Dual-scheme heterojunctions in photocatalysis: A bibliometric and network analysis of the research landscape (2020–2025)

Dual-scheme heterojunction photocatalysts, which integrate two independent charge-transfer pathways within a single composite to combine strong redox capability with efficient electron–hole separation, have emerged as a fast-growing family of solar-driven materials for environmental remediation and clean-fuel generation. This study provides a comprehensive bibliometric and network analysis of the field. Using a targeted Web of Science Topic query designed to capture all classes of dual-scheme system (same-type dual S- and Z-schemes, dual step-scheme, dual Type-II, p–n and Schottky configurations, and mixed scheme–junction combinations), gated to photocatalysis, 856 research articles published between 2020–2025 were retrieved and analysed. Annual output grew from 53 articles in 2020 to 247 in 2025, a compound annual growth rate of 36.05%, accumulating 29,497 Web of Science citations with a collection h-index of 80. Output is concentrated in applied catalysis and environmental journals and is geographically dominated by China, with India, Saudi Arabia, Iran and South Korea forming a secondary tier. Co-word and thematic (Callon strategic diagram) analyses reveal an intellectual core organised around dual Z-scheme and S-scheme heterojunctions coupled with g-C₃N₄-based photocatalysts, with well-developed sub-themes in pollutant degradation and photocatalytic hydrogen evolution. Trend-topic dating, cross-checked against the VOSviewer temporal overlay, identifies oxygen-vacancy engineering (median year 2024) as the current emerging frontier. Country collaboration is a China-centred hub-and-spoke, whereas the author collaboration network is fragmented into distinct national groups. The results provide a quantitative baseline for the emerging dual-scheme heterojunction literature and identify concrete opportunities in mixed-scheme designs, defect engineering and international collaboration.