二维“过渡金属-氮-碳”基复合材料的可控制备及双功能电催化全裂解水性能研究

Overall water splitting into hydrogen and oxygen using electrocatalysts has been considered as the most promising technology to solve the energy crisis and development of sustainable hydrogen energy. Currently, Pt-based and Ir-based precious metals are the most efficient electrocatalysts for hydrogen evolution reactions (HERs) and oxygen evolution reactions (OERs), while the high cost and scarcity severely hinder their widespread practical applications. This project aims at developing novel two-dimensional (2D) transition metal-nitrogen-carbon based hybrids with special microstructures and highly exposed active sites as bifunctional electrocatalysts to address the two major hurdles of high cost and limited resources of noble metals. The amount of various precursors and carbonization temperature are tuned to control the specific surface area, pore size distribution, conductivity, and dopant type and content of transition metal-nitrogen atoms in the hybrid, in order to significantly enhance the electrocatalytic activity of the 2D hybrid for both HERs and OERs from overall water splitting in acid media. Furthermore, the active sites and kinetic behaviors of adsorbed H2O species on the surface of hybrid catalyst will be investigated by combining various advanced characterization technologies (XANES, EXAFS, and aberration-corrected TEM), in-situ spectroscopies (in-situ FTIR, in-situ Raman, and in-situ ESR), with DFT calculations. Based on the analysis, the structure-property relationship between the active site and catalytic activity, and the specific reaction mechanism of electrocatalytic overall water splitting for both HERs and OERs will be clarified, and these results will be helpful for further improvement of the catalytic performance of 2D hybrid. This project will provide some new thoughts for design and construction of highly efficient bifunctional nanocarbon-based electrocatalysts, and it has great scientific value.

电催化全裂解水制氢和氧，已被视为改变能源危机以及实现可持续氢能源发展的重要手段。目前，贵金属铂基和铱基材料是具有最高催化活性的产氢和产氧电催化剂，但是贵金属高昂成本和储量稀少极大地限制了其大规模实际应用。本项目提出构建具有特殊微观结构和高比例暴露活性位点的新型二维“过渡金属-氮-碳”基复合材料双功能电催化剂，通过调变多元化前驱体的用量及反应碳化温度来实现对纳米碳复合材料的比表面积、孔径分布、导电性、过渡金属-氮掺杂类型及含量的有效控制，显著提高其在酸性电解质中电催化全裂解水制氢和氧的活性。在此基础上，采用多种先进表征手段、原位谱学技术辅以理论模拟计算，考察催化材料表面的活性位点及吸附态水分子的反应动力学行为，建立材料结构与催化性能之间的构效关系，阐述电催化全裂解水制氢和氧的反应机理。本项目的实施可为设计和构建双功能高效纳米碳基电催化剂提供一个新的思路，具有重要科学价值。

电催化裂解水作为一种绿色，可持续的大规模制氢和氧的方法已经引起了广泛的关注。迄今为止，贵金属Pt和Ir基材料仍然被公认为是最有效的电催化剂，然而这些贵金属材料的稀缺性和昂贵的成本严重限制了其广泛的商业化应用。本项目致力于开发新型二维过渡金属-氮-碳基复合材料，实现和提高在不同电解质中电催化水裂解制氢和氧的活性，建立材料结构与电催化性能之间的构效关系。在本研究中，首先通过将高度分散的单原子镍锚定在氮-硫共掺杂的二维多孔纳米碳基底，设计开发出一种单原子“镍-氮-硫”碳基水氧化催化剂，通过改变多孔碳纳米片表面的局域电荷分布，降低了速控步骤的活化能，从而提高碱性电催化水裂解析氧反应活性。其次，采用水热自组装耦合高温固相碳化法合成了二维原子级分散镍-氮-碳包覆金属镍颗粒复合材料，金属镍颗粒与镍-氮-碳之间的强化学耦合作用优化了纳米碳材料表面的电荷分布，降低了水解离过程所需的能量壁垒，极大地加速了碱性电解水析氢反应的质子动力学过程，从而导致高效的电催化析氢活性。此外还开发了一种二维铁-氮掺杂的纳米碳纤维负载于电化学剥离石墨烯复合材料，该复合材料展现出优异的酸性电催化水裂解析氧活性，优于商用的贵金属Ir/C催化剂，高度分散的Fe-N4的配位结构是其催化材料的真正反应活性中心。最后，通过对钼掺杂的钨/锌双金属-沸石咪唑骨架进行碳化处理，制备出一种二维钼掺杂碳化钨修饰的氮掺杂碳基复合材料，该复合材料在酸性、中性、碱性电解液下均显示出优异的电催化水裂解析氢活性。本研究为设计和构建高效二维纳米碳基电解水催化剂提供了新的思路和技术支持，具有良好的研究和应用前景。