Spin regulation on(Co,Ni)Se_(2)/C@FeOOH hollow nanocage accelerates water oxidation

Spin engineering is recognized as a promising strategy that modulates the association between d‐orbital electrons and the oxygenated species,and enhances the catalytic kinetics.However,few efforts have been made to clarify whether spin engineering could make a considerable enhancement for electrocatalytic water oxidation.Herein,we report the spin engineering of a nanocage‐structured(Co,Ni)Se_(2)/C@FeOOH,that showed significant oxygen evolution reaction(OER)activity.Magnetization measurement presented that the(Co,Ni)Se_(2)/C@FeOOH sample possesses higher polarization spin number(μb=6.966μB/f.u.)compared with that of the(Co,Ni)Se_(2)/C sample(μb=6.398μB/f.u.),for which the enlarged spin polarization number favors the adsorption and desorption energy of the intermediate oxygenated species,as confirmed by surface valance band spectra.Consequently,the(Co,Ni)Se_(2)/C@FeOOH affords remarkable OER product with a low overpotential of 241 mV at a current of 10 mA cm^(-2) and small Tafel slope of 44 mV dec^(-1) in 1.0 mol/L KOH alkaline solution,significantly surpassing the parent(Co,Ni)Se_(2)/C catalyst.This work will trigger a solid step for the design of highly‐efficient OER electrocatalysts.

Mechanistic Insights into Electrocatalytic Nitrogen Reduction Reaction on the Pd-W Heteronuclear Diatom Supported on C_(2)N Monolayer:Role of H Pre-Adsorption

The electrocatalytic N_(2) reduction reaction(eNRR)is a potential alternative to the Haber-Bosch process for ammonia(NH3)production.Tremendous efforts have been made in eNRR catalyst research to promote the practical application of eNRR.In this work,by means of density functional theory calculations and the computational hydrogen electrode model,we evaluated the eNRR performance of 30 single metal atoms supported on a C_(2)N monolayer(M@C_(2)N),and we designed a new thermodynamically stable Pd-W hetero-metal diatomic catalyst supported on the C_(2)N monolayer(PdW@C_(2)N).We found that PdW@C_(2)N prefers to adsorb H over N_(2),and then,the pre-generated hydrogen-terminated PdW@C_(2)N selectively adsorbing N_(2) behaves as the actual functioning“catalyst”to catalyze the eNRR process,exhibiting excellent performance with a low overpotential(0.31 V),an ultralow NH3 desorption free energy(0.05 eV),and a high selectivity toward eNRR over hydrogen evolution reaction(HER).Moreover,PdW@C_(2)N shows a superior eNRR performance to its monomer(W@C_(2)N)and homonuclear diatom(W_(2)@C_(2)N)counterparts.The revealed mechanism indicates that the preferential H adsorption over N_(2) on the active site may not always hamper the eNRR process,especially for heteronuclear diatom catalysts.This work encourages deeper exploration on the competition of eNRR and HER on catalyst surfaces.

Rationally tailoring interface characteristics of ZnO/amorphous carbon/graphene for heat-conduction microwave absorbers

With the increasingly severe electromagnetic interference issue and the huge heat dissipation demand caused by the miniaturized and integrated electronic devices,exploring the heat-conduction microwave absorption(MA)materials is highly desired and remains a great challenge.Herein,we reported the fabrication of ZnO/amorphous carbon(ZnO/AC)hybrid films covered on the surface of graphene(ZnO/AC/Graphene)to simultaneously apply as the MA and thermal management materials.The ZnO/AC coatings synthesized with the auxiliary of an atomic layer deposition(ALD)method are highly uniform and controllable,which can significantly improve the MA performance and thermal conduction properties of graphene.The reflection loss(RL)of−55.4 dB and the effective absorption bandwidth of 5.3 GHz were achieved with thickness of 2.0 mm for ZnO/AC/Graphene at a low loading content(3 wt.%).The minimum RL of−57.9 dB can be obtained in the ZnO/AC/Graphene composites at a low frequency(7.8 GHz).Moreover,the absorption frequency can be regulated by changing the ZnO/AC which can be readily implemented by adjusting the ALD cycles of ZnO.The thermal conductivity of ZnO/AC/Graphene is up to 257.8 mW·m^(−1)·K^(−1),increased by 53.2%compared with natural rubber.The enhancement mechanisms of microwave loss and heat conduction are systematically studied in detail.This work not only develops an excellent candidate,but also provides a novel strategy to design functional materials for heat-conduction MA application.

Metal-Organic Frameworks Offering Tunable Binary Active Sites toward HighlyEfficient Urea Oxidation Electrolysis

Electrocatalytic urea oxidation reaction(UOR)is regarded as an effective yet challenging approach for the degradation of urea in wastewater into harmless N2 and CO_(2).To overcome the sluggish kinetics,catalytically active sites should be rationally designed to maneuver the multiple key steps of intermediate adsorption and desorption.Herein,we demonstrate that metal-organic frameworks(MOFs)can provide an ideal platform for tailoring binary active sites to facilitate the rate-determining steps,achieving remarkable electrocatalytic activity toward UOR.Specifically,the MOF(namely,NiMn_(0.14)-BDC)based on Ni/Mn sites and terephthalic acid(BDC)ligands exhibits a low voltage of 1.317 V to deliver a current density of 10 mA cm^(-2).As a result,a high turnover frequency(TOF)of 0.15 s^(-1) is achieved at a voltage of 1.4 V,which enables a urea degradation rate of 81.87%in 0.33 M urea solution.The combination of experimental characterization with theoretical calculation reveals that the Ni and Mn sites play synergistic roles in maneuvering the evolution of urea molecules and key reaction intermediates during the UOR,while the binary Ni/Mn sites in MOF offer the tunability for electronic structure and d-band center impacting on the intermediate evolution.This work provides important insights into active site design by leveraging MOF platform and represents a solid step toward highly efficient UOR with MOF-based electrocatalysts.

Kinetics of the Toluene Reaction with OH Radical

We calculated the kinetics of chemical activation reactions of toluene with hydroxyl radical in the temperature range from 213 K to 2500 K and the pressure range from 10 Torr to the high-pressure limit by using multistructural variational transition state theory with the small-curvature tunneling approximation(MS-CVT/SCT)and using the system-specifc quantum Rice-RamspergerKassel method.Te reactions of OH with toluene are important elementary steps in both combustion and atmospheric chemistry,and thus it is valuable to understand the rate constants both in the high-pressure,high-temperature regime and in the low-pressure,low-temperature regime.Under the experimental pressure conditions,the theoretically calculated total reaction rate constants agree well with the limited experimental data,including the negative temperature dependence at low temperature.We fnd that the efect of multistructural anharmonicity on the partition functions usually increases with temperature,and it can change the calculated reaction rates by factors as small as 0.2 and as large as 4.2.We also fnd a large efect of anharmonicity on the zero-point energies of the transition states for the abstraction reactions.We report that abstraction of H from methyl should not be neglected in atmospheric chemistry,even though the low-temperature results are dominated by addition.We calculated the product distribution,which is usually not accessible to experiments,as a function of temperature and pressure.