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

Abstract

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 OH − adsorption 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 CO ads (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 m 2 g pt −1 and 1437.1 mA mg pt −1 , respectively, which are much higher than those of commercial Pt/C (10.0 wt%). OH − absorbed on the NiOOH/CoOOH structure eliminates CO ads 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.

Iron Coordination Polymer, Fe(oxalate)(H2O)2 Nanorods Grown on Nickel Foam via One-Step Electrodeposition as an Efficient Electrocatalyst for Oxygen Evolution Reaction

“…Transition-metal compounds are commonly used as OER catalysts due to their abundance, low cost, and nontoxicity. , Especially, iron, cobalt, and nickel oxyhydroxides (MOOH, M = Fe, Co, Ni) have attracted great attention in recent years. − For example, Feng et al synthesized FeOOH/CeO 2 nanotube electrocatalyst, which exhibited a high OER current density of 80.2 mA cm –2 at 300 mV in 1 M NaOH . Wang et al fabricated hierarchical ultrathin sheet-based CoOOH hollow nanospheres with rich oxygen vacancies, which displayed outstanding OER performance with a current density of 10 mA cm –2 at 275 mV in 1 M KOH .…”

In situ evolution of surface Co2CrO4 to CoOOH/CrOOH by electrochemical method: Toward boosting electrocatalytic water oxidation

“…During 0-1.5 h, the OER reactivity was positively related to the time of the electrochemical anode reaction. Thereafter, the activity decreased slightly, which may be due to the accumulation of CoOOH/CrOOH, which increases the charge-transfer resistance [30]; however, the catalytic performance was still superior to that of Co2CrO4/NF (Fig. S5).…”

Robust copper nanocrystal/nitrogen-doped carbon monoliths as carbon monoxide-resistant electrodes for methanol oxidation reaction

“…Thus, it is crucial to seek highly active, stable and low-cost electrocatalysts for MOR. In recent years, non-noble metal based electrocatalysts, including Co [8,9], Ni [10,11], Cu [12,13], have attracted much attention as active catalysts for MOR. Among these transition metals, copper is a promising ingredient for MOR electrocatalysts, because of its high activity, high abundance, good stability and low price [14].…”