Coupling photocatalytic H₂ evolution and phenol degradation have drawn much attention on H₂ as clean energy and phenol as an organic pollutant to the environment. Such dual-function reaction can utilize the chemical potential of phenol oxidation to make up the chemical potential required for hydrogen evolution from water splitting. The production of H₂ thus was enhanced via the phenol oxidation. However, H₂ is still needed to be purified from the reaction products by traditional methods. In this study, we demonstrated the simultaneous separation of H₂ using a photo twin-reactor under artificial sunlight, in which the photocatalytic efficiency was substantially increased due to the inhibition of backward reaction by separating H₂ from the products directly. Three Rh-doped SrTiO₃ (STO) photocatalysts calcined at 900, 1100, 1200 °C (named as STO:Rh900, STO:Rh1100, and STO:Rh1200, respectively) were prepared by solid-state fusion reaction, then photo-deposition method was applied to synthesize Pt loading STO:Rh. All photocatalysts were fully characterized by XRD, XPS, UV–vis, SEM, TEM, and DLS. A single reactor and a twin-reactor (Z-scheme system) were systematically designed by using Pt/STO:Rh for H₂ evolution photocatalyst and WO₃ for phenol oxidation photocatalyst, where Fe³⁺/Fe²⁺ pairs were served as electron transfer mediators to conduct the dual-function reaction. In the single reactor, the stoichiometric of the dual-function reaction was proposed and with high consistency to the experimental data. By using the twin-reactor, H₂ production rate increased 2.7 times, reaching 1.90 μmol g⁻¹ h⁻¹, compared to that in the single reactor. Moreover, the H₂ concentration of the gas-phase products increased from 70% (in the single reactor) to 94% owing to the separation function of the twin-reactor, which would significantly reduce the cost for further purification. The effect of phenol concentration on H₂ production in the twin-reactor was also thoroughly investigated. The results showed that increased phenol initial concentration would enhance the production of H₂. With 200 μmol L⁻¹ phenol, the H₂ yield (11.37 μmol g⁻¹ in 6-h reaction) was increased by 20% compared to that of pure water splitting.