Trimetallic NiCoFe-Layered Double Hydroxides Nanosheets Efficient for Oxygen Evolution and Highly Selective Oxidation of Biomass-Derived 5-Hydroxymethylfurfural

Selective conversion of renewable sources is necessary for developing energy generation technology and protecting the environment. Herein, this work reports a one-step controllable synthesis of trimetallic NiCoFe-layered double hydroxides (NiCoFe-LDHs) nanosheets (1.36 nm) for both an efficient oxygen evolution reaction (OER) and highly selective oxidation of biomass-derived 5-hydroxymethylfurfural (HMFOR) into value-added 2,5-furandicarboxylic acid (FDCA). For comparison, two sets of bimetallic NiCo- and NiFe-LDHs were similarly synthesized and evaluated. In the OER process, the optimal NiCoFe-LDHs nanosheets exhibited the lowest necessary overpotential (288 mV) to reach 10 mA cm (-2) and the smallest Tafel slope of 92 mV dec(-1) compared with NiCo-LDHs (347 mV, 115 mV dec(-1)) and NiFe-LDHs (303 mV, 108 mV dec(-1)). The performance was also superior to most previously reported LDHs catalysts. Additionally, NiCoFe-LDHs nanosheets exhibited a much smaller charge transfer resistance (Rct) of 1.0 Omega and a larger C-dl value of 2.62 mF cm(-2) compared with NiCo-LDHs (2.1 Omega, 1.94 mF cm(-2)) and NiFe-LDHs (1.4 Omega, 2.22 mF cm(-2)), indicating fast catalytic kinetics. Furthermore, the NiCoFe-LDHs nanosheets possessed excellent durability over 10 h, much better than that of NiCo- and NiFe-LDHs. NiCoFe-LDHs catalysts also exhibited high performance in the oxidation of 5-hydroxymethylfurfural (HMF) to FDCA, which is a key precursor for the sustainable synthesis of polymers (e.g., polyethylene 2,5-furandicarboxylate (PEF)). An ultralow overpotential of 280 mV was required to achieve 20 mA cm(-2), nearly 120 mV less than the activity in pure 1.0 M NaOH. The reaction intermediates and products were qualified by liquid chromatography-mass spectroscopy system (LC-MS) and LC, where 95.5% conversion of HMF and 84.9% yield of FDCA were obtained in 1 h. The reaction kinetics and possible pathways were further investigated. As a unique report utilizing trimetallic LDHs catalysts for OER and HMFOR, this study provides a promising perspective for energy conversion and electrocatalytic processing of biomass-derived monomers.