三维自支撑多级结构NiCo LDH/C 电极的构建及催化降解酚类污染物机制研究

Electrocatalytic degradation of phenolic pollutants is an important means to control environmental wastewater. At present, traditional BDD and DAS electrodes are costly and they have weak adsorption capacity for reactants. The limit of mass transfer of pollutants during the reaction process leads to the lower free radical utilization, resulting in lower current efficiency and higher energy consumption. In this project, the porous carbon felt was used as the electrode matrix, and the hollow structure NiCo LDH nanoarrays were grown by in-situ template method, which constructed three-dimensional multilevel NiCo LDH/C electrodes. The adsorption-electrocatalytic oxidation methods were effectively integrated and coupled. The selectivity of the catalytic reaction was improved and the phenols were degraded efficiently. The multilevel structure gave the electrode high specific surface area and developed pore structure, which exposed more active sites and enhanced the catalytic activity. At the same time, it combined the carbon electrode's strong adsorption capacity for phenols, which reduced the mass transfer limit, therefore, the mineralization ratio of phenols and current efficiency were increased and the energy consumption was decreased. The regulation of phenol adsorption and mineralization ratio on micro-structures such as specific surface area, pore structure and LDH morphology of three-dimensional electrodes were discussed, the synergistic mechanism of adsorption-electrocatalysis was established, the reaction mechanism and kinetic model of phenol degradation were clarified; the relationship between microstructure and catalytic performance ware revealed. The implementation of this project will provide theoretical and experimental basis for the removal of refractory organic matter, which contributes to the development of high-performance practical electrode materials.

电催化降解酚类污染物是治理环境污水的重要手段，目前传统BDD和DAS电极成本较高且对反应物吸附能力较弱，反应物的传质限制导致自由基利用率较低，因而电流效率低、能耗高。本项目拟以多孔碳毡为电极基体，采用原位模板法生长中空结构NiCo LDH纳米阵列，构建三维多级结构NiCo LDH/C电极，将吸附法-电催化氧化法进行有效集成与耦合，提高催化反应选择性，实现酚类高效降解。多级结构赋予电极高比表面积和发达孔结构，暴露更多活性位点，提高催化活性；同时结合碳电极对酚类较强的吸附能力，减少传质限制，进而提高酚类的矿化率和电流效率、降低能耗。探索三维电极的比表面积、孔结构、LDH形貌等微结构对酚类吸附及矿化率的调控规律，建立吸附-电催化协同作用机制，阐明酚类降解的反应机制及动力学模型；揭示电极微观结构与催化性能之间的联系。本项目的实施为难降解有机物去除提供理论和实验基础，有助于高性能实用电极材料的开发。

电催化反应在能源、水处理等领域中占据重要地位。目前，昂贵的价格和有限的储量严重限制了贵金属电催化剂的大规模使用，因此探索高效和稳定的非贵金属电催化剂具有重要意义。然而，大部分电催化剂往往只能催化单一反应，不能满足废水中污染物降解、析氧/析氢反应(OER/HER)等多功能电催化的需求。因此，合理设计多功能电催化剂尤为重要。本项目以导电材料为基底，通过MOF牺牲模板法原位生长过渡金属氢氧化物构建的三维多级自支撑电极具有较大比表面积、更多活性位点，因而具有优异的催化性能，其对酚类污染物降解具有较好的电催化氧化性能，研究微结构改变对酚类降解性能的影响。更为显著的是此电极（或杂原子改性电极）在电催化水分解产氢/氧方面具有电流密度大、过电位较低的优势。研究电极异质界面结构调控对于有机物降解和析氢/氧的影响规律，分析反应过程机制及动力学影响因素；深入研究异质界面中杂原子掺杂对催化材料电子结构以及催化剂本征活性的改变和影响，进一步提高电极催化性能，为三维自支撑实用电极的开发提供有效策略。. 本项目结合碳毡、MOFs和NiCo LDH的优点，设计了三维空心纳米笼结构的镍钴氢氧化物电极。三维空心纳米笼结构可以有效地解决电化学循环下的结构坍塌问题，从而有效提高电极在催化过程中的稳定性。所制备的三维自支撑多功能电极对苯酚、对硝基苯酚降解具有一定作用，同时在碱性海水中对HER和OER具有优异的稳定性和大电流的优势，将其同时作为阴阳两极应用于整体海水裂解时，所需裂解电压极低，其性能优于大多数碳基过渡金属电极。此外，本项目还进行拓展性研究，鉴于金属化合物催化剂的性能可进一步提高，通过引入杂原子调控金属电子构型来构建异质界面成为一种提高催化剂性能的有效途径。基于异质界面处丰富的活性位点和不同组分之间的协同作用，通过改变组分和形貌调控设计了两种杂原子(硫/磷)修饰的多功能自支撑电极材料：NiCo LDH/NiCoS和P-doped CoMoO4-CuOx/CF，均实现高效的多功能电催化过程。