Pd nanocluster-decorated CoFe composite supported on nitrogen carbon nanotubes as a high-performance trifunctional electrocatalyst

Rational design and synthesis of low-cost trifunctional electrocatalysts with improved stability and superior electrocatalytic activity for oxygen reduction reaction(ORR),oxygen evolution reaction(OER),and hydrogen evolution reaction(HER) are highly desirable but remain as the bottlenecks at the current state of technology.In this paper,the cobalt-iron(Co-Fe) composite supported on nitrogen-doped carbon nanotubes(CoFe composite/NCNTs) is synthesized.The intrinsic OER and HER catalytic activities of this CoFe composite/NCNTs composite are significantly improved with palladium(Pd) nanocluster decoration [Pd-coated(CoFe composite/NCNTs)].The as-prepared Pd-coated(CoFe composite/NCNTs) catalyst exhibits excellent trifunctional electrocatalytic activity and stability due to the interfacial coupling between Pd and(CoFe composite/NCNTs).This catalyst is successfully employed in the water electrolysis cell as both OER and HER electrode catalysts,flexible rechargeable Zn-air battery as the bifunctional ORR and OER electrode catalyst.The cell voltage of this catalyst-coated electrodes requires only 1.60 V to achieve 10 mA cm^(-2) current density for water electrolysis cell,which is comparable to and even better than that of Pt/C and Ir/C based cell.The primary Zn-air battery using this catalyst shows a constant high open-circuit voltage(OCV) of 1.47 V and a maximum power density of 261 mW cm^(-2) in the flooded mode configuration.Most importantly,a flexible Zn-air battery with this catalyst runs very smoothly without a change in voltage gap during flat,bending,and twisting positions.

Dendrite‐free lithium and sodium metal anodes with deep plating/stripping properties for lithium and sodium batteries

Although lithium(Li)and sodium(Na)metals can be selected as the promising anode materials for next‐generation rechargeable batteries of high energy density,their practical applications are greatly restricted by the uncontrollable dendrite growth.Herein,a platinum(Pt)–copper(Cu)alloycoated Cu foam(Pt–Cu foam)is prepared and then used as the substrate for Li and Na metal anodes.Owing to the ultrarough morphology with a threedimensional porous structure and the quite large surface area as well as lithiophilicity and sodiophilicity,both Li and Na dendrite growths are significantly suppressed on the substrate.Moreover,during Li plating,the lithiated Pt atoms can dissolve into Li phase,leaving a lot of microsized holes on the substrate.During Na plating,although the sodiated Pt atoms cannot dissolve into Na phase,the sodiation of Pt atoms elevates many microsized blocks above the current collector.Either the holes or the voids on the surface of Pt–Cu foam what can be extra place for deposited alkali metal,what effectively relaxes the internal stress caused by the volume exchange during Li and Na plating/stripping.Therefore,the symmetric batteries of Li@Pt–Cu foam and Na@Pt–Cu foam have both achieved long‐term cycling stability even at ultrahigh areal capacity at 20 mAh cm−2.