Magnetically-actuated mesoporous nanowires for enhanced heterogeneous catalysis

- Magnetic actuation of purely magnetic mesoporous nanowires (NWs) is revealed as a novel and efficient catalysis procedure in reactions of heterogeneous catalysis in environmental and energy fields.
- Mesoporous Co-Pt NWs are simultaneously effective catalysts itself and the stirring device, using magnetic fields, to catalyse reactions in solution.
- The procedure allows ultra-fast degradation of different types of pollutants.
- The NWs show very high effectivity for hydrogen generation (25.0 L H2 g−1 min−1) by catalysing the hydrolysis of sodium borohydride using magnetic actuation.

We study the optimization of the catalytic properties of entirely magnetic Co-Pt compact and mesoporous nanowires of different diameters (25-200 nm) by using magnetic actuation. The nanowires are a single-entity, robust, magnetic-catalyst with a huge catalytically-active surface area. We show that apart from conventional parameters, like the size and morphology of the nanowires, other factors can be optimized to enhance their catalytic activity. In particular, given the magnetic character of the nanowires, rotating magnetic fields are a very powerful approach to boost the performance of the catalyst. In particular, the magnetic field induces them to act as nano-stirrers, improving the local flow of material towards the active sites of the catalyst. We demonstrate the versatility of the procedure by optimizing (i) the degradation of different types of pollutants (4-nitrophenol and methylene blue) and (ii) hydrogen production. For example, by using as little as 0.1 mg mL−1 of 25 nm wide Co-Pt mesoporous nanowires (with ∼3 nm pore size) as catalysts, kinetic normalized constants knor as high as 20,667 and 21,750 s−1 g−1 for 4-nitrophenol and methylene blue reduction, respectively, are obtained. In addition, activity values for hydrogen production from borohydride are as high as 25.0 L H2 g−1 min−1, even at room temperature. These values outperform any current state-of-the-art proposed catalysis strategies for water remediation reactions by at least 10-times and are superior to most advanced approaches to generate hydrogen from borohydride. The recyclability of the nanowires together with the simplicity of the synthetic method makes this approach (using not only Co-Pt, but also other mesoporous magnetic catalysts) very appealing for very diverse types of catalytic applications.

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