Surface Functionalization of Ordered Mesoporous Hollow Carbon Spheres with Ru Organometallic Compounds as Supports of Low-Pt Content Nanocatalysts for Alkaline Hydrogen and Oxygen Evolution Reactions

Herein, we report a methodology that leads to the formation of Ru metallic sites, followed by the development and anchorage of Pt-Ru alloyed nanoparticles on the surface of Ordered Mesoporous Hollow Carbon Spheres (OMHCS). Along with the Ru sites, it is demonstrated that the functionalization promotes the formation of functional groups on the surface of the OMHCS. In a first stage, OMHCS are functionalized with the [(η6-C6H5OCH2CH2OH)RuCl2]2 (Ru-dim) and [(η6-C6H4CH(CH3)2CH3)RuCl2]2 (Ru-cym) organometallic compounds. Afterwards, Pt nanoparticles are dispersed by the microwave-assisted polyol method over the functionalized supports obtaining the low-metal content 5 wt. % Pt/OMHCSRu-dim and Pt/OMHCSRu-cym nanocatalysts. The degree of Ru alloyed is found to be around 35%. The low-Pt content Pt/OMHCSRu-cym and Pt/OMHCSRu-dim exhibit a higher catalytic activity for the Oxygen (OER) and the Hydrogen (HER) Evolution Reactions than the Pt/C benchmark and the Pt/OMHCS nanocatalysts. The overpotential for the OER at 10 mA cm-2 (ηOER) is 300 mV and 210 mV smaller at Pt/OMHCSRu-cym and Pt/OMHCSRu-dim compared to Pt/C, respectively. The corresponding values of the HER at -10 mA cm-2 (ηHER) are 14 and 18 mV smaller, respectively. The high catalytic activity of Pt/OMHCSRu-cym and Pt/OMHCSRu-dim has been attributed in part to the presence of Ru0 and RuO2 species from organometallic functionalization, and the modification of the d-valence band of Pt. Their high performance for the OER and the HER opens new lines of research for the design of nanocatalysts for alkaline electrochemical water splitting.