Catalytic reduction of bromate by Co-embedded N-doped carbon as a magnetic Non-Noble metal hydrogenation catalyst

Abstract

While catalytic hydrogenation of bromate represents a useful technique for eliminating carcinogenic bromate, expensive noble-metal catalysts and excessive H2 gas are usually required, impeding large-scale implementation of this technique. As borohydride is an alternative source for releasing H2 in a more controllable way and nonnoble metal catalysts (e.g., Co) can catalyze hydrolysis of borohydride to generate H2, it is promising to employ Co and borohydride for hydrogenation of bromate. Moreover, it is even more practical to develop heterogeneous catalysts with magnetism for easier handle and recovery of catalysts. Therefore, the aim of this study is to develop such a magnetic heterogeneous catalyst for bromate reduction by using borohydride. Herein, a special Co-based catalyst is fabricated by transforming Co-substituted prussian blue analogue into Co-embedded Ndoped carbon (Co@NC) composite through carbonization. Co@NC also exhibits a higher catalytic activity for reducing bromate than the commercial Co3O4 as Co@NC could accelerate hydrolysis of NaBH4 to generate H2 gas much faster. The activation energy (Ea) of bromate reduction by Co@NC is also much lower than the reported Ea. Co@NC could still completely remove bromate and reduce it to bromide under alkaline conditions, and Co@NC also exhibit a very high selectivity towards bromate reduction in the presence of other anions. Moreover, Co@NC could be also reused for multiple-cycles to continuously reduce bromate to bromide. These features demonstrate that Co@NC is certainly an advantageous and convenient heterogeneous catalyst for reducing bromate in water.