In order to facilitate the large-scale applications of rechargeable Zn-air batteries, non-noble-metal based materials with high activity for oxygen reduction (ORR) and evolution reactions (OER) are highly needed for replacing noble-metal based materials. Here, a new method is used for developing Cu-doped ZIF-67 (Cu/ZIF-67) nanoparticles and carbonizing at various temperatures (500-900°C). Benefiting from the doping of Cu nanoparticles on the surface of the ZIF-67 and the synergistic interaction between Cu and the underlying Co atoms, the Cu/Co-NC-800 electrocatalyst exhibits superior electrocatalytic activity for both ORR (Eo 0.98, E1/2 0.84 V) and OER (overpotential 0.278 V) and superior alkaline media stability relative to both prepared and commercial Pt/C (Eo 0.96 V). These insightful findings inspire new perspectives for economical-practical bifunctional oxygen electrocatalysts to be designed and synthesized rationally.
Using unsupported catalysts also improved stability during electrochemical reactions and high durability due to their non-corrosive component, Carbon. Advanced mesoporous architectures were created in which the pore and metal composition are controlled at the nanoscale level. Rigid template-assisted synthesis, which makes periodic porosity in the solid, are used to create mesoporous platinum and platinum bimetallic catalyst. The ability to control the composition, shape, and porous architecture of Pt and Pt bimetallic combinations, eliminating the carbon corrosion problem, improved the activity of the catalyst. Hence, 3D bicontinuous mesoporous silica KIT-6 and 2D mesoporous silica SBA-15 were synthesized. Ordered mesoporous silica prepared has uniform mesopores (7.9 and 7.3nm for KIT-6 and SBA-15, respectively) and high specific surface areas 772 m2.g-1 (for KIT-6) and 943 m2.g-1 (for SBA-15). These rigid silica templates were employed to produce mesoporous metal particles for fuel cell electrocatalyst.
Metal-organic frameworks (MOFs) are a type of porous material that offers a highly flexible medium for future broad application due to their crystallinity, structural diversity, and permanent porosity. Herein, by doping copper with Isoreticular metal-organic framework-3 (IRMOF-3) as a precursor, an effective electrocatalyst with x%Cu/IRMOF-3 (x = 1-10 %) porous carbon spheres were prepared and characterized. The oxygen evolution reaction (OER) electrocatalytic properties of x%Cu/IRMOF-3 were investigated. According to the findings, 5%Cu/IRMOF-3-900 has a superior performance with a low overpotential of 265 mV and strong long-term stability in alkaline solution. With a porous structure and high nitrogen content, 5%Cu doped IRMOF-3 is superior to several reported precious metal-free electrocatalysts developed of MOFs. In this research, MOF has been utilized as a template to design a new approach for developing non-noble metal OER catalysts.
The fuel cell is one of the most environmentally friendly methods for sustainably converting chemical energy to electricity. The broad use of the oxygen reduction reaction (ORR) at the cathode has been hindered up until this point by the pricy platinum catalysts required. The amount of noble metal needed for the requisite catalytic effect may be reduced using nonprecious-metal catalysts. Still, they are either too expensive for the commercial mass production of clean energy, or their energy-conversion efficiency is too low. The cheap cost, broad surface area, high electrical conductivity, abundant electrocatalytic active sites, and corrosion-resistant features have led to a new class of carbon-based, metal-free catalysts. These catalysts might significantly reduce the price and increase the effectiveness of fuel cells when utilized as substitute ORR catalysts. This review article describes several metal-free carbon-based catalysts that have been developed employing very complex designs and rational heteroatom doping (by intrinsic and macroscopic tuning).
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