Nitrogen-Containing-Defect-Site-Assisted H₂O Adsorption and Dissociation on Crystalline Ru Nanoclusters by Quasi-Hydrogen Bonds Boosts Alkaline Hydrogen Evolution Reaction

Abstract

In the pursuit of advancing electrolytic water hydrogen production technology, the development of a costeffective alkaline hydrogen evolution reaction (HER) catalyst, characterized by high activity and stability, holds paramount importance. In this context, we synthesized a crystalline Ru nanoclusters (NCs) catalyst supported on a three-dimensional layered nitrogen-doped carbon (3DLNC) material through a straightforward impregnation pyrolysis method. The optimized Ru/3DLNC-500 catalyst demonstrated remarkable electrocatalytic performance, featuring an exceptionally low overpotential of 18.5 mV at 10 mA cm −2 , an extraordinarily high mass activity (10-fold greater than a 20% platinum carbon catalyst), and commendable stability. Insights gained from in situ Raman characterization and theoretical calculations lead to two noteworthy conclusions. First, the alkaline HER activity of crystalline Ru NCs is attributed to their heightened water adsorption capacity and accelerated hydrogen desorption rate. Second, under reaction conditions, the nitrogen-containing defect sites on the surface of 3DLNC serve as additional sites for water molecule adsorption by forming quasihydrogen bonds, thereby facilitating the alkaline HER by enhancing the adsorption and dissociation capabilities of water molecules on the catalyst.

Highly Dispersed Quasi-1 nm Ruthenium Nanoclusters on Hierarchical Nitrogen-Doped Carbon Nanocages Constructed by Surface-Constrained Sintering for Alkaline Hydrogen Evolution

“…To regulate the electronic structure of Ru-based catalysts and thus optimize the *H adsorption/desorption energy, many strategies have been developed, such as morphology/size control, alloying with other metals, heteroatoms-doping, and support engineering. − Downsizing the Ru species from nanoparticles (>2 nm) to nanoclusters (0.2–2 nm) and even single-sites (<0.2 nm) can not only greatly change the electronic structure but also substantially increase the atom utilization. , Among them, the Ru–N x single-sites are favorable for the *H adsorption/desorption but unfavorable for the H 2 O dissociation due to the absence of adjacent sites, usually resulting in the inferior HER performances in alkaline/neutral electrolytes. , In contrast, the Ru nanoclusters can achieve the “win-win” goal of electronic structure regulation and high active sites for H 2 O dissociation, suggesting the great potential in the alkaline HER. , The small-sized Ru nanoclusters usually mean easy agglomeration due to their high surface energy; hence, support engineering is necessary to immobilize Ru nanoclusters by improving the metal–support interaction. ,− The 3D N-doped carbon supports have shown great promise in the construction of noble metal catalysts since their 3D hierarchical porous structure and high conductivity can facilitate the charge/mass synergic transport and the high utilization of metal active species. , In recent years, our group has developed a unique support of hierarchical carbon-based nanocages with combined merits of large specific surface area (SSA), high conductivity, coexisting micromeso-macropores, and easy heteroatoms doping, becoming a multifunctional platform for energy storage and conversion. − Moreover, the abundant micropores and N-dopants on the surface can easily capture metal species and regulate the metal–support interaction, showing great promise to construct highly active and stable catalysts. , Herein, by taking the hierarchical N-doped carbon nanocages (hNCNC) as support, highly dispersed Ru nanoclusters are constructed by a simple adsorption-annealing process governed by surface-constrained sintering, which present a quasi-1 nm size and strong metal–support interaction due to the anchoring effect of N dopants. The optimized electrocatalyst exhibits the ultralow overpotential of 21 mV at 10 mA cm –2 and excellent stability in 1 M KOH, superior to the Pt/C benchmark.…”