Nickel-Doped ZnO Nanowalls with Enhanced Electron Transport Ability for Electrochemical Water Splitting

This article reports on the growth of 3 mol% nickel (Ni)-doped zinc oxide nanowalls (ZnO NWLs) using the hydrothermal method. Morphological investigation as well as electrical conductivity of the undoped and Ni-doped ZnO NWLs was also discussed. The surface roughness of the formed ZnO NWLs was reduced after Ni-doping. The pore size of Ni-doped ZnO NWLs can be controlled by changing the concentration of hexamethylenetetramine (HMT). As the HMT concentration increased, the pores became larger with increasing surface roughness. The electrical conductivity of the electron-only device based on the Ni-doped ZnO NWLs was higher than that of the undoped one, and it was decreased with increasing the HMT concentration. Our results reveal that Ni-doping and adjustment of the HMT concentration are two key approaches to tune the morphology and electrical properties of ZnO NWLs. Finally, the undoped and Ni-doped ZnO NWLs were used as the catalyst for electrochemical water splitting. The Ni-doped ZnO NWLs with the HMT concentration of 1 mM showed the highest electrochemical performance, which can be attributed to the increased surface area and electrical conductivity.