This review provides an overview of significant innovations in photocatalysts for hydrogen production, including selection criteria, modifications to enhance photocatalytic activity, and mechanisms and thermodynamics. A variety of semiconductors, such as TiO₂, g-C₃N₄, graphene-, sulfide-, oxide-, nitride-, oxysulfide-, oxynitrides, and cocatalyst-based photocatalysts, have been examined. Techniques for enhancing the compatibility of metals and nonmetals are discussed to boost photoactivity under visible light irradiation. Special attention has been given to the development of heterojunctions, including type I, type II, type III, Z-systems, and S-scheme systems. It is important to thoroughly investigate these issues in the context of visible light irradiation to enhance the efficacy of photocatalytic action. Another advancement may involve using mediators like graphene oxide and metals to establish indirect Z-scheme setups with correct band adjustment. The potential consideration of reaction chemistry, mass transfer, reaction kinetics, light diffusion restriction, and the selection of suitable light and photoreactor will optimize sustainable hydrogen output efficiency and selectivity. The review discusses the importance of photocatalysts in solar water splitting systems, such as photovoltaic electrolysis (PV-E), photocatalysis, and photoelectrochemical cells (PE-Cs). Photocatalytic systems are cheaper and have lower operational costs compared to other methods. The cost of hydrogen production depends on assumptions, particularly that future photocatalytic systems will achieve a solar-to-hydrogen conversion efficiency of up to 10%, a significant improvement compared to the approximately 1% efficiency observed in small-scale trials. The primary objective of this endeavor is to develop and build a highly efficient water-splitting technique. Photocatalytic materials must display properties needed to achieve specific applications. They require adequate band edge location, narrow energy gap band, enhanced charge separation, improved resistance to recombination, and effective interfacial interlinkages. The synthesis of materials with changeable band gap energies and band edge placement has been emphasized to generate species needed for redox and absorb the entire energy of the sun, which is the UV–vis–NIR sun spectrum. Photocatalytic water splitting is a thermodynamic process consisting of two half-reactions to generate hydrogen and oxygen, requiring +237.2 kJ/mol free energy and 1.23 V standard reduction potential. The review discusses the thermodynamic aspects of the water splitting process, including the role of electron and hole population differential, and the Gibbs energy transition. The review also covers the selection of photocatalysts for water splitting for hydrogen evolution, including titanium dioxide (TiO₂), other metal oxides, metal nitrides, metal sulfides, oxysulfides, and oxynitrides. The review highlights the importance of cocatalysts in enhancing the efficiency of hydrogen and oxygen production. The review discusses strategiesThis review provides an overview of significant innovations in photocatalysts for hydrogen production, including selection criteria, modifications to enhance photocatalytic activity, and mechanisms and thermodynamics. A variety of semiconductors, such as TiO₂, g-C₃N₄, graphene-, sulfide-, oxide-, nitride-, oxysulfide-, oxynitrides, and cocatalyst-based photocatalysts, have been examined. Techniques for enhancing the compatibility of metals and nonmetals are discussed to boost photoactivity under visible light irradiation. Special attention has been given to the development of heterojunctions, including type I, type II, type III, Z-systems, and S-scheme systems. It is important to thoroughly investigate these issues in the context of visible light irradiation to enhance the efficacy of photocatalytic action. Another advancement may involve using mediators like graphene oxide and metals to establish indirect Z-scheme setups with correct band adjustment. The potential consideration of reaction chemistry, mass transfer, reaction kinetics, light diffusion restriction, and the selection of suitable light and photoreactor will optimize sustainable hydrogen output efficiency and selectivity. The review discusses the importance of photocatalysts in solar water splitting systems, such as photovoltaic electrolysis (PV-E), photocatalysis, and photoelectrochemical cells (PE-Cs). Photocatalytic systems are cheaper and have lower operational costs compared to other methods. The cost of hydrogen production depends on assumptions, particularly that future photocatalytic systems will achieve a solar-to-hydrogen conversion efficiency of up to 10%, a significant improvement compared to the approximately 1% efficiency observed in small-scale trials. The primary objective of this endeavor is to develop and build a highly efficient water-splitting technique. Photocatalytic materials must display properties needed to achieve specific applications. They require adequate band edge location, narrow energy gap band, enhanced charge separation, improved resistance to recombination, and effective interfacial interlinkages. The synthesis of materials with changeable band gap energies and band edge placement has been emphasized to generate species needed for redox and absorb the entire energy of the sun, which is the UV–vis–NIR sun spectrum. Photocatalytic water splitting is a thermodynamic process consisting of two half-reactions to generate hydrogen and oxygen, requiring +237.2 kJ/mol free energy and 1.23 V standard reduction potential. The review discusses the thermodynamic aspects of the water splitting process, including the role of electron and hole population differential, and the Gibbs energy transition. The review also covers the selection of photocatalysts for water splitting for hydrogen evolution, including titanium dioxide (TiO₂), other metal oxides, metal nitrides, metal sulfides, oxysulfides, and oxynitrides. The review highlights the importance of cocatalysts in enhancing the efficiency of hydrogen and oxygen production. The review discusses strategies