An external magnetic field increases the probability of spin polarization of magnetic metal nanoparticles and thus can enhance their oxygen reduction and evolution reaction (ORR/OER) catalytic activity. In this paper, carbon?based bifunctional catalysts of magnetic catalytic nanocages are fabricated by uniformly embedding cobalt nanoparticles into macroporous carbon nanofibers. The direct magnetic enhancement is verified by investigating the electrocatalytic ORR/OER performance under an external magnetic field.Designing stable and efficient electrocatalysts for both oxygen reduction and evolution reactions (ORR/OER) at low?cost is challenging. Here, a carbon?based bifunctional catalyst of magnetic catalytic nanocages that can direct enhance the oxygen catalytic activity by simply applying a moderate (350 mT) magnetic field is reported. The catalysts, with high porosity of 90% and conductivity of 905 S m?1, are created by in situ doping metallic cobalt nanodots (?10?nm) into macroporous carbon nanofibers with a facile electrospinning method. An external magnetic field makes the cobalt magnetized into nanomagnets with high spin polarization, which promote the adsorption of oxygen?intermediates and electron transfer, significantly improving the catalytic efficiency. Impressively, the half wave?potential is increased by 20?mV for ORR, and the overpotential at 10?mA cm?2 is decreased by 15?mV for OER. Compared with the commercial Pt/C+IrO2 catalysts, the magnetic catalyzed Zn?air batteries deliver 2.5?fold of capacities and exhibit much longer durability over 155 h. The findings point out a very promising strategy of using electromagnetic induction to boost oxygen catalytic activity.

» Author: Jianhua Yan, Ying Wang, Yuanyuan Zhang, Shuhui Xia, Jianyong Yu, Bin Ding

» Reference: doi:10.1002/adma.202007525

» Publication Date: 18/12/2020

» More Information

« Go to Technological Watch