Ultra-small RuO₂/NHC nanocrystal electrocatalysts with efficient water oxidation activities in acidic media

Abstract

Designing highly active and durable oxygen evolution reaction (OER) electrocatalysts is indispensable for promoting the sluggish reaction kinetics of OER to achieve low overpotential. RuO2 is one of the representative...

Morphological and Coordination Modulations in Iridium Electrocatalyst for Robust and Stable Acidic OER Catalysis

“…[57] The physical properties of this class of materials (high specific surface area) provide not only more active species but also significant tunability in surface oxidation states and hybridization, which provide excellent opportunities to solve the large overpotential problem described above. [58] Therefore, it is crucial to design and develop some universal methods that can synthesize twodimensional (2D) Ir-based electrocatalysts in large quantities to reduce diffusion detours and increase accessibility of active sites, two theoretical approaches (liberating more active sites together with tuning the external electronic structure of the active site) are commonly applied to promote the catalytic activity. [59] However, metal Ir nanosheet structures under ordinary conditions are rarely reported because high surface energy is not favourable for the assembly of 2D nanosheets; harsh conditions (such as high temperature, high pressure) are required to complete some noble metal nanosheets.…”

Recent Progress in Ruthenium-Based Electrocatalysts for Water Oxidation under Acidic Condition

“…This strategy is highly effective to modulate the active sites for catalytic reactions. For example, Liu et al loaded ultrasmall RuO 2 nanocrystals (∼3.5 nm) on N-doped hierarchical porous carbon (NHC) with a high surface area, which exposed more active sites and introduced oxygen vacancies, resulting in a comprehensive improvement in its OER activity in acid . The optimized RuO 2 /NHC catalyst required a low overpotential of 186 mV to acquire the current density of 10 mA cm –2 and exhibited a Tafel slope of 60 mV dec –1 for OER in 0.5 M H 2 SO 4 .…”

“…Coupling RuO 2 with other phases effectively enhances its OER performance in acid. For example, the composites with different metals, ,− metal oxides, ,− nonmetals, ,,, or carbide have been reported. For instance, Yang et al modulated the charge density of RuO 2 in Ru@RuO 2 core–shell nanoparticles (Ru@RuO 2 -L) synthesized by a one-step laser irradiation method for OER in acid .…”

“…For example, Liu et al loaded ultrasmall RuO 2 nanocrystals (∼3.5 nm) on N-doped hierarchical porous carbon (NHC) with a high surface area, which exposed more active sites and introduced oxygen vacancies, resulting in a comprehensive improvement in its OER activity in acid. 100 The optimized RuO 2 /NHC catalyst required a low overpotential of 186 mV to acquire the current density of 10 mA cm −2 and exhibited a Tafel slope of 60 mV dec −1 for OER in 0.5 M H 2 SO 4 . For the RuO 2 nanosheets synthesized by exfoliation of proton exchanged NaRuO 2 , DFT calculations revealed that the terminal O cus species at the under coordinated Ru cus edge atoms were the active sites for OER (Figure 5e), 101 which is different from the general concept that transitional metal acts the active sites (Table 1).…”