类贵金属/硫化钼/碳基复合电极的结构设计及电解水析氢协同增强机制研究

Because the overuse of fossil fuels to intensify air pollution and global warming, sustainable hydrogen production is an essential prerequisite. Great efforts have been devoted to water electrolysis, which provides a promising avenue because it is possible to produce hydrogen by renewable resource-derived electricity. Among many things, the hydrogen evolution reaction (HER) on cathode in water electrolysis requires highly active electrocatalysts to make the water splitting process more energy-efficient and economical. To date, Pt-group metals are the state-of-the-art catalysts in HER with low onset potential (nearly zero) and large current density in acid solution. However, their widespread applications for HER have been limited by their low earth-abundance and high costs. There are still great interests to develop highly efficient and cost-effective electrocatalysts using earth-abundant elements. Among these materials, molybdenum chalcogenides (MoS2), widely used as hydrodesulfurization (HDS) catalysts in the petroleum industry, have received special attention due to the close free energy of adsorbed atomic hydrogen with that of Pt-group metals. However, low conductivity, limited surface area, and the inert two-dimensional MoS2 surface make it challenging to obtain high HER performance. This proposal focuses on a novel strategy to utilize electrostatic self-assembly between long-chain ammonium cations (such as cetyltrimethylammonium cations, dodecyltrimethylammonium cations, et al.) and tetrathiomolybdate anions to form surfactant-encapsulated Mo-clusters in acidic aqueous solution, where mono-dispersed surfactant-encapsulated Mo-clusters in water phase with a uniform size will be synthesized. Particle size and structure of surfactant-encapsulated Mo-clusters are finely turned by changing composition and preparation conditions in order to improve hydrothermal stability. After that, a new synthetic route was developed to fabricate the precursors of noble metal-like promoters/molybdenum sulfides/carbonitride nanomaterials by polymerization reaction, which will confine the surfactant-encapsulated Mo-clusters in the carbonitride framework by the optimization of process conditions. Then, subsequent thermal annealing process will be performed to prepare noble metal-like promoters/molybdenum sulfides/carbonitride nanomaterials, such as MoO2/MoSx, Mo2C/MoSx, or MoN/MoSx in different atmosphere in order to enhance the synergistic effects by in-situ transformation from the Mo-based precursors. Extensively physicochemical characterizations of the synthesized noble metal-like promoters/molybdenum sulfides/carbonitride nanomaterials are carried out. The performances of hydrogen evolution reaction are explored on the synthesized catalysts. Efforts will also be directed to demonstrating the synergistic effects between noble metal-like promoters and molybdenum sulfides, understanding the structure-performance relationship between composition, active phase structure (including dispersion, MoS2 slab length and stacking layer number) and the HER performance, reaction mechanism as well as reaction kinetics. This work addresses novel strategies for preparation of advanced molybdenum sulfides catalysts, providing an insightful guidance for developing novel and efficient cathodic catalysts for water electrolysis.

本项目针对电解水制氢阴极非贵金属硫化钼片晶稳定性差易堆垛、活性位点与导电性不足等关键科学问题，运用超分子组装的思想和借助超声分散的手段系统研究表面活性剂包覆多钼硫簇溶胶粒子尺寸的控制方法，实现活性相尺寸的精细调变；优化碳基前驱体的聚合参数，对包覆型多钼硫簇纳米粒子进行分散隔离；研究后处理方法（包括热/等离子体技术）对类贵金属/硫化钼/碳基复合材料的组成、结构的影响规律，实现类贵金属的原位生长，硫化钼分散度、堆垛度、长度的调控及惰性晶面的活化，在碳层保护下提高稳定性和电子转移速率。针对电解水析氢反应，综合多种理化表征和第一性原理理论计算研究催化剂组成、结构对析氢性能的影响规律，揭示析氢性能（析氢电位、反应途径、动力学参数等）与催化剂结构（硫化钼片晶长度、堆垛度、分散度）的构效关系，弄清类贵金属与硫化钼间的协同机制，解析析氢反应的机理和动力学，为硫化钼催化剂的改造、优化和创新提供启示和指导。

采用太阳能、风能等产生的电能为动力驱动的电解水制氢是富有前景的新能源解决方案之一，由于电解水制氢需要在过电压下发生，实际操作时需增加反应的槽电压，这无疑增加了能耗与成本。作为新兴的非贵金属电催化剂，硫化钼纳米催化剂是近年来研究的热点，在纳米尺度上进行催化剂的结构设计与优化是获得高性能析氢催化剂的关键。本项目按照计划执行，完成设定的研究目标。主要包括：① 通过聚合反应和热处理结合的方法成功合成了类贵金属氮化钼掺杂硫化钼/碳氮复合纳米材料，从而改善了材料的电子结构，提高了本征导电性；② 提出了一种有效的策略合成了MoS2阵列/MoO2/MF自支撑电极，密度泛函理论(DFT)计算揭示了MoO2薄膜和MoS2纳米阵列之间强相互作用可以有效提高材料的导电性、减小MoS2的能带间隙和优化H吸附自由能，加快了HER动力学过程；③ 将非贵金属钴掺杂到硫化钼晶型中形成了具有丰富CoMoS相的硫化钼纳米片，深入探讨了其优异活性位的起源；④ 构建了异质结构CoP阵列/MoO2/MF自支撑电极对碱性条件下析氧反应，DFT计算表明CoP和MoO2间存在强的协同作用，加快了Volmer和Heyrovsky反应，揭示了优异电催化性能的反应本质；⑤ 拓展研究了Ni、Fe、Co基系列电解水阳极析氧催化剂，变出优异的全解水制氢性能。⑥ 项目共发表标注论文20篇、申请相关专利1件；参加了第十八届全国催化学术会议（天津）、第十一届全国环境催化与环境科学会议（沈阳）、第十九届全国催化学术会议（重庆）、The 1th International Conference on Advanced Functional Materials（杭州）等。⑦ 项目执行期间，培养研究生10名（包括3名博士研究生），其中4名研究生已经获得学位，3人获得国家奖学金，2人获得校级优秀毕业生。