Reversed Charge Transfer Enables Dual Active Sites on Ir/hBN for Synergistic N<sub>2</sub>O Valorization and Propane Selective Oxidation
Yunshuo Wu, Yuxin Sun, Xuanhao Wu, Haiqiang Wang, Zhongbiao Wu
Abstract
Valorization of nitrous oxide (N 2 O) as a mild oxygen source for light alkanes presents a promising and economical method for mitigating global warming. However, activating N 2 O and alkane together often leads to overoxidation and poor selectivity of the products. To disentangle the trade-off between activity and selectivity, herein, an Ir-based hexagonal boron nitride (hBN) catalyst was synthesized to obtain a reversed charge transfer (RCT) from the support to metal centers, forming dual active sites on Ir clusters and the separation of redox centers, as determined via operando near-ambient-pressure X-ray photoelectron spectroscopy (NAP-XPS) and density functional theory (DFT) calculations. Ir/hBN demonstrated a high N 2 O conversion (99.5%) and syngas yield (95.9 mol of CO kg cat –1 h –1 and 41.9 mol of H 2 kg cat –1 h –1 ) during the selective oxidation of propane (C 3 H 8 ) at 450 °C. The electron-rich Ir interfacial perimeter sites (Ir δ− ) enhance N 2 O adsorption and N–O bond dissociation to produce active O*; however, facial metallic Ir 0 sites effectively facilitate C 3 H 8 activation, including dehydrogenation and cracking. The separation of H* and O* intermediates, along with the frustrated H*/O* spillover, effectively facilitates the formation of H 2 . The *CH 2 intermediate from C 3 H 8 breakage migrates and reacts with O* bound to Ir interfacial sites, where it is oxidized to CO 3 2– and subsequently liberates CO. This study provides mechanistic insights into the O element valorization from N 2 O with synergetic enhancement in selective oxidation of light alkanes.