We demonstrate the viability of the In2O3/In2S3 heterojunction for efficient
photocatalytic
H2 evolution from a formaldehyde aqueous solution, which
is an alternative renewable hydrogen source, in a direct Z-scheme
manner under visible light without any electron mediator and cocatalyst.
The optimal In2O3/In2S3 heterojunction shows a fast hydrogen evolution rate of 6.16 mmol·g–1·h–1, which is approximately
166 times and 6 times higher than that of pure In2O3 and pure In2S3, respectively. The superior
photocatalytic activity of the In2O3/In2S3 heterojunction compared to single-component
In2O3 and In2S3 is attributed
to its appropriate band gap, enhanced charge separation, and transfer
abilities, as attested by various spectroscopic characterization and
photoelectrochemistry experiments. Among the different fabrication
approaches, the sequential hydrothermal–calcination technique,
which produces a hydrangea-like morphology, affords the most active
In2O3/In2S3 heterojunction
photocatalyst. Molecular O2 is found to play a key role
in instigating the photocatalytic H2 evolution from formaldehyde
oxidation as a catalytic electron scavenger, which is not consumed
throughout the reaction.