In situ conversion of Co–CoN nanowires into ultrathin 2D nanosheets for highly effective catalytic hydrogenation

Abstract

The design of two-dimensional (2D) CoN-based thin sheets is promising in the catalytic field. The typical synthesis based on the thermal treatment of the hydroxide sheets results in enhanced particle size and thick sheets. Here, we show a novel route based on in situ conversion of Co–CoN nanowires into ultra-thin sheets for effective catalytic hydrogenation. The Co–CoN nanowires were first prepared by the pyrolysis of 1D cobalt-nitrilotriacetic acid nanowires (Co-NTA NWs) and used for the catalytic hydrogenation of p-nitrophenol (P-NP) into p-aminophenol (P-AP) in the presence of NaBH₄. Unexpectedly, during the second catalytic run, the catalytic activity showed an obvious enhancement with a conversion rate of 99% within 60 seconds, which was better than the time of 90 seconds in the first use. The improved activity should be related to the formation of thin nanosheets. A further study of the catalyst showed the in situ formation of Co–CoN thin sheets on nanowires during the catalytic reaction. The sequential conversion from nanowires to nanosheets–nanowires and then to the final thin sheets was demonstrated. The presence of the NaBH₄ and P-NP is key to promote the conversion. The performance shows no obvious change after continuous catalysis for seven cycles. The in situ conversion synthesis will be instructive for the design of other functional catalysts through an induced conversion process.