RESUMEN
Ligand effect, induced by charge transfer between catalytic surface and substrate in core/shell structure, was widely proved to benefit Pt-catalyzed oxygen reduction reaction by tuning the position of d-band center of Pt theoretically. However, ligand effect is always convoluted by strain effect in real core/shell nanostructure; therefore, it remains experimentally unknown whether and how much the ligand effect solely contributes electrocatalytic activity improvements. Herein, we report precise synthesis of a kind of Pd3Ru1/Pt core/shell nanoplates with exclusive ligand effect for oxygen reduction reaction. Layer-by-layer growth of Pt overlayers onto Pd3Ru1 nanoplates can guarantee no lattice mismatch between core and shell because the well-designed Pd3Ru1 has the same lattice parameters as Pt. Electron transfer, due to the exclusive ligand effect, from Pd3Ru1 to Pt leads to a downshift of d-band center of Pt. The optimal Pd3Ru1/Pt1-2L nanoplates achieve excellent activity and stability for oxygen reduction reaction in alkaline/acid electrolyte.
RESUMEN
Zinc-air batteries (ZABs) are regarded as attractive devices for electrochemical energy storage and conversion due to their outstanding electrochemical performance, low price, and high safety. However, it remains a challenge to design a stable and efficient bifunctional oxygen catalyst that can accelerate the reaction kinetics and improve the performance of ZABs. Herein, a phosphorus-doped transition metal selenide/carbon composite catalyst derived from metal-organic frameworks (P-CoSe2/C@CC) is constructed by a self-supporting carbon cloth structure through a simple solvothermal process with subsequent selenization and phosphatization. The P-CoSe2/C@CC exhibits a low overpotential of 303.1 mV at 10 mA cm-2 toward the oxygen evolution reaction and an obvious reduction peak for the oxygen reduction reaction. The abovementioned electrochemical performances for the P-CoSe2/C@CC are attributed to the specific architecture, the super-hydrophilic surface, and the P-doping effect. Remarkably, the homemade zinc-air battery based on our P-CoSe2/C@CC catalyst shows an expected peak power density of 124.4 mW cm-2 along with excellent cycling stability, confirming its great potential application in ZABs for advanced bifunctional electrocatalysis.
RESUMEN
Metal organic frameworks (MOFs) have been considered as one of the most promising electrode materials for electrochemical capacitors due to their large specific surface area and abundant pore structure. Herein, we report a Co-MOF electrode with a vertical-standing 2D parallelogram-like nanoarray structure on a Ni foam substrate via a one-step solvothermal method. The as-prepared Co-MOF on a Ni foam electrode delivered a high area-specific capacitance of 582.0 mC cm-2 at a current density of 2 mA cm-2 and a good performance rate of 350.0 mC cm-2 at 50 mA cm-2. Moreover, an asymmetric electrochemical capacitor (AEC) device (Co-MOF on Ni foam//AC) was assembled by using the as-prepared Co-MOF on a Ni foam as the cathode and a active carbon-coated Ni foam as the anode to achieve a maximum energy density of 0.082 mW cm-2 at a power density of 0.8 mW cm-2, which still maintained 0.065 mW cm-2 at a high power density of 11.94 mW cm-2. Meanwhile, our assembled device exhibited an excellent cycling stability with a capacitance retention of nearly 100% after 1000 cycles. Therefore, this work provides a simple method to prepare MOF-based material for the application of energy storage and conversion.
