Facile preparation of CoFe-MnO2@titania nanotube array bifunctional electrodes for high-current-density water splitting at industrial temperatures

Abstract

The development of bifunctional electrocatalysts for hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) at high current density under industrial temperatures is crucial for large-scale industrial hydrogen production from water splitting. In this work, M-MnO2@TNTA composite electrodes were prepared by depositing various metal ion-doped manganese oxide nanoparticles on the titania nanotube array (TNTA) by successive ionic layer adsorption reaction (SILAR) method, and their HER and OER electrocatalytic performances were investigated in 1 M KOH. Results show that the CoFe-MnO2@TNTA composite electrode prepared by simultaneous doping of Co3+ and Fe3+ in MnO2 exhibits optimal catalytic performance. Compared with MnO2@TNTA without ion doping, the overpotentials of CoFe-MnO2@TNTA at 10 mA cm−2 (η10) for HER and OER are reduced by 571 and 665 mV. In addition, the electrode performance can be significantly enhanced by increasing the test temperature, and the porous array structure enables CoFe-MnO2@TNTA to exhibit better performance at high current densities. At 50 °C, which is the common industrial electrolytic water temperature, the η10 of CoFe-MnO2@TNTA for HER is almost equal to that of the Pt/C electrode. The η100 of CoFe-MnO2@TNTA for HER is reduced by 35 mV compared with the Pt/C electrode. Moreover, η200 of CoFe-MnO2@TNTA for OER is significantly lowered by 111 and 184 mV compared with IrO2 and RuO2 electrodes. Utilizing CoFe-MnO2@TNTA as both the cathode and anode for overall water splitting, the electrolysis voltage is merely 2.33 V under the current density of 200 mA cm−2, much lower than that of IrO2 (+)||Pt/C (–) (2.68 V). The present work may provide a valuable reference for the development of self-supporting bifunctional electrodes suitable for high-current-density water splitting at industrial temperatures.