In Situ Growth of Graphene Catalyzed by a Phase-Change Material at 400 °C for Wafer-Scale Optoelectronic Device Application

The use of metal foil catalysts in the chemical vapor deposition of graphene films makes graphene transfer an ineluctable part of graphene device fabrication, which greatly limits industrialization. Here, an oxide phase-change material (V₂O₅) is found to have the same catalytic effect on graphene growth as conventional metals. A uniform large-area graphene film can be obtained on a 10 nm V₂O₅ film. Density functional theory is used to quantitatively analyze the catalytic effect of V₂O₅. Due to the high resistance property of V₂O₅ at room temperature, the obtained graphene can be directly used in devices with V₂O₅ as an intercalation layer. A wafer-scale graphene-V₂O₅-Si (GVS) Schottky photodetector array is successfully fabricated. When illuminated by a 792 nm laser, the responsivity of the photodetector can reach 266 mA W⁻¹ at 0 V bias and 420 mA W⁻¹ at 2 V. The transfer-free device fabrication process enables high feasibility for industrialization.     

Tailoring the p-Band Center of N?S Pair for Accelerating High-Performance Lithium–Oxygen Battery

The local coordination environment of catalytical moieties directly determines the performance of electrochemical energy storage and conversion devices, such as Li–O₂ batteries (LOBs) cathode. However, understanding how the coordinative structure affects the performance, especially for non-metal system, is still insufficient. Herein, a strategy that introduces S-anion to tailor the electronic structure of nitrogen–carbon catalyst (SNC) is proposed to improve the LOBs performance. This study unveils that the introduced S-anion effectively manipulates the p-band center of pyridinic-N moiety, substantially reducing the battery overpotential by accelerating the generation and decomposition of intermediate products Li_1–3O₄. The lower adsorption energy of discharging product Li₂O₂ on N S pair accounts for the long-term cyclic stability by exposing the high active area under operation condition. This work demonstrates an encouraging strategy to enhance LOBs performance by modulating the p-band center on non-metal active sites.     

GaN薄膜的制备及其振动光谱的密度泛函理论研究

以氧化镓为镓源, 用溶胶-凝胶和高温氨化二步法, 在Si(111)衬底上制备出GaN薄膜. X射线衍射(XRD)分析表明制备的GaN薄膜是六角纤锌矿结构; 扫描电子显微镜(SEM)图片显示GaN晶粒的尺寸<100nm; 薄膜的红外光谱(FTIR)中有GaN的E1 (TO)声子模式. 用密度泛函理论(DFT)计算了氮化镓小团簇的振动频率. 结果表明: 富镓氮化镓团簇的振动频率在六方晶系纤锌矿结构GaN的光学声子峰值附近; 富氮氮化镓团簇中的N--N键的振动频率为2200cm^-1. 用氮化镓团簇的频谱对所制薄膜的红外光谱作了进一步分析.     

Atomically Dispersed Ni–N4 Sites Assist Pt3Ni Nanocages with Pt Skin to Synergistically Enhance Oxygen Reduction Activity and Stability

Currently, the rarity and high cost of platinum (Pt)-based electrocatalysts seriously limit their commercial application in fuel cells cathode. Decorating Pt with atomically dispersed metal–nitrogen sites possibly offers an effective pathway to synergy tailor their catalytic activity and stability. Here active and stable oxygen reduction reaction (ORR) electrocatalysts (Pt₃Ni@Ni–N₄–C) by in situ loading Pt₃Ni nanocages with Pt skin on single-atom nickel–nitrogen (Ni–N₄) embedded carbon supports are designed and constructed. The Pt₃Ni@Ni–N₄–C exhibits excellent mass activity (MA) of 1.92 A mg_Pt⁻¹ and specific activity of 2.65 mA cm_Pt⁻², together with superior durability of 10 mV decay in half-wave potential and only 2.1% loss in MA after 30 000 cycles. Theoretical calculations demonstrate that Ni–N₄ sites significant redistribute of electrons and make them transfer from both the adjacent carbon and Pt atoms to the Ni–N₄. The resultant electron accumulation region successfully anchored Pt₃Ni, that not only improves structural stability of the Pt₃Ni, but importantly makes the surface Pt more positive to weaken the adsorption of *OH to enhance ORR activity. This strategy lays the groundwork for the development of super effective and durable Pt-based ORR catalysts.     

Reconfiguring the Electronic Structure of Heteroatom Doped Carbon Supported Bimetallic Oxide@Metal Sulfide Core–Shell Heterostructure via In Situ Nb Incorporation toward Extrinsic Pseudocapacitor

High-energy-density battery-type materials have sparked considerable interest as supercapacitors electrode; however, their sluggish charge kinetics limits utilization of redox-active sites, resulting in poor electrochemical performance. Here, the unique core–shell architecture of metal organic framework derived N–S codoped carbon@Co_xS_y micropetals decorated with Nb-incorporated cobalt molybdate nanosheets (Nb-CMO₄@C_xS_yNC) is demonstrated. Coordination bonding across interfaces and π–π stacking interactions between CMO₄@C_xS_y and N and, S–C can prevent volume expansion during cycling. Density functional theory analysis reveals that the excellent interlayer and the interparticle conductivity imparted by Nb doping in heteroatoms synergistically alter the electronic states and offer more accessible species, leading to increased electrical conductivity with lower band gaps. Consequently, the optimized electrode has a high specific capacity of 276.3 mAh g⁻¹ at 1 A g⁻¹ and retains 98.7% of its capacity after 10 000 charge–discharge cycles. A flexible quasi-solid-state SC with a layer-by-layer deposited reduced graphene oxide /Ti₃C₂T_X anode achieves a specific energy of 75.5 Wh kg⁻¹ (volumetric energy of 1.58 mWh cm⁻³) at a specific power of 1.875 kWh kg⁻¹ with 96.2% capacity retention over 10 000 charge–discharge cycles.