am0c08829_si_001.pdf (1.01 MB)
Mass Transfer in a Co/N/C Catalyst Layer for the Anion Exchange Membrane Fuel Cell
journal contribution
posted on 2020-07-09, 19:43 authored by Weikang Zhu, Yabiao Pei, Yang Liu, Junfeng Zhang, Yanzhou Qin, Yan Yin, Michael D. GuiverDeveloping
highly efficient non-noble metal catalysts for the cathode
of fuel cells is an urgent requirement for reducing the cost. Although
the intrinsic activity of non-noble metal materials has been greatly
improved, the fuel cell performance is also determined by the mass
transfer within the catalyst layer (CL), particularly at high current
density. Electrochemical impedance spectroscopy (EIS) combined with
rotating disk electrode (RDE) analysis is a powerful tool to quantitatively
analyze the influence of the structural properties on CL performance.
Here, Co/N/C CLs with gradient pore structures are constructed based
on the controllable synthesis of zeolitic imidazolate framework (ZIF)-derived
catalyst. The influences of the carbon support, active site, and catalyst
loading are comprehensively studied by EIS in different regions (kinetic
and mixed-diffusion). The results indicate that a high micro-/mesopore
ratio is beneficial to increasing the density of active sites while
reducing the mass-transfer efficiency. Inversely, abundant mesopores
promote mass transfer, but they result in low active site density.
By carefully adjusting the pore structure and chemical composition
of the ZIF-derived catalyst, the Co/N/C CL shows a low mass-transfer
resistance (95.5 Ω at 0.75 V vs RHE). This work demonstrates
the importance of mass transfer within the fuel cell CL, beyond seeking
only high activity.