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 (${r}_{{H}_{2}}$ ) 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 provide an effective route to combining efficient charge separation with strong redox capability in photocatalysis. Their planar interfaces shorten carrier transport distances, strengthen interfacial coupling, and facilitate the formation of internal electric fields. Meanwhile, the S-scheme pathway promotes the recombination of low-energy carriers while preserving highly reductive electrons and strongly oxidative holes. This review summarizes recent advances in 2D/2D S-scheme photocatalysts, emphasizing band alignment, interfacial charge transfer, structural advantages, and material selection. Major construction routes, including mixing-assisted assembly, surface chemical regulation, and in-situ growth, are compared in terms of interface formation and coupling strength. The discussion then examines how microscopy, spectroscopy, surface potential mapping, transient spectroscopy, and theoretical calculations resolve interfacial structures and verify charge transfer pathways. Recent advances in interfacial bonding, multidimensional coupling, doping, defect engineering, cocatalyst integration, single atom engineering, strain modulation, and facet control are further assessed for their effects on carrier dynamics, redox activity, and surface reaction kinetics. Finally, representative applications in H₂ evolution, CO₂ reduction, pollutant degradation, and H₂O₂ production are surveyed, and the review concludes by identifying key challenges and outlining future priorities for rational interface design.

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.