Highly active layered double hydroxide-derived cobalt nano-catalysts for p-nitrophenol reduction

Abstract

and Akron Avenue, Lubbock, TX 79409. AbstractReplacing precious noble-metal catalysts with non-precious metal ones is a well-recognized strategy for reducing the cost of catalytic water treatment. The implementation of this strategy is, however, challenging. To reduce the cost by using non-precious metal catalysts, the reactivity ratio between non-precious and precious metal catalysts must exceed their price ratio. Here, we report for the first timethat the parity condition has been surpassedfor cobalt (Co), in comparison to the most active precious metal catalyst made of palladium,in the catalytic reduction of pnitrophenol with borohydride. This is achieved by affixing Co nanoparticles on two-dimensional layered double oxide (LDO) nanodisks through thermal phase transformation of cobaltmagnesium-aluminum layered double hydroxide precursors. We show that the catalytic activity of LDO-Co is a function of Co molar fraction among metal cations.The highest reactivity is achieved at a molar fraction of 28%, giving a pseudo first order rate constant of 86(±3) min -1 at 25 o C for a catalyst dose of 1 g L -1 (as Co) and an initial p-nitrophenol concentration of 0.2 mM.Compared to other Co nano-catalysts described in the literature, the LDO-Co design has improved the reactivity of cobalt by at least 49 times. We further show that the high reactivity of LDO-Co remains after repeated reuse as well as after borohydride is replaced by formate, a moderate reductant and hydrogen donor. We propose that the high reactivity and superior longevity of LDO-Co are results of the heteroepitaxial fixation of cobalt on LDO through cobaltoxygen bonds that are similar to those in spinel cobalt oxide.

CuPd Bimetallic Nanoparticles Supported on Magnesium Oxide as an Active and Stable Catalyst for the Reduction of 4-Nitrophenol to 4-Aminophenol

“…This period of time for the reaction to start has been previously observed in several catalytic systems applied in this reaction, for example, for Co [33], Cu [8] or Au [34] catalysts. The causes of this induction period have been deeply studied for Au faceted metal particles [3] and the authors stated that any limitation by diffusion can be discarded.…”

Preparation of Metal-Free Nitrogen-Doped Carbon Material and Its Catalytic Performance

“…Some of catalysts for the reduction of p-nitrophenol are loaded with precious metals as active components, such as: gold [15] and silver [16]. Non-precious metals can also be loaded in the material as active components, such as: cobalt/hydrotalcite [17] and copper/perlite [18].…”

Preparation of Nitrogen-Doped Carbon Material from Monosodium Glutamate and Its Catalytic Performance

“…Therefore, the catalytic reduction of 4-NP to 4-AP with NaBH4 has been widely studied. Most of the existing researches on the reaction are based on metallic catalysts, such as: Ag [14], Au [15], Cu [16], Co [17], and Bi [18], which are restricted due to limited reserves, high cost and low stability.…”