Phase-Controlled Synthesis of Ru Supported on Carbon Nitride and the Application in Photocatalytic H2 Evolution

This work aims to explore the influence of crystal phase engineering on the photocatalytic hydrogen evolution activity of Ru/C3N4 systems. By precisely tuning the combination of Ru precursors and reducing solvents, we successfully synthesized Ru co-catalysts with distinct crystal phases (hcp and fcc) and integrated them with C3N4. The photocatalytic hydrogen evolution experiments demonstrated that hcp-Ru/C3N4 achieved a significantly higher hydrogen evolution rate (24.23 μmol h−1) compared to fcc-Ru/C3N4 (7.44 μmol h−1), with activity reaching approximately 42% of Pt/C3N4 under the same conditions. Photocurrent and electrochemical impedance spectroscopy analyses revealed that hcp-Ru/C3N4 exhibited superior charge separation and transfer efficiency. Moreover, Gibbs free energy calculations indicated that the hydrogen adsorption energy of hcp-Ru (ΔGH* = −0.14 eV) was closer to optimal compared to fcc-Ru (−0.32 eV), enhancing the hydrogen generation process. These findings highlight that crystal-phase engineering plays a critical role in tuning the electronic structure and catalytic properties of Ru-based systems, offering insights for the design of highly efficient noble metal catalysts for photocatalysis.