Translate the following into Chinese: Pioneer work as early as 1972 by Fujishima and Honda reported water splitting for H 2 production over TiO 2 semiconductor. Since then, various types of semiconductors for photocatalytic H 2 productions are under investigation. Among all, titanium dioxide (TiO 2 ) with band gap 3.2eV is a recognized photocatalyst and it has been extensively studied because of numerous advantages such as low cost, high photochemical stability and non-toxic. On the other hand, wide band gap limits its applications under visible light and faster charges recombination rate lowers its photocatalytic activity. Coupling TiO 2 with visible light semiconductors can narrowing the band gap with faster charges separation, thus could enables enhanced photo-catalytic activity. Among the low band gap semiconductors, polymeric graphitic carbon nitride (g-C 3 N 4 ) has attracted more attentions as metal-free polymeric semiconductor in photocatalytic water splitting. It is a visible light responsive with lower band gap and low cost semiconductor. It can be synthesized from cheap precursors such as melamine and urea by simple thermal approach. In addition, g-C 3 N 4 has numerous advantages such as high thermal and chemical stability and appropriate band structure (2.7eV) to absorb visible light irradiation. Among the limitations, g-C 3 N 4 has low surface area and small active sites for interfacial (photon) reaction, moderate oxidation reaction of water to H + and low charge mobility which disrupt the delocalization of electrons. Hence, the coupling or/and doping g-C 3 N 4 with other elements can overcome its limitations. Among the other alternatives, coupling g-C 3 N 4 with TiO 2 to develop type II heterojunction could be promising to get enhanced H 2 production during photocatalytic water splitting under visible light irradiations. Herein, an overview and recent developments in semiconductor materials, thermodynamics and engineering approach to maximize photocatalytic water splitting for H 2 production has been discussed. First, the fundamentals and thermodynamics of photocatalysis are briefly explained. Second, the strategies to improve the photocatalytic activity by the design of TiO 2 and g-C 3 N 4 structures, morphological impacts, modification with different materials and formations of heterojunctions are summarized. The various factors that affect photocatalytic water splitting such as band gap, morphology, temperature, light intensity, pH, oxygen vacancies, and sacrificial reagents are then critically discussed. Additionally, the technology in photoreactors and the recommendation to improve the H 2 production are also explained.