Ambient-Pressure C-C Coupling of CO Hydrogenation by NiFe/TiO Bimetallic Catalyst.

Catalytic upgrading of CO to value-added C 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 pretreatment temperature. An optimal performance was achieved after reducing NiFe/TiO at 350 °C (NiFe-350/TiO), yielding 27.8% CO conversion and 33.9% selectivity to C-C hydrocarbon (primarily ethane) at 350 °C under atmospheric pressure. Combinatorial studies employing characterizations, kinetic, intermediate control experiments and calculations indicate the formation of partially oxidized Ni-O-Fe in NiFe-350/TiO, the dual-site synergy of which enhances CO activation and facilitates H heterolytic activation into H species that selectively hydrogenate *CO into HCOO* and *CHO intermediates, thus suppressing CO byproduct formation and resulting in effective ambient-pressure C-C coupling likely via an asymmetric *CH-CH coupling mechanism. In stark contrast, the fully reduced NiFe bimetallic catalyst favors a direct CO dissociation pathway instead to form *CO that easily desorbs from the surface, as well as homolytic H activation such that the C-C coupling process is unfavored. In brief, this work reports the ambient-pressure synthesis of C-C paraffins from direct CO hydrogenation and provides design rationales for efficient carbon chain propagation.