Boosting Electrochemical Urea Synthesis via Constructing Ordered Pd–Zn Active Pair

Electrochemical co-reduction of nitrate(NO_(3)^(-))and carbon dioxide(CO_(2))has been widely regarded as a promising route to produce urea under ambient conditions,however the yield rate of urea has remained limited.Here,we report an atomically ordered intermetallic pallium-zinc(PdZn)electrocatalyst comprising a high density of PdZn pairs for boosting urea electrosynthesis.It is found that Pd and Zn are responsible for the adsorption and activation of NO_(3)^(-)and CO_(2),respectively,and thus the co-adsorption and co-activation NO_(3)^(-)and CO_(2) are achieved in ordered PdZn pairs.More importantly,the ordered and well-defined PdZn pairs provide a dual-site geometric structure conducive to the key C-N coupling with a low kinetical barrier,as demonstrated on both operando measurements and theoretical calculations.Consequently,the PdZn electrocatalyst displays excellent performance for the co-reduction to generate urea with a maximum urea Faradaic efficiency of 62.78%and a urea yield rate of 1274.42μg mg^(-1) h^(-1),and the latter is 1.5-fold larger than disordered pairs in PdZn alloys.This work paves new pathways to boost urea electrosynthesis via constructing ordered dual-metal pairs.

Building Fe atom–cluster composite sites using a site occupation strategy to boost electrochemical oxygen reduction

The high-temperature pyrolysis process for preparing M–N–C single-atom catalyst usually results in high heterogeneity in product structure concurrently contains multiscale metal phases from single atoms(SAs),atomic clusters to nanoparticles.Therefore,understanding the interactions among these components,especially the synergistic effects between single atomic sites and cluster sites,is crucial for improving the oxygen reduction reaction(ORR)activity of M–N–C catalysts.Accordingly,herein,we constructed a model catalyst composed of both atomically dispersed FeN4 SA sites and adjacent Fe clusters through a site occupation strategy.We found that the Fe clusters can optimize the adsorption strength of oxygen reduction intermediates on FeN4 SA sites by introducing electron-withdrawing–OH ligands and decreasing the d-band center of the Fe center.The as-developed catalyst exhibits encouraging ORR activity with halfwave potentials(E1/2)of 0.831 and 0.905 V in acidic and alkaline media,respectively.Moreover,the catalyst also represents excellent durability exceeding that of Fe–N–C SA catalyst.The practical application of Fe(Cd)–CNx catalyst is further validated by its superior activity and stability in a metalair battery device.Our work exhibits the great potential of synergistic effects between multiphase metal species for improvements of singleatom site catalysts.

Nitrogen and sulfur dual-doped high-surface-area hollow carbon nanospheres for efficient CO2 reduction

The electrochemical reduction of CO2(CO2 RR) can substantially contribute to the production of useful chemicals and reduction of global CO2 emissions. Herein, we presented N and S dual-doped high-surface-area carbon materials(SZ-HCN) as CO2 RR catalysts. N and S were doped by one-step pyrolysis of a N-containing polymer and S powder. ZnCl2 was applied as a volatile porogen to prepare porous SZ-HCN. SZ-HCN with a high specific surface area(1510 m2 g–1) exhibited efficient electrocatalytic activity and selectivity for CO2 RR. Electrochemical measurements demonstrated that SZ-HCN showed excellent catalytic performance for CO2-to-CO reduction with a high CO Faradaic efficiency(~93%) at-0.6 V. Furthermore, SZ-HCN offered a stable current density and high CO selectivity over at least 20 h continuous operation, revealing remarkable electrocatalytic durability. The experimental results and density functional theory calculations indicated that N and S dual-doped carbon materials required lower Gibbs free energy to form the COOH* intermediate than that for single-N-doped carbon for CO2-to-CO reduction, thereby enhancing CO2 RR activity.

Organic-inorganic hybrid hole transport layers with SnS doping boost the performance of perovskite solar cells

Perovskite solar cells(PSCs) have demonstrated excellent photovoltaic performance which currently rival the long-standing silicon solar cells’ efficiency. However, the relatively poor device operational stability of PSCs still limits their future commercialization. Binary sulfide is a category of materials with promising optoelectrical properties, which shows the potential to improve both the efficiency and stability of PSCs.Here we demonstrate that the inorganic tin monosulfide(Sn S) can be an efficient dopant in 2,2’,7,7’-tet rakis(N,N-di-p-methoxy-phenylamine)-9,9’-spirobifluorene(spiro-OMe TAD) to form a composite hole transport layer(HTL) for PSCs. Sn S nanoparticles(NPs) synthesized through a simple chemical precipitation method exhibit good crystallization and suitable band matching with the perovskites. The introduction of Sn S NPs in Spiro-OMTAD HTLs enhanced charge extraction, reduced trap state density, and shallowed trap state energy level of the devices based on the composite HTLs. Therefore, the resulting solar cells employing Sn S-doped spiro-OMe TAD HTLs delivered an improved stabilized power output efficiency of 21.75% as well as enhanced long-term stability and operational stability. Our results provide a simple method to modify the conventional spiro-OMe TAD and obtain PSCs with both high efficiency and good stability.

Construction of cobalt-copper bimetallic oxide heterogeneous nanotubes for high-efficient and low-overpotential electrochemical CO_(2) reduction

Currently,global warming and energy problems become more and more serious with the development of economy and the continuous consumption of fossil fuel,which are due to the release of greenhouse gas in the process of fossil fuel combustion and industrial manufacturing.

Accelerating lithium-sulfur battery reaction kinetics and inducing 3D deposition of Li_(2)S using interactions between Fe_(3)Se_(4)and lithium polysulfides

Although lithium-sulfur batteries(LSBs)exhibit high theoretical energy density,their practical application is hindered by poor conductivity of the sulfur cathode,the shuttle effect,and the irreversible deposition of Li_(2)S.To address these issues,a novel composite,using electrospinning technology,consisting of Fe_(3)Se_(4)and porous nitrogen-doped carbon nanofibers was designed for the interlayer of LSBs.The porous carbon nanofiber structure facilitates the transport of ions and electrons,while the Fe_(3)Se_(4)material adsorbs lithium polysulfides(LiPSs)and accelerates its catalytic conversion process.Furthermore,the Fe_(3)Se_(4)material interacts with soluble LiPSs to generate a new polysulfide intermediate,Li_(x)FeS_(y)complex,which changes the electrochemical reaction pathway and facilitates the three-dimensional deposition of Li_(2)S,enhancing the reversibility of LSBs.The designed LSB demonstrates a high specific capacity of1529.6 mA h g^(-1)in the first cycle at 0.2 C.The rate performance is also excellent,maintaining an ultra-high specific capacity of 779.7 mA h g^(-1)at a high rate of 8 C.This investigation explores the mechanism of the interaction between the interlayer and LiPSs,and provides a new strategy to regulate the reaction kinetics and Li_(2)S deposition in LSBs.

Recent advances in spinel-type electrocatalysts for bifunctional oxygen reduction and oxygen evolution reactions

The demand for efficient and environmentally-benign electrocatalysts that help availably harness the renewable energy resources is growing rapidly. In recent years, increasing insights into the design of water electrolysers, fuel cells, and metal–air batteries emerge in response to the need for developing sustainable energy carriers, in which the oxygen evolution reaction and the oxygen reduction reaction play key roles. However, both reactions suffer from sluggish kinetics that restricts the reactivity. Therefore, it is vital to probe into the structure of the catalysts to exploit high-performance bifunctional oxygen electrocatalysts. Spinel-type catalysts are a class of materials with advantages of versatility, low toxicity, low expense, high abundance, flexible ion arrangement, and multivalence structure. In this review, we afford a basic overview of spinel-type materials and then introduce the relevant theoretical principles for electrocatalytic activity, following that we shed light on the structure–property relationship strategies for spinel-type catalysts including electronic structure, microstructure, phase and composition regulation,and coupling with electrically conductive supports. We elaborate the relationship between structure and property, in order to provide some insights into the design of spinel-type bifunctional oxygen electrocatalysts.

A Multifunctional Anti-Proton Electrolyte for High-Rate and Super-Stable Aqueous Zn-Vanadium Oxide Battery

Large volumetric expansion of cathode hosts and sluggish transport kinetics in the cathode–electrolyte interface,as well as dendrite growth and hydrogen evolution at Zn anode side are considered as the system problems that cause the electrochemical failure of aqueous Zn-vanadium oxide battery.In this work,a multifunctional anti-proton electrolyte was proposed to synchronously solve all those issues.Theoretical and experimental studies confirm that PEG 400 additive can regulate the Zn^(2+) solvation structure and inhibit the ionization of free water molecules of the electrolyte.Then,smaller lattice expansion of vanadium oxide hosts and less associated by-product formation can be realized by using such electrolyte.Besides,such electrolyte is also beneficial to guide the uniform Zn deposition and suppress the side reaction of hydrogen evolution.Owing to the integrated synergetic modifica-tion,a high-rate and ultrastable aqueous Zn-V_(2)O_(3)/C battery can be constructed,which can remain a specific capacity of 222.8 m Ah g^(-1)after 6000 cycles at 5 A g^(-1),and 121.8 m Ah g^(-1) even after 18,000 cycles at 20 A g^(-1),respectively.Such“all-in-one”solution based on the electrolyte design provides a new strategy for developing high-performance aqueous Zn-ion battery.

A hierarchically structured tin-cobalt composite with an enhanced electronic effect for high-performance CO_(2) electroreduction in a wide potential range

Earth-abundant and nontoxic Sn-based materials have been regarded as promising catalysts for the electrochemical conversion of CO_(2)to C1 products,e.g.,CO and formate.However,it is still difficult for Snbased materials to obtain satisfactory performance at low-to-moderate overpotentials.Herein,a simple and facile electrospinning technique is utilized to prepare a composite of a bimetallic Sn-Co oxide/carbon matrix with a hollow nanotube structure(Sn Co-HNT).Sn Co-HNT can maintain>90%faradaic efficiencies for C1 products within a wide potential range from-0.6 VRHE to-1.2 VRHE,and a highest 94.1%selectivity towards CO in an H-type cell.Moreover,a 91.2%faradaic efficiency with a 241.3 m A cm^(-2)partial current density for C1 products could be achieved using a flow cell.According to theoretical calculations,the fusing of Sn/Co oxides on the carbon matrix accelerates electron transfer at the atomic level,causing electron deficiency of Sn centers and reversible variation between Co^(2+)and Co^(3+)centers.The synergistic effect of the Sn/Co composition improves the electron affinity of the catalyst surface,which is conducive to the adsorption and stabilization of key intermediates and eventually increases the catalytic activity in CO_(2)electroreduction.This study could provide a new strategy for the construction of oxide-derived catalysts for CO_(2)electroreduction.

Constructing hierarchical arrays with core-shell metal oxides@metal coordination polymers for efficient and stable overall water splitting

Developing non-precious metal-based bifunctional electrocatalysts capable for both hydrogen evolution reaction(HER)and oxygen evolution reaction(OER)is essential to achieve efficient water electrolysis for mass hydrogen production,however it remains challenging.Here,we report the synthesis of hierarchical nanorod arrays comprising core-shell structured P-doped NiMoO4@NiFe-coordination polymer(denoted as P-NiMoO4@NiFeCP)as bifunctional electrocatalysts for water electrolysis.Furthermore,we systematically investigate the influence of NiFeCP shell thickness on electrocatalytic activity,manifesting the presence of strong interfacial synergetic effect between P-NiMoO4 and NiFeCP for boosting both the HER and OER.With advantageous hierarchical architectures and unique core-shell structures,optimized P-NiMoO_(4)@NiFeCP-7.3(7.3 is the shell thickness in nm)requires overpotentials of merely 256 and 297 mV to yield a current density of 1000 mA·cm^(−2)for the HER and OER in 1 M KOH,respectively.More importantly,it can serve as a bifunctional electrocatalyst for efficient and sustainable overall water electrolysis,delivering large current densities of 500 and 1000 mA·cm^(−2)at low cell voltages of 1.804 and 1.865 V,along with high stability of over 500 h at 1000 mA·cm−2,demonstrating the great potential of this electrocatalyst towards practical applications.

Janus heterostructure of cobalt and iron oxide as dual-functional electrocatalysts for overall water splitting

In electrocatalytic water splitting,low-cost dual-functional catalysts can not only reduce costs but also avoid cross-contamination of cathode and anode.However,the orderly aggregation of active sites for hydrogen evolution reaction(HER)and oxygen evolution reaction(OER)into a specific catalyst is very challenging.In this study,a Co/Fe_(3)O_(4)Janus heterojunction supported on carbon fiber paper(J-CoFe-CFP)is designed and successfully synthesized.Generally,Co-Fe oxides have preferable OER activity but weak HER activity.However,in J-CoFe-CFP,due to the intense and special electronic interaction of different substances(Co and Fe3O4)in the Janus heterogeneous interface,a huge number of tidy high-quality HER and OER active sites are uniformly distributed on the interface simultaneously,which endows the catalyst with both excellent HER and OER performance.In HER,the overpotential@10 mA·cm^(−2)(ηHER)is only 53.9 mV,and the Tafel slope is 43.7 mV·dec^(−1).In OER,theηis 272 mV,and the Tafel slope is 50.2 mV·dec^(−1),much lower than those of RuO_(2)/CFP.In the J-CoFe-CFP||J-CoFe-CFP two-electrode system,the required voltage is only 1.26 V at the beginning and 1.56 V@10 mA·cm^(−2),much lower than those of RuO_(2)/CFP||20%Pt/C/CFP.This work provides a Janus heterojunction pathway for bifunctional water electrolysis catalysts.

Grain Boundaries Engineering of Hollow Copper Nanoparticles Enables Highly Efficient Ammonia Electrosynthesis from Nitrate

Electrochemical nitrate reduction reaction(NO_(3)−RR)is an ideal route to produce ammonia(NH_(3))under ambient conditions.Although a markedly improved NH3 production rate has been achieved on the NO_(3)−RR compared with the nitrogen reduction reaction(NRR),the NH_(3) production rate of NO_(3)−RR is still well below the industrial Haber-Bosch route due to the lack of robust electrocatalysts for yielding high current densitieswith concurrently good suppression of hydrogen evolution reaction(HER).Herein,we describe an in situ electrochemical strategy for the synthesis of hollow carbon-coated Cu nanoparticles(NPs)(HSCu@C)with abundant grain boundaries(HSCu-AGB@C)for highly efficient NO_(3)−RR in both alkaline and neutral media.Impressively,in alkaline media,the HSCu-AGB@C can achieve a maximum NH3 Faradaic efficiency of 94.2% with an ultrahigh NH_(3) rate of 487.8 mmol g^(−1) cat h^(−1) at−0.2 V versus a reversible hydrogen electrode,more than 2.4-fold of the rate obtained in the Haber-Bosch.Both theoretic computations and experimental results uncover that the grain boundaries play the key to improve the NO_(3)−RR performance.Herein,the industrial-scale NH_(3) production ratemay open exciting opportunities for the practical electrosynthesis NH_(3) under ambient conditions.

Unconventional chemical graphitization and functionalization of graphene oxide toward nanocomposites by degradation of ZnSe[DETA]0.5 hybrid nanobelts

The high surface energy of nanomaterials endows them a metastable nature,which greatly limits their application.However,in some cases,the degradation process derived from the poor stability of nanomaterials offers an unconventional approach to design and obtain functional nanomaterials.Herein,based on the poor stability of ZnSe-[DETA]0.5 hybrid nanobelts,we developed a new strategy to chemically graphitize and functionalize graphene oxide(GO).When ZnSe[DETA]0.5 hybrid nanobelts encountered a strong acid,they were attacked by H^+cations and could release highly reactive Se^2−anions into the reaction solution.Like other common reductants(such as N2H4·H2O),these Se^2−anions exhibited an excellent ability to restore the structure of GO.The structural restoration of GO was greatly affected by the reaction time,the volume of HCl,and the mass ratio between GO and ZnSe[DETA]0.5 nanobelts.By carefully controlling the reaction process and the post-processing process,we finally obtained several Se-based reduced GO(RGO)nanocomposites(such as ZnSe/Se-RGO,ZnSe-RGO,and Se-RGO)and various selenide/metal-RGO nanocomposites(such as Ag2Se-RGO,Cu2Se-RGO,and Pt-RGO).Although the original structure and composition of ZnSe[DETA]0.5 nanobelts are destroyed,the procedure presents an unconventional way to chemically graphitize and functionalize GO and thus provides a new material synthesis platform for nanocomposites.

Electronic structure and geometric construction modulation of carbon-based single/dual atom catalysts for electrocatalysis

Both carbon-based single atom catalysts(SACs)and dual atom catalysts(DACs)have garnered significant attention in the field of electrochemical reactions because of the impressive attributes,including exceptional catalytic activity,selectivity,and cost-effectiveness.The ability to modulate the electronic structure and geometric construction of active sites within SACs/DACs is paramount for unleashing their complete potential,which in turn can ultimately dictate catalytic behavior with unprecedented precision.In this review,the recent major developments of the regulation strategies for modulating electronic structure and geometric construction of carbon-based SACs/DACs are summarized.For the SACs,the recently reported modulation methods are categorized into four strategies,including adjusting the density of single atoms,defect engineering,confinement effect and strain engineering.And for the DACs,the five methods contain bonded dual-atom adjustment,non-bonded and bridged dual-atom adjustment,metal and nonmetal dual-atom adjustment,bilayer dual-atom adjustment and homogeneous dual-atom adjustment.The recently developed synthetic strategies are comprehensively summarized,especially their electronic structure and geometric configuration are discussed in detail,the different catalytic applications of electrochemical reactions,and their unique catalytic mechanism are highlighted.Finally,the challenges and prospects of SACs/DACs for tailoring their electronic structures and geometric arrangements are further discussed.

Efficient reversible CO/CO_(2) conversion in solid oxide cells with a phase-transformed fuel electrode

The reversible solid oxide cell(RSOC)is an attractive technology to mutually convert power and chemicals at elevated temperatures.However,its development has been hindered mainly due to the absence of a highly active and durable fuel electrode.Here,we report a phase-transformed CoFe-Sr_(3)Fe_(1.25)Mo_(0.75)O_(7)-δ(CoFe-SFM)fuel electrode consisting of CoFe nanoparticles and Ruddlesden-Popper-layered Sr_(3)Fe_(1.25)Mo_(0.75)O_(7)-δ(SFM)from a Sr_(2)Fe_(7/6)Mo_(0.5)Co_(1/3)O_(6)-δ(SFMCo)perovskite oxide after annealing in hydrogen and apply it to reversible CO/CO_(2)conversion in RSOC.The CoFeSFM fuel electrode shows improved catalytic activity by accelerating oxygen diffusion and surface kinetics towards the CO/CO_(2)conversion as demonstrated by the distribution of relaxation time(DRT)study and equivalent circuit model fitting analysis.Furthermore,an electrolyte-supported single cell is evaluated in the 2:1 CO-CO_(2)atmosphere at 800℃,which shows a peak power density of 259 mW cm^(-2)for CO oxidation and a current density of-0.453 A cm^(-2)at 1.3 V for CO_(2)reduction,which correspond to 3.079 and3.155 m L min-1cm^(-2)for the CO and CO_(2)conversion rates,respectively.More importantly,the reversible conversion is successfully demonstrated over 20 cyclic electrolysis and fuel cell switching test modes at 1.3 and 0.6 V.This work provides a useful guideline for designing a fuel electrode through a surface/interface exsolution process for RSOC towards efficient CO-CO_(2)reversible conversion.

Fluorine-induced dual defects in NiP_(2) anode with robust sodium storage performance

Metal phosphides have shown great application potential as anode for sodium-ion batteries(NIBs)owing to high theoretical capacity,suitable operation voltage and abundant resource.Unfortunately,the application of NiP_(2) anode is severely impeded by low practical capacity and fast capacity decay due to the huge volume variation and low reactivity of internal phosphorus(P)component towards Na^(+).Herein,electronic structure modulation of NiP_(2) via heteroatoms doping and introducing vacancies defects to enhance Na+adsorption sites and diffusion kinetics is successfully attempted.The as-synthesized three-dimensional(3D)bicontinuous carbon matrix decorated with well-dispersed fluorine(F)-doped NiP_(2) nanoparticles(F-NiP_(2)@carbon nanosheets)delivers a high reversible capacity(585 mAh·g^(−1) at 0.1 A·g^(−1))and excellent long cycling stability(244 mAh·g^(−1) over 1,000 cycles at 2 A·g^(−1))when tested as anode in NIBs.Density functional theory(DFT)calculations reveal that F doping in NiP_(2) induces the formation of P vacancies with increased Na+adsorption energy and accelerates the alloying of internal P component.The F-NiP_(2)@carbon nanosheets//Na_(3)V_(2)(PO_(4))_(3) full cell is evaluated showing stable long cycling life.The heteroatoms doping-induced dual defects strategy opens up a new way of metal phosphides for sodium storage.

Bimetallic two-dimensional materials for electrocatalytic oxygen evolution

Electrocatalytic oxygen evolution reaction(OER)is one of the important half reactions of electrocatalytic water splitting.However,the slow kinetic process involving four-electron transfer severely limits its reaction efficiency,which in turn limits the overall electrocatalytic hydrolysis efficiency.In order to improve the activity of the electrocatalytic OER,researchers mainly update the catalyst from three aspects,that is,increase the conductivity of the electrocatalyst,and the quantity and quality of active sites.Twodimensional(2 D)engineering can effectively reduce the resistance of the materials and greatly increase the number of electrochemically active sites,while heterometal doping,or the bimetal strategy,can improve the quality of active sites via changing the electronic structure of the material.Thus,the combination of the two can enhance the activity of electrocatalytic OER in all three aspects:conductivity,number and quality of active sites.However,there is currently no review on this topic.Therefore,in this review,we summarize the application of bimetallic 2 D materials in electrocatalytic OER from four aspects:the structure,synthesis strategy,catalytic efficiency,and reaction mechanism.

Pyrimidine donor induced built-in electric field between melon chains in crystalline carbon nitride to facilitate excitons dissociation

The strong intrinsic Coulomb interactions of Frenkel excitons in crystalline carbon nitride(CCN) greatly limits their dissociation into electrons and holes, resulting in unsatisfactory charges separation and photocatalytic efficiency. Herein, we propose a strategy to facilitate excitons dissociation by molecular regulation induced built-in electric field(BIEF). The electron-rich pyrimidine-ring into CCN changes the charge density distribution over heptazine-rings to induce BIEF between melon chains. Such BIEF is sufficient to overcome the considerable exciton binding energy(EBE) and reduce it from 38.4 meV to 16.4 meV,increasing the excitons dissociation efficiency(EDE) from 21.5% to 51.9%. Our results establish a strategy to facilitate excitons dissociation through molecular regulation induced BIEF, targeting the intrinsic high EBE and low EDE of polymer photocatalysts.

Support effect and confinement effect of porous carbon loaded tin dioxide nanoparticles in high-performance CO_(2) electroreduction towards formate

Leveraging the interplay between the metal component and the supporting material represents a cornerstone strategy for augmenting electrocatalytic efficiency,e.g.,electrocatalytic CO_(2)reduction reaction(CO_(2)RR).Herein,we employ freestanding porous carbon fibers(PCNF)as an efficacious and stable support for the uniformly distributed SnO_(2)nanoparticles(SnO_(2)PCNF),thereby capitalizing on the synergistic support effect that arises from their strong interaction.On one hand,the interaction between the SnO_(2)nanoparticles and the carbon support optimizes the electronic configuration of the active centers.This interaction leads to a noteworthy shift of the d-band center toward stronger intermediate adsorption energy,consequently lowering the energy barrier associated with CO_(2)reduction.As a result,the Sn O_(2)PCNF realizes a remarkable CO_(2)RR performance with excellent selectivity towards formate(98.1%).On the other hand,the porous carbon fibers enable the uniform and stable dispersion of SnO_(2)nanoparticles,and this superior porous structure of carbon supports can also facilitate the exposure of the SnO_(2)nanoparticles on the reaction interface to a great extent.Consequently,adequate contact between active sites,reactants,and electrolytes can significantly increase the metal utilization,eventually bringing forth a remarkable7.09 A/mg mass activity.This work might provide a useful idea for improving the utilization rate of metals in numerous electrocatalytic reactions.