Synergism of CoO–Ni(OH)2 nanosheets and MOF-derived CNTs array for methanol electrolysis

Abstract

The hydrogen production efficiency of conventional water splitting is limited by the sluggish oxygen evolution reaction, while coupling the methanol oxidation reaction (MOR) with hydrogen production can simultaneously generate value-added chemicals and hydrogen. Herein, 3D CoO–Ni(OH)₂ nanosheets anchored on the metal organic framework-derived CNT arrays (CNTs@CoO–Ni(OH)₂) for MOR is synthesized by template-assisted growth and electrodeposition strategy. The native Ni³⁺OOH is identified as the MOR active sites, while the synergetic effect between Ni(OH)₂ and CoO can promote the Ni(OH)₂ oxidation to the Ni³⁺OOH species. Therefore, CNTs@CoO–Ni(OH)₂ exhibits a low potential of 1.36 V vs. RHE at 100 mA cm⁻², small Tafel of 43.92 mV dec⁻¹, and high faradaic efficiency (>95%) in MOR, which is comparable or better than the reported high-end electrocatalysts. Furthermore, the Pt||CNTs@CoO–Ni(OH)₂ system only requires a low cell voltage of 1.39 V to reach 10 mA cm⁻², which is approximately 190 mV lower than that of water electrolysis. Therefore, this study provides a rational electrode structural design strategy for the electrochemical upgrade of methanol to formate with energy-saving H₂ production.