Electro-triggered Joule heating method to synthesize single-phase CuNi nano-alloy catalyst for efficient electrocatalytic nitrate reduction toward ammonia

Electrochemical nitrate reduction reaction(NO_(3)RR)has great potential for ammonia(NH_(3))synthesis benefiting from its environmental friendliness and sustainability.Cu-based alloys with elemental diversity and adsorption tunability are widely used as electrocatalyst to lower the reaction overpotential for NO_(3)RR catalysis.However,phase separation commonly found in alloys leads to uneven distribution of elements,which limits the possibility of further optimizing the catalytic activity.Herein,an electrotriggered Joule heating method,possessing unique superiority of flash heating and cooling that lead to well-dispersed nanoparticles and uniform mixing of various elements,was adopted to synthesize a single-phase CuNi nano-alloy catalyst evenly dispersed on carbon fiber paper,CFP-Cu_(1)Ni_(1),which exhibited a more positive NO_(3)RR initial potential of 0.1 V versus reversible hydrogen electrode(vs.RHE)than that of pure copper nanoparticles at 10 mA·cm^(−2)in 0.5 mol·L^(−1)Na_(2)SO_(4)+0.1 mol·L^(−1)KNO_(3)solution.Importantly,CFP-Cu_(1)Ni_(1) presented high electrocatalytic activity with a Faradaic efficiency of 95.7%and NH_(3)yield rate of 180.58μmol·h^(−1)·cm^(−2)(2550μmol·h^(−1)·mg_(cat)^(−1))at−0.22 V vs.RHE.Theoretical calculations showed that alloying Cu with Ni into single-phase caused an upshift of its d-band center,which promoted the adsorption of NO_(3)−and weakened the adsorption of NH_(3).Moreover,the competitive adsorption of hydrogen ions was restrained until−0.24 V.This work offers a rational design concept with clear guidance for rapid synthesis of uniformly dispersed single-phase nano-alloy catalyst for efficient electrochemical NO_(3)RR toward ammonia.

MOF-mediated synthesis of novel PtFeCoNiMn high-entropy nanoalloy as bifunctional oxygen electrocatalysts for zinc-air battery

High-entropy alloy(HEA)-based materials are expected to be promising oxygen electrocatalysts due to their exceptional properties.The electronic structure regulation of HEAs plays a pivotal role in enhancing their elctrocatalytic ability.Herein,PtFeCoNiMn nanoparticles(NPs)with subtle lattice distortions are constructed on metal-organic framework-derived nitrogen-doped carbon by an ultra-rapid Joule heating process.Thanks to the modulated electronic structure and the inherent cocktail effect of HEAs,the as-synthesized PtFeCoNiMn/NC exhibits superior bifunctional electrocatalytic performance with a positive half-wave potential of 0.863 V vs.reversible hydrogen electrode(RHE)for oxygen reduction reaction and a low overpotential of 357 mV at 10 mA·cm^(-2)for oxygen evolution reaction.The assembled quasi-solid-state zinc-air battery using PtFeCoNiMn/NC as air electrode shows a high peak power density of 192.16 mW·cm^(-2),low charge−discharge voltage gap,and excellent durability over 500 cycles at 5 mA·cm^(-2).This work demonstrates an effective route for rational design of bifunctional nanostructured HEA electrocatalysts with favorable electronic structures,and opens up a fascinating directions for energy storage and conversion,and beyond.