^-1·h^-1) and ZnIn₂S₄nanoplates (3114 μmol·g^-1·h^-1) by factors of 2.7 and 2.8, respectively. Based on the experimental data and Mott-Schottky analysis, a possible mechanism for the formation of the S-scheme heterojunction between ZnIn₂S₄ and TiO₂ was proposed to interpret the enhanced HER activity of the ZnIn₂S₄/TiO₂heterojunctionphotocatalysts.      

Rapid Charge Transfer Endowed by Interfacial Ni-O Bonding in S-scheme Heterojunction for Efficient Photocatalytic H2 and Imine Production

Cooperative coupling of H₂ evolution with oxidative organic synthesis is promising in avoiding the use of sacrificial agents and producing hydrogen energy with value-added chemicals simultaneously. Nonetheless, the photocatalytic activity is obstructed by sluggish electron-hole separation and limited redox potentials. Herein, Ni-doped Zn_0.2Cd_0.8S quantum dots are chosen after screening by DFT simulation to couple with TiO₂ microspheres, forming a step-scheme heterojunction. The Ni-doped configuration tunes the highly active S site for augmented H₂ evolution, and the interfacial Ni−O bonds provide fast channels at the atomic level to lower the energy barrier for charge transfer. Also, DFT calculations reveal an enhanced built-in electric field in the heterojunction for superior charge migration and separation. Kinetic analysis by femtosecond transient absorption spectra demonstrates that expedited charge migration with electrons first transfer to Ni²⁺ and then to S sites. Therefore, the designed catalyst delivers drastically elevated H₂ yield (4.55 mmol g⁻¹ h⁻¹) and N-benzylidenebenzylamine production rate (3.35 mmol g⁻¹ h⁻¹). This work provides atomic-scale insights into the coordinated modulation of active sites and built-in electric fields in step-scheme heterojunction for ameliorative photocatalytic performance.     

MoS2 as a Co-Catalyst for Photocatalytic Hydrogen Production: A Mini Review

Molybdenum disulfide (MoS₂), with a two-dimensional (2D) structure, has attracted huge research interest due to its unique electrical, optical, and physicochemical properties. MoS₂ has been used as a co-catalyst for the synthesis of novel heterojunction composites with enhanced photocatalytic hydrogen production under solar light irradiation. In this review, we briefly highlight the atomic-scale structure of MoS₂ nanosheets. The top-down and bottom-up synthetic methods of MoS₂ nanosheets are described. Additionally, we discuss the formation of MoS₂ heterostructures with titanium dioxide (TiO₂), graphitic carbon nitride (g-C₃N₄), and other semiconductors and co-catalysts for enhanced photocatalytic hydrogen generation. This review addresses the challenges and future perspectives for enhancing solar hydrogen production performance in heterojunction materials using MoS₂ as a co-catalyst.     

Chlorophyll-Based Organic Heterojunction on Ti3C2Tx MXene Nanosheets for Efficient Hydrogen Production

The Z-scheme process is a photoinduced electron-transfer pathway in natural oxygenic photosynthesis involving electron transport from photosystem II (PSII) to photosystem I (PSI). Inspired by the interesting Z-scheme process, herein a photocatalytic hydrogen evolution reaction (HER) employing chlorophyll (Chl) derivatives, Chl-1 and Chl-2, on the surface of Ti₃C₂T_x MXene with two-dimensional accordion-like morphology, forming Chl-1@Chl-2@Ti₃C₂T_x composite, is demonstrated. Due to the frontier molecular orbital energy alignments of Chl-1 and Chl-2, sublayer Chl-1 is a simulation of PSI, whereas upper layer Chl-2 is equivalent to PSII, and the resultant electron transport can take place from Chl-2 to Chl-1. Under the illumination of visible light (>420 nm), the HER performance of Chl-1@Chl-2@Ti₃C₂T_x photocatalyst was found to be as high as 143 μmol h⁻¹ g_cat⁻¹, which was substantially higher than that of photocatalysts of either Chl-1@Ti₃C₂T_x (20 μmol h⁻¹ g⁻¹) or Chl-2@Ti₃C₂T_x (15 μmol h⁻¹ g⁻¹).