Development of Au and 1D Hydroxyapatite Nanohybrids Supported on 2D Boron Nitride Sheets as Highly Efficient Catalysts for Dehydrogenating Glycerol to Lactic Acid

In this study, highly transparent and tightly packed two-dimensional boron nitride (2D BN NSs) nanosheets were prepared using an eco-friendly green-template-assisted synthesis method, where a banana stem powder was used as the bio template. Microscopic results indicated that 2D BN NSs mostly consisted of thin layers, with lateral sizes of 0.5 to 2 μm. Further, strongly coupled dual catalytic sites of 0D Au and c-axis oriented 1D hexagonal hydroxyapatite (HAp) nanorods were successfully immobilized and uniformly distributed on the surfaces of 2D BN NSs (Au/HAp/BN). A detailed study of Au/HAp/BN formation mechanism is presented in this paper. This study showed that due to the intriguing morphological, structural, and compositional features of Au/HAp/BN ternary nanohybrids, they can be used as an efficient heterogeneous catalytic oxidation system for oxidizing glycerol into lactic acid. In particular, the localized surface of BN was shown to exhibit high affinity toward adsorbing glycerol via higher adsorption affinity; therefore, an oxidizing reaction was obtained at the dual catalytic sites of Au and HAp in the heterogeneous catalytic system of Au/HAp/BN. On the Au/HAp/BN catalyst, 100% glycerol conversion yield was obtained with a high selective production of lactic acid (99.5%) in its base condition at a temperature of 100 °C. Different effects of the NaOH-glycerol molar ratio, reaction time of the catalytic activity, and selectivity of the Au/HAp/BN catalyst suggested that the dual-route reaction pathway was responsible for dehydrating glycerol to lactic acid; this has been elucidated in the paper. Reusability experiments showed the chemical stability and prolonged usage of the Au/HAp/BN catalyst, which can be beneficial for industrial applications.