Phase-Dependent Synthesis of Ru Grown on TiO₂ for Solar Driven H₂ Evolution

Crystal phase engineering provides a promising strategy for enhancing photocatalytic hydrogen evolution performance, yet the precise impact of phase structure on activity requires further exploration. In this study, hcp- and fcc-phase Ru nanoparticles were synthesized via precursor and solvent-controlled reduction processes and integrated with TiO2. Photocatalytic hydrogen evolution tests reveal that hcp-Ru/TiO2 achieves the highest H2 production rate of 23.52 μmol/h, surpassing fcc-Ru/TiO2 (11.18 μmol/h) and bare TiO2 (4.72 μmol/h). Electrochemical and photophysical analyses demonstrate that hcp-Ru/TiO2 exhibits superior charge separation and transfer efficiency, as evidenced by the lowest charge transfer resistance, highest photocurrent response, and prolonged fluorescence lifetime. Theoretical calculations further confirm that hcp-Ru offers optimal hydrogen adsorption energy (ΔGH* = −0.14 eV), contributing to reduced overpotential and enhanced catalytic activity. This work underscores the critical role of Ru crystal phases in driving photocatalytic performance and provides new insights into phase engineering for sustainable energy applications.