Hollow FeCo-FeCoP@C nanocubes embedded in nitrogen-doped carbon nanocages for efficient overall water splitting

Designing readily available and highly active electrocatalysts for water splitting is essential for renewable energy technologies.Here we present the construction of FeCo-FeCoP@C hollow nanocubes encapsulated in nitrogen-doped carbon nanocages(FeCo-FeCoP@C@NCCs) through controlled carbonization and subsequent phosphorization of a Prussian blue analogue.With stronger electronic interaction and hollow structure,the as-obtained FeCo-FeCoP@C@NCCs material requires small overpotentials of 91 mV and280 mV to deliver 10 mA cm^(-2) in 1 M KOH toward hydrogen and oxygen evolution,respectively.More importantly,applying this material for overall water splitting,it only requires 1.64 V to afford10 mA cm^(-2) and exhibits impressively durability over 40 h without obvious performance decay.The present approach inspires potentials for the controllable synthesis of multi-component catalysts for practical applications.

Reduction and carburization of iron oxides for Fischer–Tropsch synthesis

The activation of iron oxide Fischer–Tropsch Synthesis(FTS) catalysts was investigated during pretreatment: reduction in hydrogen followed by carburization in either CO or syngas mixture, or simultaneously reduction and carburization in syngas. A combination of different complementary in situ techniques was used to gain insight into the behavior of Fe-based FTS catalysts during activation. In situ XRD was used to identify the crystalline structures present during both reduction in hydrogen and carburization. An increase in reduction rate was established when increasing the temperature. A complete reduction was demonstrated in the ETEM and a grain size dependency was proven, i.e. bigger grains need higher temperature in order to reduce. XPS and XAS both indicate the formation of a small amount of carbonaceous species at the surface of the bulk metallic iron during carburization.

Fe5C2 nanoparticles as low-cost HER electrocatalyst:the importance of Co substitution

Constructing and understanding the doping effect of secondary metal in transition metal carbide(TMC)catalysts is pivotal for the design of low-cost hydrogen evolution reaction(HER) electrocatalysts. In this work, we developed a wet-chemistry strategy for synthesizing Co-modified Fe_5C_2 nanoparticles((Fe_(1-x)Cox)_5C_2 NPs) as highly active HER electrocatalysts in basic solution. The structure of(Fe_(1-x)Cox)_5C_2 NPs was characterized by X-ray diffraction(XRD), extended X-ray absorption fine structure spectra(EXAFS) and scanning/transmission electron microscopy(S/TEM), indicating that the isomorphous substitution of cobalt in the lattice of Fe_5C_2.(Fe_(0.75) Co_(0.25))_5C_2 exhibited the best HER activity(174 mV for j = -10 mA/cm^2). Computational calculation results indicate that Co provides the most active site for HER. X-ray adsorption spectra(XAS) studies further suggested that the electron transfer in Fe–C bonds are enhanced by the substitution of Co, which modulates the hydrogen adsorption on the adjacent electronic-enriched carbon, and therefore promotes HER activity. Our results affirm the design of lowcost bimetallic TMCs based HER catalysts.

Mild and selective hydrogenation of CO2 into formic acid over electron-rich MoC nanocatalysts

The direct hydrogenation of CO2 using H2 gas is a one-stone-two-birds route to produce highly valueadded hydrocarbon compounds and to lower the CO2 level in the atmosphere.However,the transformation of CO2 and H2 into hydrocarbons has always been a great challenge while ensuring both the activity and selectivity over abundant-element-based nanocatalysts.In this work,we designed a Schottky heterojunction composed of electron-rich MoC nanoparticles embedded inside an optimized nitrogen-doped carbon support(MoC@NC)as the first example of noble-metal-free heterogeneous catalysts to boost the activity of and specific selectivity for CO2 hydrogenation to formic acid(FA)in liquid phase under mild conditions(2 MPa pressure and 70℃).The MoC@NC catalyst with a high turnover frequency(TOF)of 8.20 molFA molMoC^-1 h^-1 at 140℃ and an excellent reusability are more favorable for real applications.