Tuning Active Metal Atomic Spacing by Filling of Light Atoms and Resulting Reversed Hydrogen Adsorption-Distance Relationship for Efficient Catalysis

Precisely tuning the spacing of the active centers on the atomic scale is of great significance to improve the catalytic activity and deepen the understanding of the catalytic mechanism,but still remains a challenge.Here,we develop a strategy to dilute catalytically active metal interatomic spacing(d_(M-M))with light atoms and discover the unusual adsorption patterns.For example,by elevating the content of boron as interstitial atoms,the atomic spacing of osmium(d_(Os-Os))gradually increases from 2.73 to 2.96?.More importantly,we find that,with the increase in dOs-Os,the hydrogen adsorption-distance relationship is reversed via downshifting d-band states,which breaks the traditional cognition,thereby optimizing the H adsorption and H_2O dissociation on the electrode surface during the catalytic process;this finally leads to a nearly linear increase in hydrogen evolution reaction activity.Namely,the maximum dOs-Os of 2.96?presents the optimal HER activity(8 mV@10 mA cm^(-2))in alkaline media as well as suppressed O adsorption and thus promoted stability.It is believed that this novel atomic-level distance modulation strategy of catalytic sites and the reversed hydrogen adsorption-distance relationship can shew new insights for optimal design of highly efficient catalysts.

Single-Atom Catalysts for Electrochemical Hydrogen Evolution Reaction: Recent Advances and Future Perspectives

Hydrogen,a renewable and outstanding energy carrier with zero carbon dioxide emission,is regarded as the best alternative to fossil fuels.The most preferred route to large-scale production of hydrogen is by water electrolysis from the intermittent sources(e.g.,wind,solar,hydro,and tidal energy).However,the efficiency of water electrolysis is very much dependent on the activity of electrocatalysts.Thus,designing high-effective,stable,and cheap materials for hydrogen evolution reaction(HER)could have a substantial impact on renewable energy technologies.Recently,single-atom catalysts(SACs)have emerged as a new frontier in catalysis science,because SACs have maximum atom-utilization efficiency and excellent catalytic reaction activity.Various synthesis methods and analytical techniques have been adopted to prepare and characterize these SACs.In this review,we discuss recent progress on SACs synthesis,characterization methods,and their catalytic applications.Particularly,we highlight their unique electrochemical characteristics toward HER.Finally,the current key challenges in SACs for HER are pointed out and some potential directions are proposed as well.

Nitrogen and atomic Fe dual-doped porous carbon nanocubes as superior electrocatalysts for acidic H2-O_(2) PEMFC and alkaline Zn-air battery

Air cathodes with high electrocatalytic activity are vital for developing H2/O_(2) proton exchange membrane fuel cells(PEMFC)and Zn-air batteries.However,the state-of-the-art air cathodes suffer from either limited catalytic activity or high cost,which thus hinder their applications.Herein,we designed ZIF-8 derived nitrogen and atomic iron dual-doped porous carbon nanocubes as high-quality catalysts for ORR,through a novel gas-doping approach.The porous carbon nanocubic architecture and abundant Fe-Nxactive species endow ZIF-8 derived single atomic iron catalyst(PCN-A@Fe SA)with superior catalytic activity,and surpass Pt/C and a majority of the reported catalysts.Both XAS and DFT calculations suggest that Fe2+N4 moieties are the main active centers that are favorable for oxygen affinity and OH*intermediate desorption,which can result in promising catalytic performance.Most importantly,PCNA@Fe SA can achieve power density of 514 m W cm^(-2) as cathodic catalyst in a PEMFC and discharge peak power density of 185 m W cm^(-2) in an alkaline Zn-air battery.The outstanding performance is derived from both the high specific surface area and high-density of iron single atom in nitrogen doped nanocubic carbon matrix.

Robust MOF-253-derived N-doped carbon confinement of Pt single nanocrystal electrocatalysts for oxygen evolution reaction

Although carbon-supported platinum(Pt/C) is still considered the most active electrocatalyst for hydrogen evolution reaction(HER) and oxygen reduction reaction(ORR), its applications in metal–air batteries as a cathode catalyst, or for oxygen generation via water splitting electrolysis as an anode catalyst is mainly constrained by the insufficient kinetic activity and stability in the oxygen evolution reaction(OER). Here, MOF-253-derived nitrogen-doped carbon(N/C)-confined Pt single nanocrystals(Pt@N/C) have been synthesized and shown to be efficient catalysts for the OER. Even with low Pt mass loading of 6.1 wt%(Pt@N/C-10), the catalyst exhibits greatly improved activity and long-time stability as an efficient OER catalyst. Such high catalytic performance is attributed to the core-shell structure relationship, in which the active N-doped-C shell not only provides a protective shield to avoid rapid Pt nanocrystal oxidation at high potentials and inhibits the Pt migration and agglomeration, but also improves the conductivity and charge transfer kinetics.

Tunable Ru-Ru2P heterostructures with charge redistribution for efficient pH-universal hydrogen evolution

Designing synergistic heterogeneous catalytic interfaces is the key to developing highly compatible pH-universal electrocatalysts for complex chemical environments.Our theoretical calculation results demonstrate that the Ru-Ru2P heterointerface can not only promote the redistribution of charges,but also reduce the d-band center,and then enhances the adsorption capacity of the key intermediate.However,in situ and facile synthesis of Ru-Ru2P heterostructures is severely limited by thermodynamic obstacles.Herein,we propose a molten salt-assisted catalytic synthesis scheme,and successfully build a series of homologous metallic Ru-Ru2P heterostructure catalysts with different molar ratios of Ru to P under atmospheric pressure and low-temperature(400C).The resultant Ru-Ru2P with rich heterostructures show the Pt-like HER performance in different pH media.Particularly,it is prominent under alkaline conditions(18 mV@10 mA cm^(2)),which outperforms the Pt catalyst(37 mV@10 mA cm^(2)).Furthermore,Ru-Ru2P heterostructures also show certain potential in the electrolysis of seawater to produce hydrogen.This work represents a significant supplement of high-efficiency pH-universal HER catalysts,and provides a new light on interface engineering in energy technology fields and beyond.