Search

• MP-MOx has efficient activity for H 2 generation and organic molecules oxidation • MP-MOx exhibits remarkable anti-toxicity for organic molecules • As compared with water electrolysis the organic electrolysis is more efficient • This strategy can combine H 2 generation with sewage disposal Replacing the bootless and sluggish oxygen evolution reaction with the oxidation of some more readily oxidized chemical products is a feasible strategy for energy-saving H 2 generation. However, its broad application is inhibited by the costly raw materials, noble-metal catalysts and the toxic effect of organic molecules on catalysts. Herein, we report a novel anti-poisoning MP-MOx (M = Ni, Fe and Mo) bifunctional catalyst that can combine the energy-saving H 2 production with sewage disposal simultaneously by directly electrolyzing the wastewater containing organic molecules. The MP-MOx catalyst expresses a commendable electrocatalytic activity for hydrogen evolution reaction and electrooxidation decomposition of small organic molecules (EDM), as well as a remarkable anti-toxicity for organic molecules and a long-term durability. As compared with traditional water electrolysis, the organic electrolytic system exhibits an excellent cell efficient with a cell voltage reducing of 120 mV and can dramatically allow electrical energy savings up to 8% at 10 mA cm−2. [ABSTRACT FROM AUTHOR]

Metal-nitrogen doped carbon catalysts (M-N/C) with abundantly accessible M-N x sites, particularly single metal atom M-N/C (SAM-N/C), have been developed as a substitute for expensive Pt-based catalysts. These catalysts are used to increase the efficiency of otherwise sluggish oxygen reduction reactions (ORR) and hydrogen evolution reactions (HER). However, although the agglomerated metal nanoparticles are usually easy to form, they are very difficult to remove due to the protective surface-coating carbon layers, a factor that significantly hampers SAM-N/C fabrication. Herein, we report a one-step pyrolysis approach to successfully fabricate single cobalt atom Co-N/C (SACo-N/C) by using a Co2+-SCN- coordination compound as the metal precursor. Thanks to the decomposition of Co2+-SCN- compound at lower temperature than that of carbon layer deposition, Co-rich particles grow up to larger ones before carbon layers formation. Even though encapsulated by the carbon layers, it is difficult for the large Co-rich particle to be completely sealed. And thus, it makes the Co atoms possible to escape from incomplete carbon layer, to coordinate with nitrogen atoms, and to form SACo-N/C catalysts. This SACo-N/C exhibits excellent performances for both ORR (half-wave potential of 0.878 V) and HER (overpotential at 10 mA/cm2 of 178 mV), and is thus a potential replacement for Pt-based catalysts. When SACo-N/C is integrated into a Zn-O 2 battery, battery with high open-circuit voltage (1.536 V) has high peak power density (266 mW/cm2) and large gravimetric energy density (755 mA h/g Zn) at current densities of 100 mA/cm2. Thus, we believe that this strategy may offer a new direction for the effective generation of SAM-N/C catalysts. [ABSTRACT FROM AUTHOR]

Developing efficient electrocatalysts is extremely desirable to decrease the overall cost of electrochemical devices. It usually lies in interface modification for improving intrinsic activity of active sites, and structural optimization for facilitating mass transport. Herein, we rationally design a series of carbon-based hierarchical architectures as bifunctional electrocatalysts through control pyrolysis of metal−organic frameworks coated layered double hydroxide nanoplatelets. Three kinds of catalysts with hierarchical structures are produced, nanoparticles dispersed on carbonized metal oxide nanosheets, carbon nanotubes vertically grown on carbonized metal oxide nanosheets, and carbon nanosheets vertically grown on carbonized metal oxide nanosheets. Among them, the carbon nanotubes vertically grown on carbonized metal oxide nanosheets electrocatalyst possesses the highest electrochemical surface area, lowest charge-transfer resistance, and the fast mass transfer rate, owing to its unique hierarchical porous structure. These properties lead to excellent catalytic activities for oxygen reduction/evolution reactions in terms of half-wave potential (835 mV) and low overpotential (280 mV), which make it a significant electrocatalyst for zinc-air batteries with respectable discharge-charge performance, peak power density (235 mW cm−2), specific capacitance (875 mAh g−1) and better stability than precious metal catalysts. Image 1 • Nano-engineering of hierarchical architectures through controlled pyrolysis. • Highly modest and fast route for synthesizing bifunctional electrocatalyst. • The superior activity ascribed to the growth of carbon nanotubes on 2D nanosheets. • Better catalytic performance than high cost precious electrocatalysts. [ABSTRACT FROM AUTHOR]