In situ transformation of Co-MOF nanorods into Co3S4/Ni3S2 nanotube arrays for electrochemical biomass upgrading

Abstract

Electrocatalytic oxidation has emerged as an efficient method for upgrading biomass to value-added products. Herein, hollow Co₃S₄/Ni₃S₂ nanotube arrays were synthesized in one pot on nickel foam (NF) under solvothermal conditions (120 °C, ethanol, 3 h), using thioacetamide (TAA) additive and Co metal–organic framework (Co-MOF) nanorod arrays as the template. The in situ transformation of nanorods into nanotubes occurred via ion exchange and synchronous etching processes in which Co-MOF nanorods provided Co²⁺, NF provided Ni²⁺ and TAA provided S²⁻ that enabled the reassembly of constituents into Co₃S₄/Ni₃S₂ nanotube arrays. The nanotube arrays applied as electrodes for electrocatalytic oxidation of 5-hydroxymethylfurfural (HMF) exhibited a wide potential application range from 1.35 to 1.7 V vs. RHE and afforded nearly 100% 2,5-furandicarboxylic acid yields and faradaic efficiencies (FE). The as-prepared Co₃S₄/Ni₃S₂ electrodes were applied to furfural, furfuryl alcohol and benzyl alcohol to form the corresponding acid products at yields and FE of up to 99.2% and 98.3%, respectively. The hollow structure of Co₃S₄/Ni₃S₂ nanotube arrays improves electron transport, expands the specific surface area, and increases substrate access to active catalytic sites, and the simple fabrication method greatly expands the scope for preparing non-noble metal-based nanotube arrays for electrocatalytic applications.