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• 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]

• P123@SrTiO 3 shows high efficiency of photocatalytic hydrogen reduction performance, which is 31 times of SrTiO 3. • The P123@SrTiO 3 heterojunction was synthesized by one-step solvothermal method. • The hydrophilic heterojunction greatly improves the surface conductivity and inhibits the recombination of photogenerated carriers. Surface modification is a key strategy for promoting the photocatalytic performance of nanoparticles. In this work, triblock copolymer P123 (PEO-PPO-PEO) has been used as a surfactant in the synthesis of SrTiO 3. Instead of removing P123 by annealing after the synthesis process, the photocatalytic performance of P123@SrTiO 3 heterostructures was evaluated. Compared with SrTiO 3 , the hydrophilicity of P123@SrTiO 3 has been greatly improved. Poly ethylene oxide and its copolymers have excellent affinity for carriers and contribute to carriers transfer. At the same time, the improvement of surface wettability is beneficial to reduce the adsorption energy of water molecules, which speeds up the frequency at which carriers react with water molecules. As a result, photocatalytic hydrogen production of P123@SrTiO 3 reaches as high as 402 μmol·g−1·h−1 in the absence of any cocatalyst, which is 31 times that of pure SrTiO 3. However, the specific surface area of P123@SrTiO 3 is only 5.2 times that of SrTiO 3. P123@SrTiO 3 retained high catalytic activity after a long reaction. The construction of surface hydrophilic heterojunction provides a new idea for the design of photocatalytic materials. [ABSTRACT FROM AUTHOR]