Highly effective oxygen reduction reaction electrocatalysis: Nitrogen-doped hierarchically mesoporous carbon derived from interpenetrated nonporous metal-organic frameworks

Abstract

Nitrogen-doped carbon materials with hierarchically mesoporous structure are synthesized in the present work via the pyrolysis of an interpenetrated non-porous metal-organic framework (MOF), viz. [Zn2(TPT)(BDC)2]·H2O (SCUT-11, TPT=tris(4-pyridyl)triazine, BDC=1,4-benzenedicarboxylate), as the precursor. X-ray diffraction reveals that the synthesized metal-organic framework (MOF) is of high purity of the crystalline phase, and its structure follows our previously reported SCUT-11. This triply-interpenetrated MOF features high density of Zn cations in their interwoven packing structure, which act as effective pore-forming agent to generate mesopores in final carbon. Physicochemical characterizations reveal that the resultant carbon has high specific surface area and bimodal mesopore size distribution, which originate from the removal of metal oxide and/or metal zinc. These textual features favour both oxygen mass transfer and accessibility of catalytically active sites. Electrochemical results confirm that the resultant carbon, synthesized by pyrolysis at 900°C, shows a superior oxygen reduction reaction (ORR) activity, which is associated with high onset and half-wave potential up to 1.0 and 0.88V, respectively. Further investigation suggests that the as-synthesized carbon catalyst exhibits a remarkable insensitivity towards anions, like sulphate and phosphate, compared with the Pt counterpart. The above features make this carbon catalyst promising to be widely used in different fuel cell types.