电催化降解污染物产氢-补能的净水新技术

Hydrogen (H2) has been considered as the ideal energy carrier, which possessed the highest energy density we've ever discovered. Electrocatalytic water splitting, a promising and sustainable H2 production technology, was comprised by the anodic oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) in cathode. The electrochemical production of hydrogen is hampered by the lack of effective replacements for noble-metal-based materials, which are still the best known catalysts to reduce overpotentials of the (HER) and (OER) in water-splitting reaction. In addition, the standard 1.23 v Potential barrier for water splitting can be decreased after the substitution of OER process by directly transferring of electron from other species in anode. The Ni2P material with outstanding electrocatalytic activity will be applied as the bifunctional electrode, whereby an electrochemical water purification cell will be constructed for the high H2 production using organic contaminants as the electron donor. Transition metal phosphides will be prepared using phytic acid as P source, and multiple metal phosphides will be fabricated by substituting of a fraction of Ni with other metals, including Fe, Mn, and Co. Furthermore, the substitution approach will be optimized for accelerating the formation of active sites NiVIOOH, thereby enhancing the degradation efficacies under the relative low bias. Additionally, the transformation mechanism of organic contaminants on the anodes will be deeply investigated using various in-situ characterizations. At the meantime, the as-produced H2 in cathode will be applied as the clean fuel for the electric generation, suppling the energy consumption during the electrochemical water treatment process.

H2被公认为理想能量载体，具有已知燃料中最高的能量密度。基于电化学分解水原理，电解水技术利用电能或太阳能驱动水分解为氢气和氧气，被认为是最有前途和持续性的产氢途径。然而，电解水需要高活性、高稳定性的非贵金属氢析出和氧析出催化剂以使水电解反应经济节能。此外，若以其它物质作电子供体替代阳极析氧，可降低电解水所需1.23 V的热力学标准电势。本项目拟选用具备较强电催化活性N2P为电极材料，组建以污染物为电子供体，协同阴极电催化产氢-补能净水技术。拟选用植酸为磷源，组装和制备多元金属磷化物，通过控制其他过渡金属取代形态及比例，调控电极理化特性，加速电化学阳极表面活性中心（NiVIOOH）生成，实现低能耗下污染物快速矿化燃烧。同时，深化电极表面高价态金属氧化物形成的微观机制，阐明元素掺杂对其形态转化的影响，及其对污染物的转化机制。利用阴极所产的氢气做燃料，构建污染物降解协同催化产氢-补能净水新技术。

通过定向转化水中污染物实现能源回收，是有效解决环境问题和能源危机的一个重要途径。氢气（H2）被公认为理想能量载体，具有已知燃料中最高重量能量密度。电解水产氢是当前获取氢能主要方式，鉴于电催化析氧反应动力学缓慢、能量势垒高等瓶颈问题，我们首先通过微纳重构手段，负载过渡金属磷化物纳米片于泡沫电极表面，并以此构建阳极氧化污染物辅助阴极高效产氢电化学反应过程。对比反应前后高分辨透射电镜结果发现，电化学过程中金属磷化物表面形成非晶层（金属羟基化合物）实为氧化活性物种。X射线光电子能谱（XPS）和原位拉曼光谱（Raman）发现，相较于析氧反应的四电子转移至高价态NiVI过程，污染物存在下，双电子转移至NiII的短程反应过程实加速阳极电荷转移的首要因素。基于此，我们设计并优化了穿透式连续流反应器，目标污染物的氧化降解效率可达79.6％；外加电压仅1.50 V可驱动~30 mA电流密度，电压增至1.70 V，电流密度可高达150 mA。为进一步实现所产氢气的实际利用，我们研发了一种“按序批式”无膜电化学反应器，该反应设备辅以磷化钴（CoP）纳米阵列负载多孔电极为中间调节器，通过CoP电极对电荷高效的储存特性，实现阴极持续充电产氢、阳极快速放电去污的功能，在时间上可有效地分开电解池中的阴极析氢和阳极污染物降解反应。10 mA cm-2的充电电流密度下，可实现1500 s持续产氢，为后续氢气收集提供时间保障；随后，串联中间调节器与Ni基阳极，通过阳极表面快速转化氨氮污染物完成存储能量的迅速消耗。