  Excessive CO2 emission from fossil fuel usage has resulted in global warming
and environmental crises. To solve this problem, the photocatalytic conversion
of CO2 to CO or useful components is a new strategy that has received
significant attention. The main challenge in this regard is exploring
photocatalysts with high efficiency for CO2 photoreduction. Severe plastic
deformation (SPD) through the high-pressure torsion (HPT) process has been
effectively used in recent years to develop novel active catalysts for CO2
conversion. These active photocatalysts have been designed based on four main
strategies: (i) oxygen vacancy and strain engineering, (ii) stabilization of
high-pressure phases, (iii) synthesis of defective high-entropy oxides, and
(iv) synthesis of low-bandgap high-entropy oxynitrides. These strategies can
enhance the photocatalytic efficiency compared with conventional and benchmark
photocatalysts by improving CO2 adsorption, increasing light absorbance,
aligning the band structure, narrowing the bandgap, accelerating the charge
carrier migration, suppressing the recombination rate of electrons and holes,
and providing active sites for photocatalytic reactions. This article reviews
recent progress in the application of SPD to develop functional ceramics for
photocatalytic CO2 conversion.
