Search

• NiCo 2 O 4 nano-flakes with different dopant concentrations of Ruthenium (NiCo 2-x Ru x O 4) are synthesized. • Ru dopant changes the valance state of Co, and adjust the ratio of Co2+/Co3+. • The free energy of the potential-determining step is reduced. • The optimized Ru-doped NiCo 2 O 4 exhibits excellent OER activities and smaller charge transfer resistance. Spinel oxide has a unique open structure, the existence of numerous empty interstitial sites is conducive to cation migration, so the valence of transition metal in spinel oxide is modifiable. Optimizing the valence state on the spinel surface has always been the focus of research because it is key for realizing efficient oxygen evolution reaction. In this paper, we introduced metal Ru into spinel oxide NiCo 2 O 4 to adjust the valence state of the cations on the spinel surface, achieving a suitable ion ratio of Co2+/Co3+. The catalytic performance is the best when the doping concentration of Ru is 5.7% (NiCo 1.7 Ru 0.3 O 4). In 1.0 M KOH, NiCo 1.7 Ru 0.3 O 4 required only 280 mV overpotential to drive the current of 10 mA·cm−2. The incorporation of Ru induces more Co2+ on the octahedral site and changes the valence state of Co, optimizing the adsorption of the oxygen intermediate. In addition, the coordinated charge transfer between Ru, Co, and Ni will also accelerate the reaction. These results confirm that the Ru doping process can not only change the electrochemical performance of spinel oxides but also provide new insights into the design of OER (Oxygen evolution reaction) catalysts. [ABSTRACT FROM AUTHOR]

[Display omitted] • A RuSe 2 /MoSe 2 heterostructure was prepared for HER in alkaline media. • RuSe 2 nanoparticles was uniformly dispersed onto MoSe 2 rods. • The charge redistribution over interface of RuSe 2 /MoSe 2 facilitated charge transfer. • The RuSe 2 /MoSe 2 heterostructure exhibited good performance for HER in alkaline media. • DFT was performed to investigate the mechanism behind performance improvement. Despite being regarded as a favorable substitute for platinum-based catalysts in hydrogen evolution reaction (HER), molybdenum diselenide (MoSe 2) exhibits inferior electrocatalytic performance due to its inadequate conductivity and limited active sites. However, employing molecular engineering for modification holds great potential in significantly enhancing its performance, yet it still poses significant challenges. Herein, an interface engineering strategy was adopted to obtain RuSe 2 modified MoSe 2 composite catalysts (RuSe 2 /MoSe 2). In alkaline media, RuSe 2 /MoSe 2 exhibited a reduced overpotential of 147.8 mV at 10 mA cm−2 comparing with pristine MoSe 2 (351.8 mV). Experimental findings and density functional theory (DFT) calculations indicated that increased conductivity, enhanced hydrophily and optimized adsorption free energies of hydrogen contribute to its enhanced HER activity. This work opens up an interface engineering strategy for designing more efficient selenide-based electrocatalysts. [ABSTRACT FROM AUTHOR]