Multi-Dimensional Ternary Nano-Transition Metal Oxides as Bifunctional Electrocatalysts for Water Electrolysis to Hydrogen Production

Abstract:

Transition metal oxides are considered as potential catalysts for hydrogen production in alkaline water electrolysis due to their low cost， easy fabrication， and excellent electrochemical properties. But the investigation of their morphology on catalyst performance is insufficient. In this paper， multi-dimensional （one-dimensional （1D）， two-dimensional （2D）） gear-shaped transition metal oxide catalysts （NF/NCFO-g） are designed and used as bifunctional electrocatalysts for hydrogen production. In the 1 M KOH solution and a 100 mA cm-2 current density， NF/NCFO-g exhibited anodic overpotential of 0.23 V and a cathodic overpotential of 0.29 V， as well as Tafel slopes of 196 （anodic） and 233 mV dec-1 （cathode）， which are superior to both 1D （NF/NCFO-n） and 2D （NF/NCFO-s） catalysts. The synergistic effect between the “apical advantage” of the 1D nanoneedle and the surface charge effect of the 2D sheet structure are responsible for the excellent electrocatalytic performance of NF/NCFO-g. The “apical advantage” causes a large amount of charge to accumulate at the tip， rendering the inner layer capacitance width being reduced， while the surface charge of 2D sheet structure helps form more oxygen vacancy active sites， resulting in an optimized reaction energy of the transition state. In addition， at high current densities， the 1D nanoneedle structure enhances hydrophilicity and reduces the bubble radius， thus accelerating the bubbles release.

Key words:water electrolysis;alkaline;catalysts;transition metal oxide;morphology