Multiwalled carbon nanotubes twined α-nickel hydroxide microspheres as high-efficient urea electrooxidation catalysts

Abstract

Multiwalled carbon nanotube (MWCNT) twined α-Ni(OH)2 microspheres, denoted as α-Ni(OH)2@MWCNT, are synthesized by a facile solvothermal method and are developed as a remarkably active catalyst for urea electrooxidation in alkaline media. Through optimizing the mass ratio between α-Ni(OH)2 and MWCNT, it is found that α-Ni(OH)2@MWCNT catalyst with a weight ratio of 2.5:1 affords the highest current density of 2503 mA cm−2 mg−1 at the potential of 0.58 V versus Hg/HgO and the largest exchange current density of 1.49 × 10−4 mA cm−2 among all the studied catalysts, which are much higher than that of pure α-Ni(OH)2 microspheres and are about one order of magnitude higher than that of reported Ni(OH)2 nanosheets. Additionally, the α-Ni(OH)2@MWCNT catalysts also present superior durability than pure α-Ni(OH)2. The exceptional catalytic performance of α-Ni(OH)2@MWCNT catalysts is attributed to the good electronic transport of MWCNT and favorable mass transport facilitated by α-Ni(OH)2 hollow porous microspheres. These results suggest the feasibility of an easy and low-cost solvothermal method to develop high-efficient catalyst for urea electrooxidation. Bird-nest-like microspheres of α-Ni(OH)2@MWCNT catalyst were synthesized with MWCNT twined α-Ni(OH)2 ultrathin nanosheets by an economical solvothermal method.