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Mixed phases of GaOOH/β-GaO and α-GaO/β-GaO prepared by high energy ball milling as active photocatalysts for CO reduction with water
The photocatalytic activity of mixed phases of GaOOH/β-Ga 2 O 3 and α-Ga 2 O 3 /β-Ga 2 O 3 for CO 2 reduction with water is investigated for the first time. GaOOH/β-Ga 2 O 3 is synthesized by high energy ball milling of β-Ga 2 O 3 in water, and α-Ga 2 O 3 /β-Ga 2 O 3 are prepared by the calcination...
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| Published in: | New journal of chemistry 2022-02, Vol.46 (7), p.327-3213 |
|---|---|
| Main Authors: | , , , |
| Format: | Article |
| Language: | |
| Online Access: | Get full text |
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| Summary: | The photocatalytic activity of mixed phases of GaOOH/β-Ga
2
O
3
and α-Ga
2
O
3
/β-Ga
2
O
3
for CO
2
reduction with water is investigated for the first time. GaOOH/β-Ga
2
O
3
is synthesized by high energy ball milling of β-Ga
2
O
3
in water, and α-Ga
2
O
3
/β-Ga
2
O
3
are prepared by the calcination of GaOOH/β-Ga
2
O
3
at 773 K. Both show higher activity for both CO
2
reduction and the accompanying H
2
evolution than the original material of β-Ga
2
O
3
. This is the first observation that the mixed phase of GaOOH/β-Ga
2
O
3
has high photocatalytic activity. The H
2
production rate is correlated to the specific surface area irrespective of the GaOOH/β-Ga
2
O
3
and α-Ga
2
O
3
/β-Ga
2
O
3
samples. The CO production rate for the mixed phase of α-Ga
2
O
3
/β-Ga
2
O
3
is high, agreeing with the previous observation that the mixed phases or phase boundaries enhance the photocatalytic activity, and the CO production rate increases with the abundance rate of the α-Ga
2
O
3
phase. Although the selectivity of the CO production remains low, it could be enhanced if an Ag cocatalyst was used. As an alternative mechanism of H
2
production (H
2
evolution) over the samples of GaOOH/β-Ga
2
O
3
and α-Ga
2
O
3
/β-Ga
2
O
3
, a redox type reaction mechanism is proposed, in which the H
2
evolution proceeds with the reduction of GaOOH to α-Ga
2
O
3
emitting H
2
and O
2
by UV illumination, while α-Ga
2
O
3
returned to GaOOH in water without illumination. Although some of the H
2
thus evolved would cause CO
2
reduction, CO
2
reduction to CO requires specific active sites on the α-Ga
2
O
3
surface.
The H
2
production rates increased with SSA, irrespective of the phases, while the CO production rates increased with the abundance of α-Ga
2
O
3
. |
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| ISSN: | 1144-0546 1369-9261 |
| DOI: | 10.1039/d1nj05245d |