Prioritizing key determinants of hematite photocatalysis through structure – Property contour mapping and statistical correlation analysis
Journal
Process Safety and Environmental Protection
Journal Volume
208
Start Page
108519
ISSN
0957-5820
Date Issued
2026-03
Author(s)
Wang, TsingHai
Chen, Ching-Lung
Kuan, Wei-Fan
Li, Wei-Tong
Ke, Ching-Yao
Lin, Tzu-Han
Fuh, Huei-Ru
Abstract
Understanding which structural and electronic descriptors primarily govern the photocatalytic reactivity of hematite remains challenging due to the complex interplay among lattice defects, band-structure modulation, and surface redox chemistry. This study aims to identify and quantitatively prioritize the key physicochemical factors that control hematite photocatalysis, rather than to determine a single optimal synthesis condition. Mn-doped hematite (α−Fe2O3) was selected as a model system and synthesized over varying Mn contents (up to 10 mol%) and calcination temperatures (400 −800 ℃). The materials were systematically characterized by XRD, Raman spectroscopy, XPS, and UV–vis analyses. Structure–property contour mapping was then integrated with Pearson correlation analysis to evaluate photocatalytic methylene blue degradation. Among all descriptors examined, band gap energy is identified as the strongest determinant of photocatalytic reactivity (r = −0.818, p < 0.001). The surface Fe(II)/Fe(III) ratio ranks as the second most influential factor (r = 0.555, p = 0.026), followed by the average lattice strain (r = −0.391, p = 0.134). These results indicate that electronic structure modulation and defect-related lattice distortion play more dominant roles than crystallite size or plane-specific strain. Contour analysis further reveals that pronounced band gap narrowing consistently occurs once Mn doping exceeds 5 mo% across all investigated calcination temperatures. In contrast, elevated surface Fe(II)/Fe(III) ratios emerge primarily under conditions combining both high Mn doping and high calcination temperature. These two descriptors therefore exhibit distinct but complementary statistical correlations with photocatalytic removal efficiency and apparent reaction kinetics. Rather than identifying a single optimal Mn content and calcination temperature, the statistical analysis highlight band gap narrowing and surface Fe redox state as the most transferable performance-governing descriptors. Collectively, this study establishes a descriptor-prioritization-based structure–activity framework, in which photocatalytic performance is most strongly associated with defect-mediated electronic structure modulation and surface Fe(III)/Fe(II) characteristics. This framework provides practical guidance for the rational design of hematite-based photocatalysts for low-carbon and sustainable wastewater treatment.
Subjects
Band gap
Hematite
Photocatalyst
Statistical correlation analysis
Surface Fe(II)/Fe(III) ratio
Publisher
Institution of Chemical Engineers
Description
Article number 108519
Type
journal article