BN nanoparticle/Ag hybrids with enhanced catalytic activity: theory and experiments

Abstract

Hexagonal boron nitride nanoparticles (BNNPs) with different amounts of boron oxide on their surfaces were used as catalyst carriers. BNNPs/Ag nanohybrids were produced via ultraviolet (UV) decomposition of AgNO₃ in a mixture of polyethylene glycol and BNNPs. High temperature (1600 °C, 1.5 h) vacuum annealing of BNNPs promoted small size (5–10 nm) Ag nanoparticle (AgNPs) formation on BN surfaces with narrow size distribution, whereas using BNNPs in their as-produced state resulted in large AgNPs with various sizes. An increase in the B₂O₃ content on the BNNPs surfaces (up to a certain point) during BNNP pre-annealing in air led to larger amounts of AgNPs on their surfaces. Experimental results were confirmed by theoretical calculations of the adhesion energy of the (111)_Ag with (0001)_h-BN and (100)_B2O3 surfaces. In contrast to the nonwettability of the h-BN surface by AgNPs, silver bound well to B₂O₃ with the formation of a covalent bond at the interface. Excessive fraction of B₂O₃, however, was not beneficial in terms of obtaining the optimal contents of AgNPs. Results of catalytic activity tests demonstrated that BNNPs/Ag nanohybrids synthesized using BNNPs with an optimized amount of B₂O₃ possess significantly enhanced catalytic activity compared to BNNPs without or with excess amounts of oxide. Finally, the catalytic activity of nanohybrids was theoretically analyzed using density functional theory (DFT) calculations.