Electro-Fenton (EF) is one of the most effective processes for treating organic pollutants in water. However, its performance is often restricted by mass transport limitations and slow catalytic reactions. While recent reviews have summarized various strategies to enhance the EF process performance, a focused analysis separating the physical magnetohydrodynamic (MHD) effect on mass transport from the quantum spin-chemistry effect on reaction kinetics-one of the most promising enhancement routes-has not yet been established. Here, this gap is addressed by developing a framework including the four key species of the EF systems: the Fe²⁺/Fe³⁺ redox couple, the reactants (H⁺ and O₂), and the electrons supplied. On this basis, the influence of magnetic fields on each species is examined, clearly distinguishing MHD-driven mass transport from spin-chemistry effects on intrinsic kinetics. This distinction helps resolve ongoing mechanistic debates and provides practical guidance for designing advanced magnetically assisted water treatment technologies.

Employing photocatalysis for water splitting to generate hydrogen (H₂) is regarded as a highly viable strategy for attaining green and efficient H₂ production. However, photocatalysis faces significant challenges in charge separation and instability. Notably, sulfide-based photocatalysts are often severely limited by photocorrosion issues. In this work, we employed a NiMoO₄/twinned Mn_0.5Cd_0.5S (NiMoO₄/T-MCS) heterojunction as a model catalyst. By modulating the alkalinity of the aqueous solution to promote rapid consumption of photogenerated holes (h⁺), the surface reaction kinetics was greatly enhanced, achieving an exceptional H₂ evolution rate (r_H2) of 28.22 mmol·g⁻¹·h⁻¹ in 4 M NaOH solution. The external NaOH facilitates the water oxidation half-reaction, preferentially consuming photogenerated h⁺ to generate ·OH radicals. This process triggers surface hydroxylation, significantly boosting both catalytic activity and stability. Furthermore, the generated ·OH radicals effectively degrade methylene blue (MB). Critically, the substantially enhanced surface reaction efficiency—particularly the rapid consumption of photogenerated h⁺—dramatically improves the system’s operational stability. This study demonstrates concurrent H₂ production and pollutant purification solely through solution modulation, alongside a significant enhancement in system efficiency.

Two-dimensional/two-dimensional (2D/2D) S-scheme heterojunctions have emerged as promising photocatalytic platforms due to their intimate face-to-face interfaces, large specific surface areas, shortened charge-migration pathways, and strong interfacial built-in electric fields. The S-scheme charge-transfer mechanism selectively recombines low-energy carriers while preserving highly reductive electrons and strongly oxidative holes, enabling efficient charge separation without compromising redox capability. This review summarizes recent progress in 2D/2D S-scheme heterojunction photocatalysts, focusing on charge-transfer mechanisms, band-alignment requirements, structural merits, and design principles. Representative construction strategies—including mixing-assisted assembly, surface chemical regulation, and in situ growth—are discussed, along with key characterization techniques for probing interfacial structures and validating S-scheme charge transfer, such as electron microscopy, X-ray photoelectron spectroscopy, Kelvin probe force microscopy, electron paramagnetic resonance, in situ irradiated XPS, transient spectroscopy, and density functional theory calculations. We further review recent modification strategies—including multidimensional heterointerface construction, interfacial bonding, elemental doping, defect engineering, cocatalyst engineering, single-atom regulation, interfacial strain and facet engineering—in terms of their effects on charge separation, redox activity, and surface reaction kinetics. Finally, applications in H₂ evolution, CO₂ reduction, pollutant degradation, and H₂O₂ production are summarized, and key challenges as well as future design directions are outlined.