Ambient-Pressure C–C Coupling of CO<sub>2</sub> Hydrogenation by NiFe/TiO<sub>2</sub> Bimetallic Catalyst
Mingxin Jiang, Zhi-Qiang Wang, Zhuo Li, Zhisong Liu, Yiwei Yin, Fei-Xiang Tian, Anyu Li, Haomiao Xu, Xue‐Qing Gong, Yulian He
Abstract
Catalytic upgrading of CO 2 to value-added C 2+ products offers promising solutions to trim carbon emissions with additional economic benefits. Herein, we report a NiFe bimetallic catalyst showing efficient ambient-pressure C–C coupling performance subject to H 2 pretreatment temperature. An optimal performance was achieved after reducing NiFe/TiO 2 at 350 °C (NiFe-350/TiO 2 ), yielding 27.8% CO 2 conversion and 33.9% selectivity to C 2 –C 3 hydrocarbon (primarily ethane) at 350 °C under atmospheric pressure. Combinatorial studies employing in situ characterizations, kinetic, intermediate control experiments and first-principles calculations indicate the formation of partially oxidized Ni δ+ –O–Fe δ+ in NiFe-350/TiO 2, the dual-site synergy of which enhances CO 2 activation and facilitates H 2 heterolytic activation into H δ− species that selectively hydrogenate *CO 2 into HCOO* and *CH 3 O intermediates, thus suppressing CO byproduct formation and resulting in effective ambient-pressure C–C coupling likely via an asymmetric *CH 2 –CH 3 coupling mechanism. In stark contrast, the fully reduced NiFe bimetallic catalyst favors a direct CO 2 dissociation pathway instead to form *CO that easily desorbs from the surface, as well as homolytic H 2 activation such that the C–C coupling process is unfavored. In brief, this work reports the ambient-pressure synthesis of C 2 –C 3 paraffins from direct CO 2 hydrogenation and provides design rationales for efficient carbon chain propagation.