碱性介质中Fe/N/C催化剂的氧气还原反应催化性能研究

Electrocatalytic Activity of Fe/N/C Catalyst for the Oxygen Reduction Reaction in Alkaline Electrolyte

以氧化石墨烯(GO)为碳载体,K3Fe(CN)6同时作为N源和Fe源,经热处理后构建了新型Fe/N/C结构的氧气还原催化剂.在热处理过程中,氧化石墨烯上的官能团分解脱离形成活性中心,Fe元素和N元素的同时掺杂是通过氧化石墨烯与K3Fe(CN)6之间的相互作用而实现的.通过傅立叶变换红外光谱(FTIR)和X射线光电子能谱(XPS)表征证明了这种非贵金属催化剂中N元素和Fe元素的成功掺杂,在催化剂中N元素主要是以吡啶式氮、吡咯式氮和石墨式氮的形式存在,Fe(II)和Fe(III)则与其中的吡啶式氮配位形成Fe-Nx结构.采用循环伏安法(CV)和旋转圆盘电极(RDE)技术,研究其在碱性介质中对氧气还原反应(ORR)的电催化性能.实验结果显示:Fe/N/C催化剂具有良好的ORR电催化活性,在碱性溶液中的起始电位为-0.15 V,同时有着良好的稳定性和抗甲醇性能.

Fuel cells have been recognized as one of the most promising power sources due to their high efficiency and low emissions.However,the high cost and scarcity of traditional Pt-based catalyst limit their commercialization.More intensive research have been focused on the development of non-noble-metal catalysts in order to replace Pt for catalyzing oxygen reduction reaction（ORR）.Recently,it was reported that the Fe/N/C catalyst have high activity toward ORR.Chemical vapor deposition（CVD） is the most common method for the preparation of the Fe/N/C catalyst.However,the cost of CVD method is much higher.Here we report a facile method for the preparation of Fe/N/C catalyst for ORR in alkaline electrolyte.The catalyst is prepared by using graphene oxide as carbon support,and K3Fe（CN）6 as both nitrogen and iron sources.The precursors are then treated thermally at 800 ℃ under nitrogen atmosphere.In the process of heat treatment,the functional groups of graphene oxide are decomposed to form active center.Simultaneous doping of N and Fe can be realized by the interaction between graphene oxide and K3Fe（CN）6.The non-noble-metal catalyst is further characterized by Fourier transform infrared spectroscopy（FTIR） and X-ray photoelectron spectroscopy（XPS）.It shows that N and Fe elements are successively doped into the graphene substrate.In the catalyst,N elements exist mainly in the forms of pyridine N,pyrrole N and graphite N.Fe（II） and Fe（III） are coordinated with pyridine N to form Fe-Nxstructure.The electrocatalytic activity of catalyst is evaluated by cyclic voltammetry（CV） and rotating disk electrode（RDE） experiments.The Fe/N/C catalyst shows high electrocatalytic activity toward ORR in an alkaline solution with an onset potential of-0.15 V vs.Ag/AgCl reference electrode.CVs of consecutive sweep for 2000 cycles are conducted to study the stability of the catalyst.The Fe/N/C catalyst exhibits excellent stability and methanol-tolerant ability.