Superb Bifunctional Water Electrolysis Activities of Carbon Nanotube-Decorated Lanthanum Hydroxide Nanocomposites

Abstract

For highly efficient hydrogen production from electrocatalytic water electrolysis, developing a high-fidelity electrocatalyst is pivotal. Herein, we demonstrated the excellent water-splitting performances of the carbon allotrope-decorated rare earth oxide nanocomposite system, which was composed of lanthanum hydroxide (La(OH)3) and carbon nanotube (CNT). The nanocomposites of CNT-La(OH)3 were fabricated via facile ultrasonication using La(OH)3 nanoparticles and CNT nanofibers, and they exhibited excellent bifunctional water-splitting activities. For the hydrogen evolution reaction, CNT-La(OH)3 showed low values of both overpotential (150 mV) and Tafel slope (113 mV/dec) in 1 M KOH at -10 mA/cm2. Additionally, for the oxygen evolution reaction, CNT-La(OH)3 also displayed small values for their overpotential (310 mV) as well as the Tafel slope (39 mV/dec). Furthermore, both bifunctional hydrogen- and oxygen-evolution reactions were confirmed to be stable in chronopotentiometric tests. From the material characterization and the electrochemical characterization, such excellent bifunctional water electrolysis performances were ascribed to the synergetic effects of hybridization of La(OH)3 (i.e., a large number of electrochemically active sites of 304 cm2) and CNT (i.e., high charge transport conductivity). The results specify that the present CNT-La(OH)3 nanocomposite system possesses ample aptitude as a superior electrocatalyst for next-generation hydrogen production technology.