Paper EH-TuP7
Bimetallic Cobalt-Iron Hydroxide Encapsulated in Organic Ligand Derived Carbon Layers as an Efficient Electrocatalyst for Oxygen Evolution Reaction

Tuesday, December 4, 2018, 4:00 pm, Room Naupaka Salon 1-3

Water electrolysis as one of the prospective approach to produce hydrogen is limited by the anodic oxygen evolution reaction (OER) due to its sluggish kinetics. Considering the practical application, the development of highly efficient non-noble OER catalysts is essential. Among the reported low-cost electrocatalysts, CoFe-based oxides or hydroxides are intriguing owing to the rich redox chemistry. However, the severe aggregation and intrinsically poor electronic conductivity hinder their electrocatalytic performance. Hybridizing cobalt-iron oxides or hydroxides with carbon materials can not only enhance the conductivity of the catalyst, but also facilitate the uniform distribution of metal species within carbon matrix, thus improving the electrochemical performance towards OER. In view of this, we report here the bimetallic cobalt-iron hydroxide encapsulated in carbon layers derivedfrom organic ligand (Schiff base) via hydrothermal carbonization. In alkaline media, Co Fe/C loaded on GC electrode delivers a current density of 10 mA cm^-2 at an overpotential of 260 mV and exhibits a low Tafel slope of 45.2 mV dec^-1 as well as excellent durability. The remarkable OER performance outperforms those of CoFe-based electrocatalyst in the literature.

Keywords: Oxygen evolution reaction, cobalt-iron hydroxide, organic ligand, electrocatalyst

Results

As shown in Figure 1, the Co_1.2Fe/C delivers a current density of 10 mA cm^-2 at an overpotential of 260 mV and exhibits a low Tafel slope of 45.2 mV dec^-1 as well as excellent durability in 1M KOH solution.

Figure 1 (a) LSV curves of GC, Co_1.2Fe and Co_1.2Fe/C; (b) Tafel plots of Co_1.2Fe and Co_1.2Fe/C; © Chronopotentiometric measurement of Co_1.2Fe/C at 10 mA cm^-2. All tests were carried out in 1 M KOH.

Conclusions

The Co_1.2Fe/C exhibits excellent OER performance in alkaline media, which can be ascribed to the following factors: 1) the homogenous distribution of metal hydroxide within carbon matrix inhibits the aggregation of the active nanoparticles; 2) the excellent electronic conductivity enables fast electron transport during the OER process; 3) the synergetic effect between the Co_1.2Fe hydroxide and carbon species also contributes to the improvement of the electrochemical performance.

Reference

[1] S. Yin, W. Tu, Y. Sheng, Y. Du, M. Kraft, A. Borgna, R. Xu, Adv. Mater. 2017, 1705106.

[2] F. Li, J. Du, X. Li, J. Shen, Y. Wang, Y, Zhu, L. Sun, Adv. Energy Mater. 2018, 1702598.