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In Situ Crystallization of Active NiOOH/CoOOH Heterostructures with Hydroxide Ion Adsorption Sites on Velutipes-like CoSe/NiSe Nanorods as Catalysts for Oxygen Evolution and Cocatalysts for Methanol Oxidation

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journal contribution
posted on 19.12.2019, 18:45 by Jiannan Du, Shijie You, Xuerui Li, Bo Tang, Baojiang Jiang, Yang Yu, Zhuang Cai, Nanqi Ren, Jinlong Zou
Hydroxide ion (OH) adsorption process is critical for accelerating the half-reactions of both metal–air batteries and direct methanol fuel cells in alkaline media. This study designs a rational catalyst/cocatalyst by constructing the readily available OHadsorption sites to boost oxygen evolution reaction (OER) and methanol oxidation reaction (MOR). Cobalt selenide-coated nickel selenide nanorods are in situ grown on nickel foam to obtain CoSe/NiSe-nrs/NF via a one-pot solvothermal synthesis route. CoSe-0.2/NiSe-nrs/NF (Co/Ni molar ratio of 0.26) exhibits an excellent OER activity­(an overpotential of 310 mV at 100 mA cm–2 and a Tafel slope of 58.3 mV dec–1). The differently oriented CoSe/NiSe-nrs with a velutipes-like structure and metallic property provide a promising electrical conductivity for charge transfer. In situ X-ray diffraction tests verify the crystallization of active β-NiOOH during OER, and the crystallized NiOOH/CoOOH contributes to the excellent OER cycling stability in alkaline media. Synergistic effects between CoSe and NiSe-nrs/NF can balance the formation of NiOOH/CoOOH heterostructures to govern the exposure of available active sites. NiOOH/CoOOH as a highly active component can energetically adsorb OH to promote OER. CoSe/NiSe-nrs/NFs as a low Pt-loading (0.5 wt%) support offer the mutually beneficial interactions for promoting cocatalytic and COads (poisonous intermediate) co-oxidation activities toward MOR. The electrochemically active surface area and mass activity of Pt/CoSe-0.2/NiSe-nrs/NF are 85 m2 gpt–1 and 1437.1 mA mgpt–1, respectively, which are much higher than those of commercial Pt/C (10.0 wt%). OH absorbed on the NiOOH/CoOOH structure eliminates COads on the Pt surface via bifunctional mechanisms to improve the MOR activity. This study provides a promising reference for designing the versatile catalysts for energy conversion.