MOF-Transformed In_(2)O_(3-x)@C Nanocorn Electrocatalyst for Efficient CO_(2)Reduction to HCOOH

For electrochemical CO_(2) reduction to HCOOH,an ongoing challenge is to design energy efficient electrocatalysts that can deliver a high HCOOH current density(JHCOOH)at a low overpotential.Indium oxide is good HCOOH production catalyst but with low con-ductivity.In this work,we report a unique corn design of In_(2)O_(3-x)@C nanocatalyst,wherein In_(2)O_(3-x)nanocube as the fine grains dispersed uniformly on the carbon nanorod cob,resulting in the enhanced conductivity.Excellent performance is achieved with 84%Faradaic efficiency(FE)and 11 mA cm^(−2)JHCOOH at a low potential of−0.4 V versus RHE.At the current density of 100 mA cm^(−2),the applied potential remained stable for more than 120 h with the FE above 90%.Density functional theory calculations reveal that the abundant oxygen vacancy in In_(2)O_(3-x) has exposed more In^(3+) sites with activated electroactivity,which facilitates the formation of HCOO*intermediate.Operando X-ray absorp-tion spectroscopy also confirms In^(3+) as the active site and the key intermediate of HCOO*during the process of CO_(2) reduction to HCOOH.

Antioxidative solution processing yields exceptional Sn(Ⅱ) stability for sub-1.4 eV bandgap inorganic perovskite solar cells

Owing to the combined features of sub-1.4 eV bandgap and all-inorganic composition,cesium tin–lead(Sn-Pb)triiodide perovskite is promising for approaching the Shockley-Queisser limit of solar cells while avoiding the use of volatile organic cations.But the low Sn(Ⅱ)stability in this perovskite remains a hurdle for delivering its theoretically attainable device performance.Herein we present a synthesis method of this perovskite based on an acetylhydrazine-incorporated antioxidative solution system.Mechanistic investigation shows that acetylhydrazine effectively reduces the oxidation of solution-phase Sn(Ⅱ)and meanwhile creates an electron-rich,protective nano-environment for solid-state Sn(Ⅱ)ions.These lead to high oxidation resistance of the final film as well as effective defect inhibition.The resultant solar cells demonstrate power conversion efficiencies up to 15.04%,the highest reported so far for inorganic perovskite devices with sub-1.4 eV bandgaps.Furthermore,the T_(90) lifetime of these devices can exceed 1000 hours upon light soaking in a nitrogen atmosphere,demonstrating the potential advantage when lower-bandgap perovskite solar cells go all-inorganic.

Cu-substitution P2-Na_(0.66)Mn_(1-x)Cu_(x)O_(2) sodium-ion cathode with enhanced interlayer stability

P2-type Mn-based layered oxides are viewed as promising cathode materials for sodium ion battery by virtue of their high theoretical capacity.Considering that pure Na_(2/3)MnO_(2)suffers from poor cycling performances,Cu-substitution strategy is proposed to effectively alleviate this issue.However,the structural evolution mechanism of the Cu-containing samples still remains unclear.Herein,we propose that CuSubstitution P2-type Na_(0.66)Mn_(1-x)Cu_(x)O_(2)with enlarged lattice parameters are conducive to improving the interlayer structure stability through mitigating TMO_(2)slabs distortion.Proved by synchrotron XAS spectra and ex/in situ XRD,the expansion/contraction of MnO_6 octahedron is dramatically reduced with the increased Cu content,showing the facilitated Na ion diffusion.Furthermore,when the ratio of Cu to Mn reaches 1:4,the phase transition from P2 to P'2 type at the end of discharge can be suppressed,resulting in the improved interlayer skeleton stability.The Cu-containing samples with stable interlayer structure exhibit high capacity retention and outstanding rate performances(a capacity of 79.9 m Ah g^(-1)at 5C).This Cu-substitution strategy provides a promising approach to designing highly stable cathodes.

高价阳离子(Al^(3+))诱导的Na_(4)Fe_(3)(PO_(4))_(2)(P_(2)O_(7))正极助力构筑全气候钠离子全电池

Na_(4)Fe_(3)(PO_(4))_(2)(P_(2)O_(7))(NFPP)is currently drawing increased attention as a sodium-ion batteries(SIBs)cathode due to the cost-effective and NASICON-type structure features.Owing to the sluggish electron and Na~+conductivities,however,its real implementation is impeded by the grievous capacity decay and inferior rate capability.Herein,multivalent cation substituted microporous Na_(3.9)Fe_(2.9)Al_(0.1)(PO_(4))_(2)(P_(2)O_(7))(NFAPP)with wide operation-temperature is elaborately designed through regulating structure/interface coupled electron/ion transport.Greatly,the derived Na vacancy and charge rearrangement induced by trivalent Al^(3+)substitution lower the ions diffusion barriers,thereby endowing faster electron transport and Na^(+)mobility.More importantly,the existing Al-O-P bonds strengthen the local environment and alleviate the volume vibration during(de)sodiation,enabling highly reversible valence variation and structural evolution.As a result,remarkable cyclability(over 10,000 loops),ultrafast rate capability(200 C),and exceptional all-climate stability(-40-60℃)in half/full cells are demonstrated.Given this,the rational work might provide an actionable strategy to promote the electrochemical property of NFPP,thus unveiling the great application prospect of sodium iron mixed phosphate materials.

Crack-free single-crystalline Co-free Ni-rich LiNi_(0.95)Mn_(0.05)O_(2) layered cathode

The rapid growth in global electric vehicles(EVs)sales has promoted the development of Co-free,Ni-rich layered cathodes for state-of-the-art high energy-density,inexpensive lithium-ion batteries(LIBs).However,progress in their commercial use has been seriously hampered by exasperating performance deterioration and safety concerns.Herein,a robust single-crystalline,Co-free,Ni-rich LiNi_(0.95)Mn_(0.05)O_(2)(SC-NM95)cathode is successfully designed using a molten salt-assisted method,and it exhibits better structural stability and cycling durability than those of polycrystalline LiNi_(0.95)Mn_(0.05)O_(2) (PC-NM95).Notably,the SC-NM95 cathode achieves a high discharge capacity of 218.2 mAh g^(-1),together with a high energy density of 837.3 Wh kg^(-1) at 0.1 C,mainly due to abundant Ni^(2+)/Ni^(3+) redox.It also presents an outstanding capacity retention(84.4%)after 200 cycles at 1 C,because its integrated single-crystalline structure effectively inhibits particle microcracking and surface phase transformation.In contrast,the PC-NM95 cathode suffers from rapid capacity fading owing to the nucleation and propagation of intergranular microcracking during cycling,facilitating aggravated parasitic reactions and rocksalt phase accumulation.This work provides a fundamental strategy for designing high-performance singlecrystalline,Co-free,Ni-rich cathode materials and also represents an important breakthrough in developing high-safe,low-cost,and high-energy LIBs.

基于阳离子势设计高性能P2/O3共生复合相储钠正极材料

含钠层状氧化物比容量高、结构多样、组分可调、制备简单,是极具前景的钠离子电池正极材料之一.其中,P2型和O3型层状氧化物因结构的差异表现出了不同的性能特点,制备P2/O3复合相材料可在一定程度上耦合二者的优势.然而,这种复合相材料的形成机制尚不明确,材料设计缺乏指导依据.对此,本文基于阳离子势观点系统研究了P2/O3复合相的形成机制,证明了P2/03双相结构本质上源于反应热力学/动力学因素导致的元素分布不均匀性及其引起的局部阳离子势差异,进一步提出了具有普适性的“临界阳离子势+调控组分熵”材料设计原则,并阐释了以P2/O3相竞争反应为主的复合相“协同效应”,为钠离子电池新型氧化物正极材料的设计开发提供了理论依据.