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Page 4 of 33 Liu et al. J Mater Inf 2024;4:33 https://dx.doi.org/10.20517/jmi.2024.48

photocatalysis is primarily governed by critical factors such as charge carrier separation, charge mobility,
[36]
and the efficient suppression of electron-hole recombination . Figure 1 presents an in-depth depiction of
the pathways undertaken by photogenerated charge carriers, emphasizing the intricate redox reactions
occurring at the photocatalyst surface, alongside recombination processes occurring both within the bulk
and at the surface.

The core of photocatalysis lies in the photocatalysts. Traditional photocatalysts are typically bulk
semiconductors that harness light to drive photocatalytic reactions, but they often suffer from low
[38]
efficiency due to limited surface area and rapid recombination of charge carriers. Nanostructured
photocatalysts , on the other hand, offer significantly enhanced performance due to their increased surface
[39]
area and improved charge carrier dynamics, which help reduce recombination and enhance photocatalytic
activity. Heterojunction systems [40,41] combine two or more semiconductors with different band structures,
creating interfaces that facilitate more efficient charge separation and transfer, thus improving overall
[43]
efficiency. Low-dimensional systems, such as quantum dots , one-dimensional , and two-dimensional
[42]
(2D) structures [44,45] , exhibit unique quantum confinement effects that significantly alter their electronic
properties. Quantum dots have tunable band gaps due to their nanoscale dimensions, enabling enhanced
light absorption and charge separation . One-dimensional structures, including nanowires or nanotubes,
[46]
[47]
provide high charge carrier mobility along their axial direction to improve performances . 2D systems
feature high surface-to-volume ratios and exceptional electronic properties, offering more active sites for
photocatalytic reactions .
[48]

The performance of photocatalysts is critically determined by several key characteristics, each influencing
different aspects of photocatalytic efficiency. (1) The microstructure, including grain size, specific surface
area, and pore size, directly affects the availability of active sites and the overall surface reactivity; (2)
Architecture factors, such as quantum dots, nanowires, and heterojunctions, influence light absorption and
charge separation, with more advanced structural designs often improving charge transportation; (3)
Composition, including stoichiometry, doping elements, and the presence of defects, plays a pivotal role in
tuning electronic properties, thereby optimizing light absorption, charge carrier dynamics, and redox
processes; (4) The electronic structure, particularly the band gap, density of states (DOS), and electron
affinity, dictates the ability to absorb irradiation energy and generate charge carriers, which are essential for
driving photocatalytic reactions; (5) Photoelectric properties, such as carrier mobility, carrier lifetime, and
quantum yield, determine the effectiveness of converting absorbed light into chemical energy. Higher
mobility and longer carrier lifetimes facilitate more efficient charge separation and reduce recombination.
Table 1 lists the key characteristics of photocatalysts and their typical characterization techniques.

Common modification strategies for photocatalysts include doping , cocatalyst loading and
[50]
[49]
incorporating single-atom catalysts [51,52] . Latest modification mechanisms, such as defect engineering, band
structure engineering, and interfacial engineering, enable precise control at the atomic, electronic, and
chemical bond levels, significantly enhancing photocatalytic performance [53,54] . Recently, constructing
heterojunctions [55,56] remains a major focus of research, with types including Type I, Type II, Z-scheme, and
S-scheme heterojunctions being extensively studied. In particular, S-scheme heterojunctions offer distinct
advantages [57,58] , such as optimized band alignment and enhanced charge separation, which contribute to
superior redox capabilities and reduced electron-hole recombination, making them highly promising for
practical applications . For instance, in ribbon-based water purification, these modification strategies have
[59]
been instrumental in enhancing photocatalytic degradation efficiency by improving charge carrier
dynamics, optimizing active sites, and facilitating the breakdown of complex organic pollutants, thereby
demonstrating significantly superior performance .
[60]