The Preparation And Performance Study On Ru Electrocatalysts Toward Alkaline Hydrogen Oxidation Reaction

Hydroxide exchange membrane fuel cells（HEMFCs）switch the operating environment from an acidic to a basic one.However,even for the case of Pt/C electrocatalyst,the reaction rate of anodic hydrogen oxidation reaction（HOR）in alkaline medium is 1-2 orders of magnitude lower than that in acidic medium.As a result,when the performance of HEMFCs can be comparable to that of proton exchange membrane fuel cells（PEMFCs）,a high loading of Pt needs to be sprayed at the anode side of HEMFCs.In view of the high cost and scarcity of Pt,the development of low-Pt or Pt-free alkaline HOR electrocatalysts with high efficiency,stability and low cost is very important for the commercial development of HEMFCs.The Ru has similar properties to Pt,but its price is only half of Pt,so it is recognized as a potential anode electrocatalyst to replace Pt.However,the activity and stability of Ru decreases significantly at high anodic potential.In this paper,focusing on the above issues,two Ru-based electrocatalysts are studied,the main contents are as follows:（1）Pt Ru nanoparticles（NPs）uniformly dispersed on porous nitrogen-doped carbon via an ethylene glycol reduction method,where porous nitrogen-doped support（NC-ZG）is prepared by the low-temperature pyrolysis of an in-situ grown ZIF-8/graphere oxide（GO）nanocomposite.The as-obtained Pt Ru_0.6/NC-ZG electrocatalyst shows a mass specific exchange current density(j_0,m)of 1102 A g^-1_{Pt Ru},superior to reference Pt Ru_0.6/NC-Z with only ZIF-8 pyrolyzed as carbon support(312A g^-1_{Pt Ru})and the commercial Pt/C(224 A g^-1_{Pt Ru}).The splendid property is contributed to the rich micro-mesopores structure,large specific surface area,high conductivity,and electronic effects between Pt and Ru for the optimization of OH_adsand H_ads binding energy.Moreover,Pt Ru_0.6/NC-ZG also displays good stability with66.4%of j_0,m remained after the accelerated durability tests,outperforming the commercial Pt/C（45.9%）.（2）Ru O₂-Pd O heterostructure nanowire networks（NWs）with rich interfaces and defects supported on carbon（Ru O₂-Pd O NWs/C）for alkaline hydrogen oxidation reaction（HOR）was formed by a seed induction-oriented attachment-thermal treatment method for the first time.As expected,the Ru O ₂-Pd O NWs/C（72.8%Ru atomic content in metal）exhibits an excellent activity in alkaline HOR with j_0,m of1061 A g^-1_{Ru Pd},which is 3.1 times of commercial Pt/C(338 A g _Pt^-1)and better than most of the reported non-Pt noble metal HOR electrocatalysts.Even at the high potential（～0.5 V vs.RHE）or the presence of CO（5 vol%）,the Ru O ₂-Pd O NWs/C still remains effectively catalyze the alkaline HOR.Structure/electrochemical analysis and theoretical calculations reveal that the interfaces between Ru O₂ and Pd O act as active sites.The electronic interactions between the two species and rich defects weaken the adsorption of H_ad and strengthen the adsorption of OH_ad,accelerating the alkaline HOR process.Moreover,OH_ad on Ru O₂ can spillover to the interfaces,providing more intermediates for reaction and simultaneously keeping the stable current density at higher potential.