Fe3C coupled with Fe-Nx supported on N-doped carbon as oxygen reduction catalyst for assembling Zn-air battery to drive water splitting

The emergence of nanomaterials (NMs) has made everyone more aware of the close relationship between the size and performance of materials. Especially, the catalytic properties of materials may change dramatically when the macroscopic size of matter goes from bulk to nanometer to atomic level. It is very firmly believed that “Small size determines macroproperties, contains big science.” Therefore, as chemists hope, it is very essential to rationally tune and characterize the size of materials and deeply understand the relationship between macroscopic catalytic properties and small structures. Herein, the recent progress in both multi‐scale materials from nanoscale, sub‐nano, clusters to atomic scale for various catalytic reactions is focused. Specifically, the catalytic reaction on the microstructures and the relationship between the small scale and big science are comprehensively summarized and discussed. This review systematically spans dimensions to reveal the catalytic performances of materials at different scales with a unique effect. This is crucial for rationally understanding the composition of materials and exploring their catalytic activity. Current opportunities, future challenges, and outlooks for the application of multiscale materials (NMs, sub‐nano, cluster, and atomically dispersed materials) in catalysis, energy and environmental protection, etc. are summarized and outlined.

Small‐Scale Big Science: From Nano‐ to Atomically Dispersed Catalytic Materials

Surface strain engineering is a promising strategy to design various electrocatalysts for sustainable energy storage and conversion. However, achieving the multifunctional activity of the catalyst via the adjustment of strain engineering remains a major challenge. Herein, an excellent trifunctional electrocatalyst (Ru/RuO2@NCS) is prepared by anchoring lattice mismatch strained core/shell Ru/RuO2 nanocrystals on nitrogen-doped carbon nanosheets. Core/shell Ru/RuO2 nanocrystals with ~5 atomic layers of RuO2 shells eliminate the ligand effect and produce ~2% of the surface compressive strain, which can boost the trifunctional activity (oxygen evolution reaction [OER], oxygen reduction reaction [ORR], and hydrogen evolution reaction [HER]) of the catalyst. When equipped in rechargeable Zn-air batteries, the Ru/RuO2@NCS endows them with high power (137.1 mW cm−2) and energy (714.9 Wh kgZn−1) density and excellent cycle stability. Moreover, the as-fabricated Zn-air batteries can drive a water splitting electrolyzer assembled with Ru/RuO2@NCS and achieve a current density of 10 mA cm−2 only requires a low potential ~1.51 V. Density functional theory calculations reveal that the compressive strained RuO2 could reduce the reaction barrier and improve the binding of rate-determining intermediates (*OH, *O, *OOH, and *H), leading to the enhanced catalytic activity and stability. This work can provide a novel avenue for the rational design of multifunctional catalysts in future clean energy fields. 

https://onlinelibrary.wiley.com/doi/pdfdirect/10.1002/inf2.12326

Activating ruthenium dioxide via compressive strain achieving efficient multifunctional electrocatalysis for Zn‐air batteries and overall water splitting

Why the microkinetic modeling of experimental tafel plots requires knowledge of the reaction intermediate's binding energy

Single-metal-atom chains (SMACs), as the smallest one-dimensional structure, have intriguing physical and chemical properties. Although several SMACs have been realized so far, their controllable fabrication remains challenging due to the need to arrange single atoms in an atomically precise manner. Here we develop a chemical vapour co-deposition method to construct a wafer-scale network of platinum SMACs in atom-thin films. The obtained atomic chains possess an average length of up to ~17 nm and a high density of over 10 wt%. Interestingly, as a consequence of the electronic delocalization of platinum atoms along the chain, this atomically coherent one-dimensional channel delivers a metallic behaviour, as revealed by electronic measurements, first-principles calculations and complex network modelling. Our strategy is potentially extendable to other transition metals such as cobalt, enriching the toolbox for manufacturing SMACs and paving the way for the fundamental study of one-dimensional systems and the development of devices comprising monoatomic chains. The fabrication of single-metal-atom chains in an atomically precise way is challenging. Now, a chemical vapour co-deposition method is reported for the synthesis of highly ordered single-atom chains of platinum with lengths of up to 20 nm on a wafer-scale. The metallic behaviour of the single-metal-atom chain is revealed by electronic measurements, first-principle calculations and complex network modelling. 

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Direct growth of single-metal-atom chains

Improved activity and stability Pt-based catalysts for the oxygen reduction reaction (ORR) are needed to perpetuate the deployment of polymer electrolyte fuel cells (PEFCs) in the transportation sector. Here, we use atomic layer deposition of TiO2 and Pt coupled with thermal reductive annealing to prepare Pt3Ti electrocatalysts. The atomic level synthetic control resulted in Pt3Ti nanoparticles with high ORR performance, including a mass activity of 1.84 A/mgPt and excellent electrochemical stability. The Pt3Ti nanoparticles show excellent specific activity — 5.3-fold higher than commercial Pt/C and 3-fold higher than polycrystalline Pt, exceeding the performance of any PtTi catalysts reported to date. Combined experimental and computational efforts indicate that Pt enrichment on the Pt3Ti enhances the activity, and the intrinsic stability of the Pt3Ti phase provides durability. This knowledge, along with the facile fabrication of alloys by atomic layer deposition, can be leveraged to designed improved performance catalysts.

Improving intrinsic oxygen reduction activity and stability: Atomic layer deposition preparation of platinum-titanium alloy catalysts

The design and fabrication of lattice-strained platinum catalysts achieved by removing a soluble core from a platinum shell synthesized via atomic layer deposition, is reported. The remarkable catalytic performance for the oxygen reduction reaction (ORR), measured in both half-cell and full-cell configurations, is attributed to the observed lattice strain. By further optimizing the nanoparticle geometry and ionomer/carbon interactions, mass activity close to 0.8 A mgPt-1 @0.9 V iR-free is achievable in the membrane electrode assembly. Nevertheless, active catalysts with high ORR activity do not necessarily lead to high performance in the high-current-density (HCD) region. More attention shall be directed toward HCD performance for enabling high-power-density hydrogen fuel cells.

https://onlinelibrary.wiley.com/doi/pdf/10.1002/adma.202007885

Direct Integration of Strained-Pt Catalysts into Proton-Exchange-Membrane Fuel Cells with Atomic Layer Deposition

Computational design of high-functioning electrocatalysts is an integral part of catalyst discovery. However, as we approach the limits of performance imposed by scaling relations, finding active c...

Olga Vinogradova

Papers

Improving intrinsic oxygen reduction activity and stability: Atomic layer deposition preparation of platinum-titanium alloy catalysts

Direct Integration of Strained-Pt Catalysts into Proton-Exchange-Membrane Fuel Cells with Atomic Layer Deposition

Distinguishing Among High Activity Electrocatalysts: Regression vs Classification