镍基中空纤维催化剂实现甲烷高效电催化转化

随着天然气以及页岩气为代表的非常规天然气的大规模开采,甲烷作为化工原料的直接转化利用受到了越来越多的关注.然而,甲烷分子具有极其稳定的正四面体结构,其物理化学性质非常稳定,如具有高达439 kJ/mol的C-H键能、极弱的电子亲和力、相当大的离子化能量和低的极化率,这都使得甲烷分子C-H键的活化相当困难.如何实现甲烷直接高效催化转化被誉为催化领域的'皇冠式'课题.与经甲烷重整制合成气,然后通过F-T合成获取化学品的间接转化法相比,甲烷直接转化无论在物料、能量转换效率还是在设备成本、环境保护等方面都有着非常明显的优势.以甲烷氧化偶联以及非氧化偶联(如无氧芳构化等)为典型代表的甲烷直接转化研究不断取得突破,但其各自都存在一定的局限性.相比于热催化转化路径,电催化转化路径在许多方面存在着十分明显的优势:(1)反应条件温和,甚至在常温常压条件下也能实现甲烷电催化转化反应的发生;(2)可调控程度高,仅需调节关键实验参数如电压和电流等,就能实现对反应过程热力学以及动力学的调控;(3)能够利用可再生电能驱动甲烷转化反应的发生,可将低品阶的电能转化并存储为化学能.本文采用Ni中空纤维作为基底,在其表面构筑NiO活性层,将NiO@Ni中空纤维作为电极,实现了常温常压条件下的甲烷电催化转化.通过X射线衍射、扫描电镜、透射电镜等表征手段,确定了中空纤维特有的多孔三维结构、气体传输规律、NiO活性层分布状态等物化性质.通过电化学交流阻抗与循环伏安等测试手段,获得了电荷传递、电化学活性比表面积等电化学性质.恒电压电氧化甲烷研究发现,1%NiO@Ni中空纤维具有最优的催化活性,分别在1.44 V与1.46 V(vs.RHE)电势下获得54%的甲醇法拉第效率和85%的乙醇法拉第效率.

Efficient methane electrocatalytic conversion over a Ni-based hollow fiber electrode

Natural gas and shale gas,with methane as the main component,are important and clean fossil energy resources.Direct catalytic conversion of methane to valuable chemicals is considered a crown jewel topic in catalysis.Substantial studies on processes including methane reforming,oxidative coupling of methane,non-oxidative coupling of methane,etc.have been conducted for many years.However,owing to the intrinsic chemical inertness of CH4,harsh reaction conditions involving either extremely high temperatures or highly oxidative reactants are required to activate the C–H bonds of CH4 in such thermocatalytic processes,which may cause the target products,such as ethylene or methanol,to be further converted into coke or CO and CO2.It is desirable to adopt a new strategy for direct CH4 conversion under mild conditions.Herein,we report that efficient electrocatalytic oxidation of methane to alcohols at ambient temperature and pressure can be achieved using a NiO/Ni hollow fiber electrode.This work opens a new avenue for direct catalytic conversion of CH4.