准原子分散铂族金属催化和H*/H2O2介导的污染物间接电化学去除研究

The electrocatalytic processes has great potential in the field of environmental decontamination. However, the practical application of this process in environmental management is hindered by materials science and economy challenges, as current electrocatalyst suffer from high cost but low stability, and the energy utilization efficiency is very low. In this proposal, we focus on elucidating the relationship between the structure of the reactive center and their activity in the two key process that involved in the electrochemical removal of pollutants---- the in the formation/stabilization of atomic H/H2O2, as well in the removal of the pollutants, and propose that the designing of ultrathin transition metal oxide nanosheets supported (Quasi) atomic dispersed Platinum group metal nanocatalyst to partially overcome the above mentioned drawbacks of the existing materials. We believe that in this catalyst, make full use of the atomic H that produced from the Volmer process on transition metal oxides, platinum group metal atoms multiple-function as stabilize center for atomic H, active center for generation of H2O2 through the two electrons pathway, and finally as the reaction site for the removal of environmental pollutants by atomic H/H2O2. Through suppressing the consumption of atomic H and energy by the hydrogen evolution reaction, and change the contaminant removal pathway from direct electrochemical reduction to atomic H/H2O2-mediated indirect route, it is anticipated that we can achieve low energy consumption and highly efficiency removal of environmental pollutants. Meanwhile, considering the critical role of single-atom catalyst in verious chemical processes, and the importance of suppressing the HER during the energy conversion/storage process, the implementation of this project not only has environmental significance, but also meaningful to the relevant fields.

电催化过程在污染物去除领域具有重要应用前景。当前电催化体系存在无法平衡H*/H2O2等活性物种的生成/稳定与HER过程的抑制，污染物去除途径主要为直接电还原、过电位高、能量利用效率低等问题。本项目拟从阐明铂族金属活性中心的构象与H*/H2O2的生成/稳定，以及间接还原/氧化去除污染物两个关键过程的构效关系入手。综合利用金属氧化物超薄纳米片在提高铂族金属原子利用率、稳定性和调控其构象/电子结构方面的独特优势，并结合其自身优良电催化活性，构建金属氧化物超薄纳米片负载的（准）原子分散铂族金属催化剂。在强化H*/H2O2介导的间接还原/氧化物去污途径的基础上，实现环境污染物的高效、低能耗电催化去除甚至矿化。鉴于单原子催化剂在多种化工过程中的关键作用，HER过程的抑制和电催化过程在能源转化/储存过程的重要角色，本项目的实施不仅具环境化学意义，获得的成果在上述领域也具有参考价值。

卤代有机污染物具有高毒性，难生物降解，且在我国环境介质中广泛检出。基于催化/电催化的还原脱卤过程是应卤代有机污染的有效手段，阐明还原脱卤反应界面过程对于设计活性高、成本低、稳定性的催化体系具有重要意义。. 研究通过系统控制Pd还原脱卤电催化剂的粒径和表面缺陷比例，发现在电催化还原脱卤过程中，Pd的缺陷位点可以高效生成/稳定活性H*, 是决定还原脱卤效率的关键位点。而在Pd 纳米颗粒表面，活性H*的产率、还原产物苯酚脱附和卤代酚吸附在不同电势区间起不同的作用，但整体法拉第效率皆小于10%，远低于富缺陷的Pd 纳米线的接近40%。基于这一认识，研究发展了Pd1/TiO2-x 电催化剂，通过完全抑制活性H转化为H2或者晶格吸附H, 将法拉第效率提高到了60%。更重要的是，得益于Pd与缺陷型TiO2-x间的协同作用，该催化剂的质量活性达到了Pd 纳米线和普通Pd/C的200倍和1000左右，显著提高了电化学脱卤过程的环境实用性。. 于此同时，高浓度的环境污染物经过转化，尤其是无害化处理，对其中的具有资源化的产物进行回收，不仅可以降低排放，还可以有效的提高整个水处理过程的经济性。基于这一认识，系统的研究了在高浓度卤代酚处理过程中直接将其转化为高附加值化学品环己酮的可行性。研究通过引入Au, Pd设计了Au@PdRh三金属催化剂，有效的缓解在催化加氢过程中活性H在Rh表面的强吸附中毒，实现了室温常压下卤代酚的高效转化为环己酮。除苯酚外，卤素阴离子，如Br-等也是有价资源。基于金属前驱体（PdCl42-，AuCl4-）与FeCl3间的配体置换过程，发展了一步法合成负载型M3Fe/γ-Fe2O3 NSs的新方法，并利用Au3Fe对Pd进行二重负载设计了Au3Fe@Pd/γ-Fe2O3 NSs。该催化剂可以高效转化溴代阻燃剂生产废水中的有机溴（3000 mg L-1）为无机溴，便于资源回收。. 项目完成了研究任务，达到了预期目标。培养优青2人，中科院青促会优秀会员1人。在Environ. Sci. Technol., CCS Chem, ACS Nano, Adv. Funct. Mater.等高影响力期刊发表研究论文7篇。