Alumina-Supported CoFe Alloy Catalysts Derived from Layered-Double-Hydroxide Nanosheets for Efficient Photothermal CO2 Hydrogenation to Hydrocarbons

Abstract

A series of novel CoFe-based catalysts are successfully fabricated by hydrogen reduction of CoFeAl layered-double-hydroxide (LDH) nanosheets at 300–700 °C. The chemical composition and morphology of the reaction products (denoted herein as CoFe-x) are highly dependent on the reduction temperature (x). CO₂ hydrogenation experiments are conducted on the CoFe-x catalysts under UV–vis excitation. With increasing LDH-nanosheet reduction temperature, the CoFe-x catalysts show a progressive selectivity shift from CO to CH₄, and eventually to high-value hydrocarbons (C₂₊). CoFe-650 shows remarkable selectivity toward hydrocarbons (60% CH₄, 35% C₂₊). X-ray absorption fine structure, high-resolution transmission electron microscopy, Mössbauer spectroscopy, and density functional theory calculations demonstrate that alumina-supported CoFe-alloy nanoparticles are responsible for the high selectivity of CoFe-650 for C₂₊ hydrocarbons, also allowing exploitation of photothermal effects. This study demonstrates a vibrant new catalyst platform for harnessing clean, abundant solar-energy to produce valuable chemicals and fuels from CO₂.

Three unique CoFe-based catalysts are successfully fabricated via direct H₂ reduction of a CoFeAl layered-double-hydroxide (CoFeAl-LDH) nanosheets precursor by varying the reduction temperature. LDH precursor reduction at temperatures above 600 °C results in the formation of CoFe-alloy nanoparticles, thereby affording a remarkable CO₂ hydrogenation selectivity toward high-value (C₂₊) hydrocarbons under simulated solar excitation through photothermal effects.

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