Exploring sustainable and efficient electrocatalysts for oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) is necessary for the development of fuel cells and metal-air batteries. Herein, we report a bimetal Fe/Mn-N-C material composed of spinel MnFeO/metallic Fe hybrid nanoparticles encapsulated in N-doped mesoporous hollow carbon nanospheres as an excellent bifunctional ORR/OER electrocatalyst in alkaline electrolyte. The Fe/Mn-N-C catalyst is synthesized via pyrolysis of bimetal ion-incorporated polydopamine nanospheres and shows impressive ORR electrocatalytic activity superior to Pt/C and good OER activity close to RuO catalyst in alkaline environment. When tested in Zn-air battery, the Fe/Mn-N-C catalyst demonstrates excellent ultimate performance including power density, durability, and cycling. This work reports the bimetal Fe/Mn-N-C as a highly efficient bifunctional electrocatalyst and may afford useful insights into the design of sustainable transition-metal-based high-performance electrocatalysts.
The outstanding electrocatalytic activityo f ruthenium (Ru) phosphides towardt he hydrogen evolution reaction( HER) has received wide attention.H owever, the effect of the Ru phosphide phase on the HER performance remains unclear.H erein, at wo-step methodw as developed to synthesize nanoparticles of three types of Ru phosphides, namely,R u 2 P, RuP,a nd RuP 2 ,w ith similar morphology,d imensions,l oading density,a nd electrochemical surface area on graphene nanosheets by simply controlling the dosageo fp hytic acida sPsource. Electrochemical tests revealed that Ru 2 P/graphene shows the highesti ntrinsic HER activity,f ollowedb yR uP/graphene and RuP 2 /graphene. Ru 2 P/graphene affords ac urrent density of 10 mA cm À2 at an overpotential of 18 mV in acid media.T heoretical calculationsf urthers howed that P-deficient Ru 2 Phas alower free energy of hydrogena dsorption on the surface than other two, P-rich Ru phosphides (RuP, RuP 2 ), which confirms the excellent intrinsic HER activity of Ru 2 Pa nd is consistent with experiment results. The work reveals for the first time ac lear trend of HER activity among three Ru phosphide phases.[a] T.
The spatially resolved electrochemical reversibility of a polyaniline (PANI) thin film is successfully imaged by an oblique-incidence reflectivity difference (OIRD) technique.
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