Ni–Mo–O nanorod-derived composite catalysts for efficient alkaline water-to-hydrogen conversion via urea electrolysis

• Published in: Energy & environmental science Vol. 11; no. 7; pp. 1890 - 1897
• Main Authors: Yu, Zi-You, Lang, Chao-Chao, Gao, Min-Rui, Chen, Yu, Fu, Qi-Qi, Duan, Yu, Yu, Shu-Hong
• Format: Journal Article
• Language: English
• Published: Cambridge Royal Society of Chemistry 01.01.2018
• Subjects: Alkaline water; Argon; Catalysis; Catalysts; Electrochemistry; Electrolysis; Electrolytic cells; Energy conservation; Hydrogen; Hydrogen evolution reactions; Hydrogen production; Molybdates; Molybdenum; Nanocomposites; Nanorods; Nickel; Nickel compounds; Noble metals; Oxidation; Platinum; Precursors; Purification; Shielding; Urea; Wastewater; Wastewater purification
• ISSN: 1754-5692; 1754-5706
• DOI: 10.1039/C8EE00521D

Photo/electrochemical splitting of water to hydrogen (H 2 ) fuel is a sustainable way of meeting our energy demands at no environmental cost, but significant challenges remain: for example, the sluggish anodic reaction imposes a considerable overpotential requirement. By contrast, urea electrolysis offers the prospect of energy-saving H 2 production together with urea-rich wastewater purification, whereas the lack of inexpensive and efficient urea oxidation reaction (UOR) catalysts places constraints on the development of this technique. Here we report a porous rod-like NiMoO 4 with high oxidation states of the metal elements enabling highly efficient UOR electrocatalysis, which can be readily produced through annealing solid NiMoO 4 · x H 2 O as a starting precursor in Ar. This precursor gives the derived Ni/NiO/MoO x nanocomposite when switching the shielding gas from Ar to H 2 /Ar, exhibiting platinum-like activity for the hydrogen evolution reaction (HER) in alkaline electrolytes. Assembling an electrolytic cell using our developed UOR and HER catalysts as the anode and cathode can provide a current density of 10 milliamperes per square centimeter at a cell voltage of mere 1.38 volts, as well as remarkable operational stability, representing the best yet reported noble-metal-free urea electrolyser. Our results demonstrate the potential of nickel–molybdenum-based materials as efficient electrode catalysts for urea electrolysers that promises cost-effective and energy-saving H 2 production.