Oxygen Vacancy-induced Electron Density Tuning of Fe_(3)O_(4) for Enhanced Oxygen Evolution Catalysis

Despite the tremendous efforts devoted to enhancing the activity of oxygen evolution reaction(OER)catalysts,there is still a huge challenge to deeply understand the electronic structure characteristics of transition metal oxide to guide the design of more active catalysts.Herein,Fe_(3)O_(4)with oxygen vacancies(Fe_(3)O_(4)-Vac)was synthesized via Ar ion irradiation method and its OER activity was greatly improved by properly modulating the electron density around Fe atoms.The electron density of Fe_(3)O_(4)-Vac around Fe atoms increased compared to that of Fe_(3)O_(4)according to the characterization of synchrotron-based X-ray absorption near-edge structure(XANES),extended X-ray absorption fine structure(EXAFS)spectra,and density functional theory(DFT)calculation.Moreover,the DFT results indicate the enhancement of the desorption of HOO^(*)groups which significantly reduced the OER reaction barrier.Fe_(3)O_(4)-Vac catalyst shows an overpotential of 353 m V,lower than that of Fe OOH(853 m V)and Fe_(3)O_(4)(415 m V)at 10 m A cm^(-2),and a low Tafel slope of 50 m V dec^(-1)in 1 M KOH,which was even better than commercial RuO_(2)at high potential.This modulation approach provides us with valuable insights for exploring efficient and robust water-splitting electrocatalysts.

In-situ structural evolution of Bi_(2)O_(3) nanoparticle catalysts for CO_(2) electroreduction

Under the complex external reaction conditions,uncovering the true structural evolution of the catalyst is of profound significance for the establishment of relevant structure–activity relationships and the rational design of electrocatalysts.Here,the surface reconstruction of the catalyst was characterized by ex-situ methods and in-situ Raman spectroscopy in CO_(2)electroreduction.The final results showed that the Bi_(2)O_(3) nanoparticles were transformed into Bi/Bi_(2)O_(3) two-dimensional thin-layer nanosheets(NSs).It is considered to be the active phase in the electrocatalytic process.The Bi/Bi_(2)O_(3) NSs showed good catalytic performance with a Faraday efficiency(FE)of 94.8%for formate and a current density of 26 mA cm^(−2) at−1.01 V.While the catalyst maintained a 90%FE in a wide potential range(−0.91 V to−1.21 V)and long-term stability(24 h).Theoretical calculations support the theory that the excellent performance originates from the enhanced bonding state of surface Bi-Bi,which stabilized the adsorption of the key intermediate OCHO^(∗) and thus promoted the production of formate.

Electronic Coupling of Single Atom and FePS_3 Boosts Water Electrolysis

Engineering the electronic structure of surface active sites at the atomic level can be an efficient way to modulate the reactivity of catalysts.Herein,we report the rational tuning of surface electronic structure of FePS_(3) nanosheets(NSs)by anchoring atomically dispersed metal atom.Theoretical calculations predict that the strong electronic coupling effect in single-atom Ni-FePS_(3) facilitates electron aggregation from Fe atom to the nearby Ni-S bond and enhances the electron-transfer of Ni and S sites,which balances the oxygen species adsorption capacity,reinforces water adsorption and dissociation process to accelerate corresponding oxygen evolution reaction(OER)and hydrogen evolution reaction(HER).The optimal Ni-FePS_(3)NSs/C exhibits outstanding electrochemical water-splitting activities,delivering an overpotential of 287 mV at the current density of 10 mA cm^(-2) and a Tafel slope of 41.1 mV dec^(-1) for OER;as well as an overpotential decrease of 219 mV for HER compared with pure FePS_(3)NSs/C.The concept of electronic coupling interaction between the substrate and implanted single active species offers an additional method for catalyst design and beyond.

The d-orbital coupling modulation of CuNi alloy for acetonitrile electrochemical reduction and in-situ hydrogenation behavior characterization

Electrochemical reduction of acetonitrile to ethylamine with a high selectivity is a novel approach to manufacture valuable primary amines which are important raw material in organic chemical industry. However, the poor ethylamine Faradic efficiency(FE_(ethylamine)) and catalyst stability at the high current density prohibit this method from being practically used. Herein, CuNi alloy ultrafine-nano-particles based on the d-orbital coupling modulation were synthesized through the electrodeposition and their catalytic performance towards acetonitrile reduction reaction(ACNRR) has been systematically studied. The highest FE_(ethylamine)(97%) is achieved with the current density of-114 mA cm^(-2). For practical application, the current density can reach-602.8 mA cm^(-2) with 82.8% FE_(ethylamine)maintained. With the appearance of other organics which co-exist with acetonitrile in the SOHIO process, CuNi can also hydrogenate acetonitrile in it with more than 80% FE_(ethylamine). Our in-situ spectroscopy analysis and DFT calculations towards the acetonitrile hydrogenation behavior reveal that the evenly dispersed Ni in Cu modulates the dband so as to endow CuNi with the better acetonitrile adsorption, milder binding energy with the reaction intermediates, smaller barrier for *CH_3CH_2NH_2 desorption and higher ability for H_2O dissociation to provide *H.

Flammable gases produced by TiO_(2) nanoparticles under magnetic stirring in water

The friction between nanomaterials and Teflon magnetic stirring rods has recently drawn much attention for its role in dye degradation by magnetic stirring in dark.Presently the friction between TiO_(2) nanoparticles and magnetic stirring rods in water has been deliberately enhanced and explored.As much as 1.00 g TiO_(2) nanoparticles were dispersed in 50 mL water in 100 mL quartz glass reactor,which got gas-closed with about 50 mL air and a Teflon magnetic stirring rod in it.The suspension in the reactor was magnetically stirred in dark.Flammable gases of 22.00 ppm CO,2.45 ppm CH_(4),and 0.75 ppm H_(2) were surprisingly observed after 50 h of magnetic stirring.For reference,only 1.78 ppm CO,2.17 ppm CH_(4),and 0.33 ppm H_(2) were obtained after the same time of magnetic stirring without TiO_(2) nanoparticles.Four magnetic stirring rods were simultaneously employed to further enhance the stirring,and as much as 30.04 ppm CO,2.61 ppm CH_(4),and 8.98 ppm H_(2) were produced after 50 h of magnetic stirring.A mechanism for the catalytic role of TiO_(2) nanoparticles in producing the flammable gases is established,in which mechanical energy is absorbed through friction by TiO_(2) nanoparticles and converted into chemical energy for the reduction of CO_(2) and H_(2)O.This finding clearly demonstrates a great potential for nanostructured semiconductors to utilize mechanical energy through friction for the production of flammable gases.

Two-dimensional PtPb-PbS heterostructure enables improved kinetics and highlighted bifunctional antipoisoning for methanol electrooxidation

Two-dimensional(2 D) platinum(Pt)-based nanomaterials are considered as the ideal fuel cell catalysts, while their rational synthesis associated with phase control remains a formidable challenge. Herein, we firstly design the novel 2 D Pt-lead-sulphur heterophased nanosheets(Pt Pb S HPNSs) as efficient high-toleration electrocatalysts for methanol oxidation reaction(MOR).They exhibit much higher activity and more highlighted bifunctional antipoisoning abilities than Pt Pb NSs and commercial Pt/C.Further density functional theory(DFT) simulation verifies that the decreased electron density of Pt sites worked by Pb and S makes CO intermediate favorable to desorb, avoiding the formation of CO*-polluted Pt sites. Simultaneously, this heterophased interface effectively weakens the adsorption of S^(2-)-species and improves the S-poisoning tolerance, showing a route to realize nearly innoxious catalysis. The present work highlights the importance of heterophase control in tuning antipoisoning property for 2 D Pt-based nanomaterials, which is key for the rational design of efficient fuel cell anodic catalysts.