Search

Vacancy engineering is an effective strategy to manipulate the electronic structure of electrocatalysts to improve their performance, but few reports focus on phosphorus vacancies (Pv). Herein, the creation of Pv in metal phosphides and investigation of their role in alkaline electrocatalytic hydrogen evolution reaction (HER) is presented. The Pv‐modified catalyst requires a minimum onset potential of 0 mV vs. RHE, a small overpotential of 27.7 mV to achieve 10 mA cm−2 geometric current density and a Tafel slope of 30.88 mV dec−1, even outperforms the Pt/C benchmark (32.7 mV@10 mA cm−2 and 30.90 mV dec−1). This catalyst also displays superior stability up to 504 hours without any decay. Experimental analysis and density functional theory calculations suggest Pv can weaken the hybridization of Ni 3d and P 2p orbitals, enrich the electron density of Ni and P atoms nearby Pv, and facilitate H* desorption process, contributing to outstanding HER activity and facile kinetics. [ABSTRACT FROM AUTHOR]

Three kinds of Mn3O4 nanoparticles with different shapes (spheres, cubes, and ellipsoids) are selectively grown on nitrogen-doped graphene sheets through a two-step liquid-phase procedure. These non-precious hybrid materials display an excellent ORR activity and good durability. The mesoporous microstructure, nitrogen doping, and strong bonding between metal species and doped graphene are found to facilitate the ORR catalytic process. Among these three kinds of Mn3O4 particles, the ellipsoidal particles on nitrogen-doped graphene exhibit the highest ORR activity with a more positive onset-potential of -0.13 V (close to that of Pt/C, -0.09 V) and a higher kinetic limiting current density ( JK) of 11.69 mA cm-2 at -0.60 V. It is found that the ORR performance of hybrid materials can be correlated to the shape of Mn3O4 nanocrystals, and specifically to the exposed crystalline facets associated with a given shape. The shape dependence of Mn3O4 nanoparticles integrated with nitrogen-doped graphene on the ORR performance, reported here for the first time, may advance the development of fuel cells and metal-air batteries. [ABSTRACT FROM AUTHOR]

Eine hoch hydratisierte Struktur für die Katalyse der Sauerstoffentwicklungsreaktion (OER) ist durch signifikant verbesserte katalytische Aktivität, günstige Kinetik und hohe Beständigkeit gekennzeichnet. Die höhere Leistungsfähigkeit korreliert mit einem Mechanismus an zwei aktiven Zentren, und eine hohe Hydrophilie der Elektrode kann die Oxidation von Wasser zu molekularem Sauerstoff enorm beschleunigen. [ABSTRACT FROM AUTHOR]

MOFs attracted considerable attention as morphology templates and constitution precursors for synthesis of multiple functional nanocomposites due to their diverse and robust framework structure. In this work, a nickel-phosphide@carbon (Ni 2 P@C) composite with unique nanorod array morphology was synthesized via a facile phosphorization process using Ni(II)-zeolitic imidazolate framework-67 (ZIF-67-Ni) as the precursor. And the effect of phosphorization temperature on the morphology and structure of the products were carefully investigated. The products obtained under different phosphorization temperature were utilized as electrocatalysts for hydrogen evolution reaction (HER). The results showed that Ni 2 P@C nanorod array achieved under the phosphorization temperature of 400 °C demonstrated the highest electrocatalytic activity toward HER in 0.5 M sulfuric acid solution with a low overpotential of 186 mV at the current density of 10 mA cm −2 . Also, high catalytic durability and chemical stability of the Ni 2 P@C nanorod array for HER were achieved. Combing the morphology and structure characterization experiments, the reason for high HER performance of Ni 2 P@C nanorod array obtained at the phosphorization temperature of 400 °C was discussed. This work provides a new guidance for the synthesis of high-performance MOFs-derived electrocatalyst for electrochemical HER. [ABSTRACT FROM AUTHOR]