基于单原子催化提高光电催化还原硝酸盐反应氮气选择性的机理研究

The grand challenge facing in the photoelectrocatalytic reduction of NO3- is the poor selectivity towards N2 production (N2 selectivity). Herein, based on the typical catalysis principles, we propose a solution to solve this issue by constructing single-atomic catalyst (SAC). Firstly, controllable synthetic methods are designed to prepare single Pd atom-loaded porous Cu photocathode materials using atomic layer deposition, hydrothermal or photo-/electro/chemical deposition methods. Then an extension photocathode material, Pd/Cu bimetal SAC-alloy, will be fabricated. The as-prepared cathodes will be assembled in a photoelectrochemical reactor with the Ag/Au modified TiO2 (or ZnO) nanoarrays as photoanodes. The N2 selectivity will be thoroughly investigated. The thermodynamical favorability of N2 selectivity of the SAC reduction of NO3- will be investigated using in-situ FTIR and X-ray adsorption techniques. The kinetics of the SAC reduction of NO3- will be measured using temperature programmed desorption method to explore the affinity of NO3-, NOx and NHx on the surface of SAC. Together with the density functional theory computational analysis, the mechanism of SAC-enhanced N2 selectivity of photoelectrocatalytic NO3- reduction will be proposed. In addition, the SAC system is of more advantageous atom utilization efficiency, stability and cost over nanocatalysts. The study will possibly open a door to developing a practical approach to solve the N2 selectivity of photoelectrocatalytic NO3- reduction.

光电催化还原NO3-反应过程的N2选择性差是亟待解决的科学问题。本项目基于经典催化反应理论，提出通过构建单原子催化材料提高NO3-还原反应的N2选择性。首先采用原子层沉积、水热、光电化学沉积等方法，可控合成单原子Pd负载的多孔Cu电极材料，并进一步拓展至双原子Pd/Cu合金负载的多孔TiO2电极材料，然后分别与Ag/Au修饰TiO2（或ZnO）纳米阵列电极材料组成光电化学反应器，探索控制光电反应过程中N2选择性的影响因素。采用原位红外、X射线吸收技术探讨单原子催化剂活化NO3-的热力学过程；采用程序升温吸脱附法研究单原子催化剂对反应物、中间产物及彻底还原产物NH4+的吸附动力学过程；结合密度泛函理论模拟，揭示单原子催化材料提高N2选择性的作用机理。由于单原子催化材料还具有高催化活性、优异稳定性及低成本的特点，本研究将为开发具有一定应用前景的光电催化还原NO3-技术提供理论依据。

随着农药化肥的大量使用，地表及地下水中的硝酸盐浓度不断升高，所造成的生态危害得到越来越高的关注。本项目主要研究目标是开发具有高效催化还原硝态氮，且具有高氮气选择性的光电催化材料，用以去除水体中的过量硝态氮。本项目基于界面调控技术，构建了具有单-双-多点缺陷态结构的催化材料，形成了催化材料及表面缺陷态的可控合成方法。以缺陷态催化材料为基础，本项目基于光电沉积等方法，在催化表面负载金属及金属合金纳米催化材料，系统探究了催化材料光电催化脱氮的热力学及动力学过程，揭示了脱氮反应机理，并开发了具有较高能量利用效率的电催化反应器。本项目同时开展了拓展型研究，探究了缺陷态催化材料高效协同吸附-催化降解水体中的新污染物，以及光电催化产氢性能及机理。基于上述成果，项目负责人团队共发表高水平论文14篇，授权发明专利2项，申请发明专利5项。相关研究深化了界面催化水处理技术的理论体系，对于高效催化降解含氮类污染物提供重要的理论依据和技术支撑。