posted on 2021-10-19, 17:17authored byPeng Chen, Kanglu Li, Ben Lei, Lvcun Chen, Wen Cui, Yanjuan Sun, Wendong Zhang, Ying Zhou, Fan Dong
Differentiated
crystal structures generally affect the surface
physicochemical properties of catalysts, causing variety in catalytic
activity between polymorphs. However, the underlying mechanism has
not been completely revealed, especially the influence of surface
physicochemical properties on photocatalytic redox activity and the
reaction mechanism. In this work, we reveal the mechanism of surface
redox properties on different crystal forms of gallium oxide from
a molecular level. α-Ga2O3 and β-Ga2O3 exhibit a slight difference in catalytic oxidation
of organic pollutants due to comprehensive influencing factors, including
their valence band position, reactive oxygen species, and pore structure
properties related to the adsorption–reaction–desorption
process. But the catalytic reduction ability of CO2 is
obviously different due to the large differences of interaction between
the surface of crystal structures and CO2 molecules, which
are critical to determine the catalytic performance and reaction pathways.
The enhanced adsorption and activation of CO2 on the α-Ga2O3 surface could promote the reduction reaction
efficiency. Moreover, the large energy barrier of CH2*
formation on β-Ga2O3 makes the formation
of methane (CH4) relatively difficult compared to that
on α-Ga2O3. The yield rate of CH4 (1.8 μmol·g–1·h–1) on α-Ga2O3 is three times better than
that on β-Ga2O3 (CH4: 0.6 μmol·g–1·h–1). The current findings
can offer novel insights into the understanding of crystal-structure-dependent
photocatalytic performances and the design of new catalysts applied
in energy conversion and environmental purification by crystal structure-tuning.