The poor conductivity and instability of layered dihydroxides (LDHs) limit their widespread application in oxygen evolution reaction (OER). In this study, the composite electrode of NiMn-LDHs, reduced graphene oxide (rGO) and nickel foam (NF), i.e., NiMn-LDHs/rGO/NF, was prepared by a hydrothermal method. When subjected to oxygen evolution reaction (OER) catalytic performance in a solution of 1 M KOH, the NiMn-LDHs/rGO/NF composite catalyst exhibited an overpotential of only 140 mV at a current density of 10 mA cm−2and a Tafel slope of 49 mV dec−1, which is not only better than the comparing RuO2/NF catalyst, but also better than most of the Mn-based and the Ni–Fe-containing bimetallic OER catalysts reported in the literature. The excellent electrocatalytic performance is ascribed to the efficient integration of ultrathin NiMn-LDH sheets, thin-layered rGO and NF, contributing significantly to the decrease in charge transfer resistance and the increase in electrochemically active surface area. Moreover, NF plays a role of current collector and a role of rigid support for the NiMn-LDHs/rGO composite, contributing extra conductivity and stability to the NiMn-LDHs/rGO/NF composite electrode.
Layered double hydroxides (LDHs) containing transition metals with unsaturated d-bands are ideal candidates for oxygen evolution reaction (OER). However, the bulk layers and congested interlayers block the active sites and avoid the electrolyte access to the internal space. In this work, we report a simple coprecipitation coupled with the hydrothermal method for the direct growth of bimetallic NiCo-LDHs (5.01 nm), NiMn-LDHs (3.45 nm) and trimetallic NiCoMn-LDHs nanosheets (1.26 nm) on Ni foam and these fabricated electrodes exhibit the superior performance for OER. Notably, the NiCoMn-LDHs nanosheets exhibit the lowest overpotential of 290 mV at 20 mA cm −2 and the smallest Tafel slope of 87 mV dec −1 , reducing by 20–40 mV and 31–39 mV dec −1 in comparison with those of bimetallic NiCo-LDHs (310 mV, 118 mV dec −1 ) and NiMn-LDHs (330 mV, 126 mV dec −1 ). This excellent performance is attributed to the 2D structure of the nanosheets and an abundance of exposed active sites, especially oxygen vacancies . Additionally, NiCoMn-LDHs nanosheets exhibit the smallest charge transfer resistance (R ct ) of 6.3 Ω and the largest electrochemical double layer capacitance (C dl ) of 5.52 mF cm −2 than those of the bimetallic NiCo-LDHs (11.0 Ω, 4.85 mF cm −2 ) and NiMn-LDHs (30.6 Ω, 3.00 mF cm −2 ). Furthermore, NiCoMn-LDHs nanosheets maintain good durability over 10 h and cyclic stability without distinct change. This work offers a facile strategy to design various types of bimetallic and trimetallic LDHs boosting for OER process.
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