Wafer-Level Artificial Photosynthesis for CO<sub>2</sub> Reduction into CH<sub>4</sub> and CO Using GaN Nanowires
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Abstract
We report on the first demonstration
of high-conversion-rate photochemical
reduction of carbon dioxide (CO<sub>2</sub>) on gallium nitride (GaN)
nanowire arrays into methane (CH<sub>4</sub>) and carbon monoxide
(CO). It was observed that the reduction of CO<sub>2</sub> to CO dominates
on as-grown GaN nanowires under ultraviolet light irradiation. However,
the production of CH<sub>4</sub> is significantly increased by using
the Rh/Cr<sub>2</sub>O<sub>3</sub> core/shell cocatalyst, with an
average rate of ∼3.5 μmol g<sub>cat</sub><sup>–1</sup> h<sup>–1</sup> in 24 h. In this process, the rate of CO<sub>2</sub> to CO conversion is suppressed by nearly an order of magnitude.
The rate of photoreduction of CO<sub>2</sub> to CH<sub>4</sub> can
be further enhanced and can reach ∼14.8 μmol g<sub>cat</sub><sup>–1</sup> h<sup>–1</sup> by promoting Pt nanoparticles
on the lateral <i>m</i>-plane surfaces of GaN nanowires,
which is nearly an order of magnitude higher than that measured on
as-grown GaN nanowire arrays. This work establishes the potential
use of metal-nitride nanowire arrays as a highly efficient photocatalyst
for the direct photoreduction of CO<sub>2</sub> into chemical fuels.
It also reveals the potential of engineered core/shell cocatalysts
in improving the selectivity toward more valuable fuels