查看更多>>摘要：The Fe-N-C material represents an attractive oxygen reduction reaction electrocatalyst,and the FeN4 moiety has been identified as a very competitive catalytic active site.Fine tuning of the coordination structure of FeN4 has an essential impact on the catalytic performance.Herein,we construct a sulfur-modified Fe-N-C catalyst with controllable local coordination environment,where the Fe is coordinated with four in-plane N and an axial external S.The external S atom affects not only the electron distribution but also the spin state of Fe in the FeN4 active site.The appearance of higher valence states and spin states for Fe demonstrates the increase in unpaired electrons.With the above characteristics,the adsorption and desorption of the reactants at FeN4 active sites are optimized,thus promoting the oxygen reduction reaction activity.This work explores the key point in electronic configuration and coordination environment tuning of FeN4 through S doping and provides new insight into the construction of M-N-C-based oxygen reduction reaction catalysts.
查看更多>>摘要：The emerging of single-atom catalysts(SACs)offers a great opportunity for the development of advanced energy storage and conversion devices due to their excellent activity and durability,but the actual mass production of high-loading SACs is still challenging.Herein,a facile and green boron acid(H3BO3)-assisted pyrolysis strategy is put forward to synthesize SACs by only using chitosan,cobalt salt and H3BO3 as precursor,and the effect of H3BO3 is deeply investigated.The results show that molten boron oxide derived from H3BO3 as ideal high-temperature carbonization media and blocking media play important role in the synthesis process.As a result,the acquired Co/N/B tri-doped porous carbon framework(Co-N-B-C)not only presents hierarchical porous structure,large specific surface area and abundant carbon edges but also possesses high-loading single Co atom(4.2 wt.％),thus giving rise to outstanding oxygen catalytic performance.When employed as a catalyst for air cathode in Zn-air batteries,the resultant Co-N-B-C catalyst shows remarkable power density and long-term stability.Clearly,our work gains deep insight into the role of H3BO3 and provides a new avenue to synthesis of high-performance SACs.
查看更多>>摘要：Owing to the intrinsically sluggish kinetics of urea oxidation reaction(UOR)involving a six-electron transfer process,developing efficient UOR electrocatalyst is a great challenge remained to be overwhelmed.Herein,by taking advantage of 2-Methylimidazole,of which is a kind of alkali in water and owns strong coordination ability to Co2+in methanol,trace Co(1.0 mol％)addition was found to induce defect engineering on α-Ni(OH)2 in a dual-solvent system of water and methanol.Physical characterization results revealed that the synthesized electrocatalyst(WM-Ni0.99Co0.01(OH)2)was a kind of defective nanosheet with thickness around 5-6 nm,attributing to the synergistic effect of Co doping and defect engineering,its electron structure was finely altered,and its specific surface area was tremendously enlarged from 68 to 172.3 m2 g-1.With all these merits,its overpotential to drive 10 mA cm-2 was reduced by 110 mV.Besides,the interfacial behavior of UOR was also well deciphered by operando electrochemical impedance spectroscopy.
查看更多>>摘要：The rational design of metal single-atom catalysts(SACs)for electrochemical nitrogen reduction reaction(NRR)is challenging.Two-dimensional metal-organic frameworks(2DMOFs)is a unique class of promising SACs.Up to now,the roles of individual metals,coordination atoms,and their synergy effect on the electroanalytic performance remain unclear.Therefore,in this work,a series of 2DMOFs with different metals and coordinating atoms are systematically investigated as electrocatalysts for ammonia synthesis using density functional theory calculations.For a specific metal,a proper metal-intermediate atoms p-d orbital hybridization interaction strength is found to be a key indicator for their NRR catalytic activities.The hybridization interaction strength can be quantitatively described with the p-/d-band center energy difference(Δd-p),which is found to be a sufficient descriptor for both the p-d hybridization strength and the NRR performance.The maximum free energy change(ΔGmax)and Δd-p have a volcanic relationship with OsC4(Se)4 located at the apex of the volcanic curve,showing the best NRR performance.The asymmetrical coordination environment could regulate the band structure subtly in terms of band overlap and positions.This work may shed new light on the application of orbital engineering in electrocatalytic NRR activity and especially promotes the rational design for SACs.
查看更多>>摘要：Dendritic mesoporous silica nanoparticles own three-dimensional center-radial channels and hierarchical pores,which endows themselves with super-high specific surface area,extremely large pore volumes,especially accessible internal spaces,and so forth.Dissimilar guest species(such as organic groups or metal nanoparticles)could be readily decorated onto the interfaces of the channels and pores,realizing the functionalization of dendritic mesoporous silica nanoparticles for targeted applications.As adsorbents and catalysts,dendritic mesoporous silica nanoparticles-based materials have experienced nonignorable development in CO2 capture and catalytic conversion.This comprehensive review provides a critical survey on this pregnant subject,summarizing the designed construction of novel dendritic mesoporous silica nanoparticles-based materials,the involved chemical reactions(such as CO2 methanation,dry reforming of CH4),the value-added chemicals from CO2(such as cyclic carbonates,2-oxazolidinones,quinazoline-2,4(1H,3H)-diones),and so on.The adsorptive and catalytic performances have been compared with traditional silica mesoporous materials(such as SBA-15 or MCM-41),and the corresponding reaction mechanisms have been thoroughly revealed.It is sincerely expected that the in-depth discussion could give materials scientists certain inspiration to design brand-new dendritic mesoporous silica nanoparticles-based materials with superior capabilities towards CO2 capture,utilization,and storage.
查看更多>>摘要：Developing stable and efficient nonprecious-metal-based oxygen evolution catalysts in the neutral electrolyte is a challenging but essential goal for various electrochemical systems.Particularly,cobalt-based spinels have drawn a considerable amount of attention but most of them operate in alkali solutions.However,the frequently studied Co-Fe spinel system never exhibits appreciable stability in nonbasic conditions,not to mention attract further investigation on its key structural motif and transition states for activity loss.Herein,we report exceptional stable Co-Fe spinel oxygen evolution catalysts(～30％Fe is optimal)in a neutral electrolyte,owing to its unique metal ion arrangements in the crystal lattice.The introduced iron content enters both the octahedral and tetrahedral sites of the spinel as Fe2+and Fe3+(with Co ions having mixed distribution as well).Combining density functional theory calculations,we find that the introduction of Fe to Co3O4 lowers the covalency of metal-oxygen bonds and can help suppress the oxidation of Co2+/3+and 02-.It implies that the Co-Fe spinel will have minor surface reconstruction and less lattice oxygen loss during the oxygen evolution reaction process in comparison with Co3O4 and hence show much better stability.These findings suggest that there is still much chance for the spinel structures,especially using reasonable sublattices engineering via multimetal doping to develop advanced oxygen evolution catalysts.
查看更多>>摘要：Exploring noble metal-free catalyst materials for high efficient electrochemical water splitting to produce hydrogen is strongly desired for renewable energy development.In this article,a novel bifunctional catalytic electrode of insitu-grown type for alkaline water splitting based on FeCoNi alloy substrate has been successfully prepared via a facile one-step hydrothermal oxidation route in an alkaline hydrogen peroxide medium.It shows that the matrix alloy with the atom ratio 4∶3∶3 of Fe∶Co∶Ni can obtain the best catalytic performance when hydrothermally treated at 180℃ for 18 h in the solution containing 1.8 M hydrogen peroxide and 3.6 M sodium hydroxide.The as-prepared Fe0.4Co0.3Ni0.3-1.8 electrode exhibits small overpotentials of only 184 and 175 mV at electrolysis current density of 10 mA cm-2 for alkaline OER and HER processes,respectively.The overall water splitting at electrolysis current density of 10 mA cm-2 can be stably delivered at a low cell voltage of 1.62 V.These characteristics including the large specific surface area,the high surface nickel content,the abundant catalyst species,the balanced distribution between bivalent and trivalent metal ions,and the strong binding of in-situ naturally growed catalytic layer to matrix are responsible for the prominent catalytic performance of the Fe0.4Co0.3Ni0.3-1.8 electrode,which can act as a possible replacement for expensive noble metal-based materials.
查看更多>>摘要：The rhombohedral α-GeTe can be approximated as a slightly distorted rock-salt structure along its[1 1 1]direction and possesses superb thermoelectric performance.However,the role of such a ferroelectric-like structural distortion on its transport properties remains unclear.Herein,we performed a systematic study on the crystal structure and electronic band structure evolutions of Ge1-xSnxTe alloys where the degree of ferroelectric distortion is continuously tuned.It is revealed that the band gap is maximized while multiple valence bands are converged at x=0.6,where the ferroelectric distortion is the least but still works.Once undistorted,the band gap is considerably reduced,and the valence bands are largely separated again.Moreover,near the ferro-to-paraelectric phase transition Curie temperature,the lattice thermal conductivity reaches its minima because of significant lattice softening enabled by ferroelectric instability.We predict a peak ZT value of 2.6 at 673 K in α-GeTe by use of proper dopants which are powerful in suppressing the excess hole concentrations but meanwhile exert little influence on the ferroelectric distortion.
查看更多>>摘要：Thermoelectric power generators have attracted increasing interest in recent years owing to their great potential in wearable electronics power supply.It is noted that thermoelectric power generators are easy to damage in the dynamic service process,resulting in the formation of microcracks and performance degradation.Herein,we prepare a new hybrid hydrogel thermoelectric material PAAc/XG/Bi2Se0.3Te2.7 by an in situ polymerization method,which shows a high stretchable and self-healable performance,as well as a good thermoelectric performance.For the sample with Bi2Se0.3Te2.7 content of 1.5 wt％(i.e.,PAAc/XG/Bi2Se0.3Te27(1.5 wt％)),which has a room temperature Seebeck coefficient of-0.45 mV K-1,and exhibits an open-circuit voltage of-17.91 mV and output power of 38.1 nW at a temperature difference of 40 K.After being completely cut off,the hybrid thermoelectric hydrogel automatically recovers its electrical characteristics within a response time of 2.0 s,and the healed hydrogel remains more than 99％of its initial power output.Such stretchable and self-healable hybrid hydrogel thermoelectric materials show promising potential for application in dynamic service conditions,such as wearable electronics.
查看更多>>摘要：Myocardial damage resulting from acute myocardial infarction often leads to progressive heart failure and sudden death,highlighting the urgent clinical need for effective therapies.Recently,tanshinone ⅡA has been identified as a promising therapeutic agent for myocardial infarction.However,efficient delivery remains a major issue that limits clinical translation.To address this problem,an injectable thermosensitive poly(lactic acid-co-glycolic acid)-block-poly(ethylene glycol)-block-poly(lactic acid-co-glycolic acid)gel(PLGA-PEG-PLGA)system encapsulating tanshinone ⅡA-loaded reactive oxygen species-sensitive microspheres(Gel-MS/tanshinone ⅡA)has been designed and synthesized in this study.The thermosensitive hydrogel exhibits good mechanical properties after reaching body temperature.Microspheres initially immobilized by the gel exhibit excellent reactive oxygen species-triggered release properties in a high-reactive oxygen species environment after myocardial infarction onset.As a result,encapsulated tanshinone ⅡA is effectively released into the infarcted myocardium,where it exerts local anti-pyroptotic and anti-inflammatory effects.Importantly,the combined advantages of this technique contribute to the mitigation of left ventricular remodeling and the restoration of cardiac function following tanshinone ⅡA.Therefore,this novel,precision-guided intra-tissue therapeutic system allows for customized local release of tanshinone ⅡA,presenting a promising alternative treatment strategy aimed at inducing beneficial ventricular remodeling in the post-infarct heart.
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