Ru single atoms induce surface-mediated discharge in Na-O_(2)batteries

Sodium(Na)O_(2)batteries have high energy density and low cost.However,high polarization,complex discharge products,and low Coulombic efficiency(CE)lead to poor cyclability.Here,we proposed an atomically dispersed Ru catalyst on nitrogen-doped graphene for Na-O_(2)batteries.The catalysts enable the discharge to proceed via a surface-mediated route,which leads to uniform deposition of Na_(2-x)O_(2)and low polarization during recharge.The first-principle calculation revealed that Ru-N_(4)complex in the catalyst has strong chemical adsorption to intermediate superoxides,facilitating uniform deposition and enhancing rapid kinetics.In contrast,Ru nanoparticles,despite the catalytic activity,induce bulk deposition via a solution-mediated route because the exposed graphene surface shows weak interaction to superoxides,thereby lowering CEs and cyclability.In brief,the atomically-dispersed Ru catalyst endows Na-O_(2)batteries with excellent electrochemical properties via a surface-mediated discharge.

Micropore-confined Ru nanoclusters catalyst for efficient pHuniversal hydrogen evolution reaction

Pt-based catalysts are used commercially for the hydrogen evolution reaction(HER),even though the low earth abundance and high cost of platinum hinder scale-up applications.Ru metal is a promising alternative catalyst for HER owing to its lower cost but similar metal-hydrogen bond strength to Pt.However,designing an efficient and robust Ru-based electrocatalyst for pHuniversal HER is challenging.Herein,we successfully synthesized N-doped carbon(NC)supported ruthenium catalysts with different Ru sizes(single-atoms,nanoclusters and nanoparticles),and then systematically evaluated their performance for HER.Among these catalysts,the Ru nanocluster catalyst(Ru NCs/NC)displayed optimal catalytic performance with overpotentials of only 14,30,and 32 mV(at 10 mA·cm^(-2))in 1 M KOH,1 M phosphate buffer saline(PBS),and 0.5 M H_(2)SO_(4),respectively.The corresponding mass activities were 32.2,12.1 and 8.1 times higher than those of 20 wt.%Pt/C,and also much better than those of the Ru single-atoms(Ru SAs/NC)and Ru nanoparticle(Ru NPs/NC)catalysts,at an overpotential of 100 mV under alkaline,neutral and acidic conditions,respectively.Density functional theory(DFT)calculations revealed that the outstanding HER performance of the Ru NCs/NC catalyst resulted from a strong interaction between the Ru nanoclusters and the N-doped carbon support,which downshifted the d-band center and thus weakened the*H adsorption ability of Ru sites.

Atomically Dispersed Ru-Decorated TiO_(2) Nanosheets for Thermally Assisted Solar-Driven Nitrogen Oxidation into Nitric Oxide

Thermally assisted photodriven nitrogen oxidation to nitric oxide(NO)using air as a reactant is a promising way to supersede the traditional NO synthesis industry accompanied by huge energy expenditure and greenhouse gas emission.Meanwhile,breaking the N≡N triple bond(941 kJ·mol^(−1))in nitrogen is still challenging,and the development of more efficient catalysts is necessary.Herein,Ru single atoms decorated TiO_(2) nanosheets(Ru SAs/TiO_(2))were constructed and achieved superior performance for NO photosynthesis with a product rate of 192μmol g^(−1) h^(−1) and a quantum efficiency of 0.77% at 365 nm.Both ^(15)N isotope labeling experiments and in situ near ambient pressure X-ray photoelectron spectroscopy(in situ NAP-XPS)proved the origin of NO from N_(2) photooxidation.A series of in situ characterizations and theoretical calculations unveiled the reaction pathway of nitrogen photooxidation.Breaking the O-O bond to form(N-O)2-Ru intermediates was demonstrated as the rate-determining step.Importantly,a single-atomic structure was proven to inhibit the aggregation and inactivation of Ru,leading to outstanding durability.