Ki‐Hyun Kim
ABSTRACT The absence of standardized diagnostic protocols has fostered widespread mechanistic uncertainty in heterojunction photocatalysis, with numerous Type‐II claims lacking conclusive interfacial and kinetic evidence. In response, I propose a three‐phase, seven‐step diagnostic framework structured as an evidence hierarchy: Phase I (Steps 1–3) establishes foundational band alignment, Phase II (Steps 4–5) probes the interfacial electronic structure, and Phase III (Steps 6–7) validates dynamic charge‐transfer pathways. An evaluation of 30 purported Type‐II systems reveals a critical validation gap: only 3.3% (1/30) achieves full validation, leaving 10.0% (3/30) characterized as thermodynamic paradoxes (electrical sign‐reversals) and 86.7% (26/30) in a pervasive evidence vacuum (stalling at foundational alignment). This protocol is offered as a diagnostic tool to help the field move from heuristic assignment toward more evidence‐based rational design of photocatalysts.