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Liu et al. J Mater Inf 2024;4:33 https://dx.doi.org/10.20517/jmi.2024.48 Page 5 of 33

Table 1. Key characteristics of photocatalysts and typical characterization techniques
Characteristics Typical characterization technique
Microstructure Grain size SEM TEM DLS AFM
Specific surface area BET BJH MIP
Pore size BET SAXS
Facet XRD TEM
Lattice symmetry XRD Neutron diffraction
Space group XRD Electron diffraction
Architecture Quantum dot PL HRTEM AC-TEM
Nanowire SEM TEM AFM
Single few-layer nanostructure AFM HRTEM
Heterojunction EELS STEM
Composition Stoichiometry EDS ICP-MS ICP-OES XPS
Doping element XPS EELS
Defect PALS HRTEM
Functional group FTIR XPS SIMS
Electronic structure Band structure XPS ARPES
DOS XPS
Electron affinity UPS
Electron spin ESR EPR XMCD
Band gap UV-Vis PL
VBM XPS UPS
CBM XPS
Photoelectric property Absorption UV-Vis DRS
Carrier mobility Hall effect analysis Seebeck coefficient
Carrier lifetime TRPL
Photocurrent density LSV j-V curve
Quantum yield PL

DOS: Density of states; VBM: valence band maximum; CBM: conduction band minimum; SEM: Scanning electron microscopy; TEM: transmission
electron microscopy; DLS: dynamic light scattering; AFM: atomic force microscopy; BET: Brunauer-Emmett-Teller measurements; BJH: Barret-
Joyner-Halenda measurements; MIP: molecularly imprinted polymer; SAXS: small angle x-ray scattering; PL: photoluminescence; HRTEM: high-
resolution transition electron microscopy; AC-TEM: spherical aberration corrected transmission electron microscopy; EELS: electron energy loss
spectroscopy; STEM: scanning transmission electron microscopy; ICP-MS: inductively coupled plasma mass spectrometry; ICP-OES: inductively
coupled plasma-optical emission spectrometry; XPS: X-ray photoelectron spectroscopy; PALS: positron annihilation spectroscopy; FTIR: Fourier
transform infrared spectroscopy; SIMS: Secondary-ion-mass spectroscopy; ARPES: angle-resolved photoemission spectroscopy; UPS: ultraviolet
photoelectron spectroscopy; ESR: electron spin resonance; EPR: electron paramagnetic resonance; XMCD: X-ray magnetic circular dichroism; UV-
Vis: ultraviolet-visible absorbance spectra; DRS: diffuse reflection spectroscopy; TRPL: time-resolved photoluminescence; LSV: linear sweep
voltammetry.

Traditional procedure of photocatalyst design
Traditional photocatalyst design has predominantly relied on empirical methods, where photocatalysts are
synthesized and evaluated through trial-and-error experimentation. The process typically begins with
selecting semiconductors based on properties such as band gap and chemical stability, which indicate
potential photocatalytic activity. Techniques such as sol-gel synthesis , hydrothermal methods , or
[61]
[62]
chemical vapor deposition [63,64] are commonly used to fabricate photocatalysts. After synthesis, thorough
characterization is conducted using methods such as transmission electron microscopy (TEM), X-ray
photoelectron spectroscopy (XPS), and ultraviolet-visible absorbance spectra (UV-Vis) spectroscopy to
assess key features such as morphology, electronic structure, and light absorption properties. The
photocatalysts are then tested under controlled laboratory conditions to determine their efficiency in
processes such as pollutant degradation or water splitting.