Reductive Transformation of Layered-Double-Hydroxide Nanosheets to Fe-Based Heterostructures for Efficient Visible-Light Photocatalytic Hydrogenation of CO

Abstract

Conversion of syngas (CO, H₂ ) to hydrocarbons, commonly known as the Fischer-Tropsch (FT) synthesis, represents a fundamental pillar in today's chemical industry and is typically carried out under technically demanding conditions (1-3 MPa, 300-400 °C). Photocatalysis using sunlight offers an alternative and potentially more sustainable approach for the transformation of small molecules (H₂ O, CO, CO₂ , N₂ , etc.) to high-valuable products, including hydrocarbons. Herein, a novel series of Fe-based heterostructured photocatalysts (Fe-x) is successfully fabricated via H₂ reduction of ZnFeAl-layered double hydroxide (LDH) nanosheets at temperatures (x) in the range 300-650 °C. At a reduction temperature of 500 °C, the heterostructured photocatalyst formed (Fe-500) consists of Fe⁰ and FeO_x nanoparticles supported by ZnO and amorphous Al₂ O₃ . Fe-500 demonstrates remarkable CO hydrogenation performance with very high initial selectivities toward hydrocarbons (89%) and especially light olefins (42%), and a very low selectivity towards CO₂ (11%). The intimate and abundant interfacial contacts between metallic Fe⁰ and FeO_x in the Fe-500 photocatalyst underpins its outstanding photocatalytic performance. The photocatalytic production of high-value light olefins with suppressed CO₂ selectivity from CO hydrogenation is demonstrated here.

Keywords: CO hydrogenation; Fe-based catalysts; layered double hydroxides; light olefins; photocatalysis.