Complex Alloy and Heterostructure Nanoparticles Derived from Perovskite Oxide Precursors for Catalytic Dry Methane Reforming

We have developed a general route for combining Ni, Fe, Co, Cu, and Pd in a nanoparticle using the exsolution mechanism from LaFe0.7Ni0.1Co0.1Cu0.05Pd0.05O3 perovskite oxide precursors. The strong adherence of the nanoparticles to the support yields attractive catalytic properties for dry methane reforming, such as coke resistance and thermal sintering suppression. The reduction of the precursors at 700 and 900 °C yielded NiCoCuPd or NiFeCoCuPd nanoparticles with a size-dependent phase transition from a complex concentrated alloy to phase-separated heterostructures. Our findings indicate that smaller concentrated alloy nanoparticles (∼10 nm) are more effective for methane activation than larger (>20 nm) phase-separated nanoparticles

Pt₃Co/Co Composite Catalysts on Porous N‑Doped Carbon Support Derived from ZIF-67 with Enhanced HER and ORR Activities

The primary challenge for efficient H2 evolution and hydrogen energy conversion is to develop highly active and stable catalysts with simple and reliable preparation processes. In this regard, we have designed and synthesized a porous carbon-supported low-Pt alloy catalyst (Pt3Co/Co@C composite) using ZIF-67 as a template. It showed uniformly dispersed Pt3Co/Co on the porous carbon layer due to the confinement effect of the porous carbon layer. Pt3Co/Co@C demonstrated excellent activity for the hydrogen evolution reaction in the full pH range, with an overpotential of 187 mV in 0.5 M H2SO4 to attain 100 mA/cm2 as well as long-term stability. It also displayed superior mass activity for the oxygen reduction reaction (ORR) at 0.85 V (vs RHE) compared to the commercial Pt/C. Furthermore, the Pt3Co/Co@C catalyst exclusively enabled a four-electron reaction process under ORR conditions without the competitive pathway to H2O2. The current work provides guidance for the design and facile synthesis of Pt-based catalysts with enhanced performance

Dynamical Observation and Detailed Description of Catalysts under Strong Metal–Support Interaction

Understanding the structures of catalysts under realistic conditions with atomic precision is crucial to design better materials for challenging transformations. Under reducing conditions, certain reducible supports migrate onto supported metallic particles and create strong metal–support states that drastically change the reactivity of the systems. The details of this process are still unclear and preclude its thorough exploitation. Here, we report an atomic description of a palladium/titania (Pd/TiO₂) system by combining state-of-the-art in situ transmission electron microscopy and density functional theory (DFT) calculations with structurally defined materials, in which we visualize the formation of the overlayers at the atomic scale under atmospheric pressure and high temperature. We show that an amorphous reduced titania layer is formed at low temperatures, and that crystallization of the layer into either mono- or bilayer structures is dictated by the reaction environment and predicted by theory. Furthermore, it occurs in combination with a dramatic reshaping of the metallic surface facets

Cumulative ET for each year of 2003–2010 respectively (panel a); cumulative ET averaged over the observation periods and its standard deviation (black line) and monthly variations in standard deviation (red line and the axis on right) (panel b).

<p>Cumulative ET for each year of 2003–2010 respectively (panel a); cumulative ET averaged over the observation periods and its standard deviation (black line) and monthly variations in standard deviation (red line and the axis on right) (panel b).</p

Coefficient of variation (CV) of ET at flux sites with over 3 years' observations.

<p>Coefficient of variation (CV) of ET at flux sites with over 3 years' observations.</p

Cumulative precipitation versus average air temperature of the whole year and the growing season (April–October) during the period 1989–2010.

<p>For the period of 2003–2010, the size of black dot is approximately proportional to the ET amount. The two-digit numbers (YY) denote the years from 2003 to 2010 (20YY). Dotted lines represent the averages over the 20 year period.</p

Yearly values of cumulative ET calculated through different approaches: V_cli-eco (for variable climate and variable ecosystem responses); V_cli (for variable climate); V_eco (for variable ecosystem responses).

<p>The correlation coefficients of the cumulative values calculated with the three approaches are also reported.</p

Annual accumulated ET, R_n, P and annual averaged T_a during 2003–2010.

<p>Annual accumulated ET, R_n, P and annual averaged T_a during 2003–2010.</p

Air temperature (T_a °C) and growing season length (GSL, in days T_a≥5°C) during 2003–2010.

<p>Air temperature (T_a °C) and growing season length (GSL, in days T_a≥5°C) during 2003–2010.</p

Correlation coefficients (R) between ET and some of the climatic drivers (R_n, T_a and VPD) at monthly and annual scale (p represents the probability-value).

<p>Correlation coefficients (R) between ET and some of the climatic drivers (R_n, T_a and VPD) at monthly and annual scale (p represents the probability-value).</p