2D CoFe-LDH Nanosheet-Incorporated 1D Microfibers as a High-Performance OER Electrocatalyst in Neutral and Alkaline Media
Sreenivasan Nagappan, Arun Karmakar, Ragunath Madhu, Selvasundarasekar Sam Sankar, Sangeetha Kumaravel, Krishnendu Bera, Hariharan N. Dhandapani, Debashish Sarkar, S. M. Yusuf, Subrata Kundu
Abstract
Compositional-variation-induced CoFe-LDHs (with various Co:Fe ratio; LDH, layered double hydroxide) have been prepared via a simple wet-chemical method followed by the formation of 1D microfibers through electrospinning (ES) techniques. The as-synthesized 1D fiber with a Co/Fe ratio corresponding to a 0.5:1 microfiber (CoFe-LDH0.5 fiber) showed the highest oxygen evolution reaction (OER) activity by demanding an overpotential value of 267 mV while the corresponding powder material demands an overpotential value of 312 mV at pH = 14. In addition, the neutral OER activity of the catalysts was also verified in 0.2 M phosphate buffer solution (PBS), and the same CoFe-LDH0.5 fiber demands a lower overpotential value of 300 mV while the CoFe-LDH1 fiber and CoFe-LDH1.5 fiber demand 320 and 340 mV overpotential, respectively. Hence, we have obtained the interesting result that the incorporated 1D fibrous material with lower cobalt content showed a higher activity than the other fibrous materials. A magnetic study shows that the presence of cobalt ions with a lower concentration ensures the higher ferromagnetic (FM) interaction among the cobalt ions which in turn polarize the overall electronic spin of the hydroxide entity. The polarization of the electronic spin results in lowering the energy barrier by omitting the spin inversion barrier.