Defect engineering is a widely used strategy for tailoring the band structures and surface-active sites of tungsten trioxides (WO3) nanomaterials, thereby enhancing their photocatalytic performance. In particular, precise control of defect topology is recognized as a pivotal step in constructing surface-active sites, enabling the regulation of surface atomic configurations through the deliberate design of defect types and their terminations. This mini-review elucidates the roles of various surface defect types of WO3 semiconductors in photocatalytic redox reactions, revealing how surface defect topology activates reactants at the atomic level. It aims to provide insightful information on defective photocatalysts to guide the optimization of the electronic structures inside photocatalysts, thereby establishing a computational-experimental framework for next-generation adaptive photocatalyst architectures.

Photocatalytic H2O2 production using organic photoactive materials provides a sustainable route for solar-driven oxidant synthesis. However, high efficiency and selectivity require more than effective charge separation. Photogenerated carriers must be properly matched with reactive species, catalytic sites, and transport processes. Here, we propose spatiotemporal matching at organic photoactive interfaces as a design principle for H2O2 photosynthesis. This concept integrates spatial control of charge distribution, reactant activation, and product release with temporal coordination of carrier dynamics and interfacial reactions. We discuss how supramolecular photocatalysts, conjugated polymers, and covalent organic frameworks achieve such regulation through molecular assembly, framework design, and interface engineering. This perspective provides new insights beyond conventional structure-performance relationships and establishes a predictive design strategy based on structural features, matching principles, and reaction pathways.

The highly stable carbon–carbon backbone of polystyrene (PS) leads to severe environmental accumulation. To overcome the polymer deterioration and low economic value associated with traditional mechanical recycling and pyrolysis, the molecular-level conversion of waste PS into high-value chemicals and advanced materials is recognized as a critical pathway. This review categorizes the chemical upcycling of PS into two main pathways: “Breaking the Backbone” (destructive cleavage) and “re-using the skeleton” (non-destructive editing). While systematically summarizing multi-energy-driven (e.g., thermal, photochemical, and electrical) deconstruction strategies that cleave the inert C(sp3)–C(sp3) main chain, this review also examines site-selective C(sp2)–H post-polymerization modification. By introducing functional groups onto the intact polymer skeleton, waste PS is converted into value-added materials. Preliminary life-cycle assessments (LCA) indicate that preserving the skeleton mitigates the energy penalty of complete backbone cleavage, offering a pragmatic and low-carbon route for plastics recycling.

Activating and manipulating the reaction pathway at active sites is essential for the design of Ru-based electrocatalysts. Herein, oxophilic Mo atoms were atomically dispersed in the oxygen-vacancy-enriched RuO2 lattices (Mo–RuO2-x) through molten salt treatment, in which oxygen-vacancy-shortened Ru–Mo dual sites are constructed and responsible for the improved acidic oxygen evolution reaction (OER). The Mo–RuO2–x electrocatalyst exhibits a low overpotential of 191 mV at 10 mA cm−2 for acidic OER and maintains sustained operation exceeding 500 h. More excitingly, the proton exchange membrane water electrolyzer (PEMWE) assembled with Mo–RuO2-x as the anode could survive from a 500 h operation at 1 A cm−2, with a cell voltage of 1.63 V. Experimental characterizations and theoretical calculations together evidence that the oxygen-vacancy-shortened Ru–Mo dual sites efficiently activate the oxide path mechanism (OPM), with oxophilic Mo possessing a higher d-band center than Ru, which favors the adsorption of O* intermediates and accelerates the *OO* coupling process for the improved acidic OER performance. This work demonstrates an alternative approach for the regulation of OPM at dual sites via lattice and oxophilicity engineering, which is guiding the design of Ru-based electrocatalysts toward industrial-level PEMWE.