Highly exposed ruthenium-based electrocatalysts from bimetallic metal-organic frameworks for overall water splitting

Highlights: • Bimetallic MOF enables low amount of Ru usage and hierarchically porous structure. • Highly exposed active sites contribute to ultrahigh HER activity in alkaline solution. • Ru-based catalyst exhibits an extremely low HER overpotential of 22.7 mV at 25 mA cm⁻². -- Abstract: The development of highly exposed active sites and highly active inexpensive electrocatalysts is important and challengeable for electrocatalytic hydrogen evolution reaction (HER). Herein, we report a bimetallic metal-organic frameworks based strategy to fabricate Ru-based electrocatalysts with high exposure of the Ru active sites (Ru-HPC, ruthenium-decorated hierarchically porous carbon) for high efficient hydrogen evolution. Remarkably, Ru-HPC achieves a current density of 25 mA cm_geo⁻² at an overpotential of 22.7 mV, and shows an ultrahigh turnover frequency of 1.79 H₂ s⁻¹ at 25 mV, which is almost twice higher than that of commercial Pt/C. The electrochemical HER performance of Ru-HPC surpasses most of the electrocatalysts reported so far in alkaline solutions. Besides, a two-electrode water splitting device is constructed with Ru-HPC and porous RuO₂ (obtained by oxidizing Ru-HPC) as electrode materials, which achieves a current density of 10 mA cm⁻² at only 1.53 V. This work provides a facile strategy to fabricate high-performance metal-carbon hybrid electrocatalysts with abundant exposed active sites from bimetallic MOFs, which can hopefully be applied to many other metals-carbon hybrids for various electrochemical applications in the foreseeable future.