Heterojunction constructions are usually used to promote the separation of photocarriers and improve the photocatalytic activities. However, misuse and confusion often occur in current research because there are no unified rules for the classification and naming of heterojunctions. In order to avoid this problem, this review summarizes and standardizes the classification and naming rules of heterojunctions, based on different band structure distribution of the two semiconductors in heterojunctions and transfer paths of photogenerated carriers. Moreover, the distinctions in photogenerated carrier behavior among O–scheme heterojunction, Z–scheme heterojunction, and S–scheme heterojunction within type II heterojunction are clearly elucidated. Additionally, current methodologies for identifying heterojunction types, including metal–ion photo–deposition, in situ X–ray photoelectron spectroscopy, surface photovoltage spectroscopy, transient absorption spectroscopy, and cathodoluminescence spectrometry, are summarized. This review also highlights the applicability of various heterojunction types across different photocatalytic applications and suggests future directions for heterojunction research.

The selective oxidation of methane to high value‐added liquid oxygenated compounds under mild conditions is of great significance to promote the efficient utilization of the carbon source, but it also faces the dilemma of low activity and over‐oxidation. Here, ZnTi‐layered double hydroxides (LDH)‐A200 photocatalysts with Pd loading are prepared to achieve efficient oxidation of methane, with O₂ as an oxidant under ambient condition. The highest generation rate of C₁ liquid products (methanol and formaldehyde) reaches 4924.47 µmol g⁻¹ h⁻¹ with a selectivity close to 100% over 0.5Pd‐ZnTi‐LDH‐A200, which is 20 times higher than that of bare ZnTi‐LDH‐A200. The photochemical results show that the modified photocatalysts present much higher generation and separation efficiency of electron‐hole pairs. In situ X–ray photoelectron spectroscopy indicates that Pd nanoparticles are the hole acceptor, which is beneficial to charge separation in the photocatalysis. Furthermore, electron spinresonance spectroscopy and temperature–programmed–desorption analysis prove that Pd loading is helpful to the adsorption of methane and oxygen on the surface of ZnTi‐LDH‐A200, promoting the production of reactive oxygen species and activation of methane. All these factors work together to promote the efficient conversion of CH₄ to high value‐added C₁ oxygenates.