Electronic modulation of two-dimensional bismuth-based nanosheets for electrocatalytic CO_(2) reduction to formate: A review

Electrocatalytic CO_(2) reduction reaction(eCO_(2) RR)has significant relevance to settle the global energy crisis and abnormal climate problem via mitigating the excess emission of waste CO_(2) and producing high-value-added chemicals.Currently,eCO_(2) RR to formic acid or formate is one of the most technologically and economically viable approaches to realize high-efficiency CO_(2) utilization,and the development of efficient electrocatalysts is very urgent to achieve efficient and stable catalytic performance.In this review,the recent advances for two-dimensional bismuth-based nanosheets(2D Bi-based NSs)electrocatalysts are concluded from both theoretical and experimental perspectives.Firstly,the preparation strategies of 2D Bi-based NSs in aspects to precisely control the thickness and uniformity are summarized.In addition,the electronic regulation strategies of 2D Bi-based NSs are highlighted to gain insight into the effects of the structure-property relationship on facilitating CO_(2) activation,improving product selectivity,and optimizing carrier transport dynamics.Finally,the considerable challenges and opportunities of 2D Bi-based NSs are discussed to lighten new directions for future research of eCO_(2) RR.

A high‐performance transition‐metal phosphide electrocatalyst for converting solar energy into hydrogen at 19.6% STH efficiency

The construction of high-efficiency and low-cost non-noble metal bifunctional electrocatalysts for water electrolysis is crucial for commercial large-scale application of hydrogen energy.Here,we report a novel strategy with erbiumdoped NiCoP nanowire arrays in situ grown on conductive nickel foam(Er-NiCoP/NF).Significantly,the developed electrode shows exceptional bifunctional catalytic activity,which only requires overpotentials of 46 and 225 mV to afford a current density of 10 mAcm^(−2) for the hydrogen evolution reaction(HER)and the oxygen evolution reaction(OER),respectively.Density functional theory calculations reveal that the appropriate Er incorporation into the NiCoP lattice can significantly modulate the electronic structure with the d-band centers of Ni and Co atoms by shifting to lower energies with respect to the Fermi level,and optimize the Gibbs free energies of HER/OER intermediates,thereby accelerating water-splitting kinetics.When assembled as a solar-driven overall water-splitting electrolyzer,the as-prepared electrode shows a high and stable solar-to-hydrogen efficiency of 19.6%,indicating its potential for practical storage of intermittent energy.

Charge-transfer-regulated bimetal ferrocene-based organic frameworks for promoting electrocatalytic oxygen evolution

The ferrocene(Fc)-based metal-organic frameworks(MOFs)are regarded as compelling platforms for the construction of efficient and robust oxygen evolution reaction(OER)electrocatalysts due to their superior conductivity and flexible electronic structure.Herein,density functional theory simulations were addressed to predict the electronic structure regulations of CoFc-MOF by nickel doping,which demonstrated that the well-proposed CoNiFc-MOFs delivered a small energy barrier,promoted conductivity,and well-regulated d-band center.Inspired by these,a series of sea-urchin-like CoNiFc-MOFs were successfully synthesized via a facile solvothermal method.Moreover,the synchrotron X-ray and X-ray photoelectron spectroscopy measurements manifested that the introduction of nickel could tailor the electronic structure of the catalyst and induce the directional transfer of electrons,thus optimizing the rate-determining step of^(*)O→^(*)OOH during the OER process and yielding decent overpotentials of 209 and 252 mV at 10 and 200 mA cm^(−2),respectively,with a small Tafel slope of 39 mV dec^(−1).This work presents a new paradigm for developing highly efficient and durable MOF-based electrocatalysts for OER.

Anomalous metastable hcp Ni nanocatalyst induced by non-metal N doping enables promoted ammonia borane dehydrogenation

Developing high-performing non-noble transition metal catalysts for H_(2) evolution from chemical hydrogen storage materials is of great significance for the hydrogen economy system, yet challenging. Herein,we present for the first time that anomalous metastable hexagonal close-packed Ni nanoparticles induced by heteroatom N doping encapsulated in carbon(N-hcp-Ni/C) can exhibit admirable catalytic performance for ammonia borane(AB) dehydrogenation, prominently outperforming conventional fcc Ni counterpart with similar morphology and favorably presenting the state-of-the-art level.Comprehensive experimental and theoretical studies unravel that unusual hcp phase engineering of Ni together with N doping could induce charge redistribution and modulate electronic structure, thereby facilitating H_(2)O adsorption and expediting H_(2)O dissociation(rate-determining step). As a result, AB dehydrogenation can be substantially boosted with the assistance of N-hcp-Ni/C. Our proposed strategy highlights that unconventional crystal phase engineering coupled with non-metal heteroatom doping is a promising avenue to construct advanced transition metal catalysts for future renewable energy technologies.

In situ confined vertical growth of Co_(2.5)Ni_(0.5)Si_(2)O_(5)(OH)_(4)nanoarrays on rGO for an efficient oxygen evolution reaction

Rational design of oxygen evolution reaction(OER)catalysts at low cost would greatly benefit the economy.Taking advantage of earth-abundant elements Si,Co and Ni,we produce a unique-structure where cobalt-nickel silicate hydroxide[Co_(2.5)Ni_(0.5)Si_(2)O_(5)(OH)_(4)]is vertically grown on a reduced graphene oxide(rGO)support(CNS@rGO).This is developed as a low-cost and prospective OER catalyst.Compared to cobalt or nickel silicate hydroxide@rGO(CS@rGO and NS@rGO,respectively)nanoarrays,the bimetal CNS@rGO nanoarray exhibits impressive OER performance with an overpotential of 307 mV@10 mA cm^(-2).This value is higher than that of CS@rGO and NS@rGO.The CNS@rGO nanoarray has an overpotential of 446 mV@100 mA cm^(-2),about 1.4 times that of the commercial RuO_(2)electrocatalyst.The achieved OER activity is superior to the state-of-the-art metal oxides/hydroxides and their derivatives.The vertically grown nanostructure and optimized metal-support electronic interactions play an indispensable role for OER performance improvement,including a fast electron transfer pathway,short proton/electron diffusion distance,more active metal centers,as well as optimized dualatomic electron density.Taking advantage of interlay chemical regulation and the in-situ growth method,the advanced-structural CNS@rGO nanoarrays provide a new horizon to the rational and flexible design of efficient and promising OER electrocatalysts.

Electronic regulation to achieve efficient anaerobic digestion of organic fraction of municipal solid waste(OFMSW):strategies,challenges and potential solutions

Anaerobic digestion(AD)of organic fraction of municipal solid waste(OFMSW)is prone to system breakdown under high organic loading rates(OLRs)condition,which subsequently reduces the efficiency of digestion process and results in substantial economic losses.In this perspective paper,the substances metabolisms,electrons flow,as well as microbial interaction mechanisms within AD process are comprehensively discussed,and the underlying bottleneck that causes inefficient methane production is identified,which is“electrons surplus”.Systems encountering severe electron surplus are at risk of process failure,making it crucial to proactively prevent this phenomenon through appropriate approaches.On this basis,the present perspective proposes three potential electronic regulation strategies to prevent electrons surplus,namely,electron shunt,accelerating electron transfer and regulating methanogenic metabolism pathway,and presents specific methodologies for each strategy.Furthermore,the potential solutions to challenges that may occur during the electronic regulation process are also presented in this paper.This perspective aims to provide innovative approaches to achieve the efficient and stable operation of OFMSW anaerobic digestion,especially under high OLRs condition.

Electronic structural engineering of bimetallic Bi-Cu alloying nanosheet for highly-efficient CO_(2) electroreduction and Zn-CO_(2) batteries

Regulating the electronic structure of Bi-based materials by alloying engineering is promising to promote the electrocatalytic activity,but it remains some challenges to be solved.In this study,a facile electrochemical co-deposition strategy is developed to synthesize the bimetallic Bi_(9)Cu_(1) alloy nanosheet on carbon cloth(Bi_(9)Cu_(1)/CC),which represents a novel self-supporting electrode for the electrocatalytic carbon dioxide(CO_(2))reduction reaction(CO_(2)RR).The Bi_(9)Cu_(1)/CC catalyst has achieved a remarkable catalytic performance with high Faradaic efficiencies(FE)of over 90%for formate at wide potentials from-0.7 to-1.2 V vs.reversible hydrogen electrode(RHE).Moreover,the reversible Zn-CO_(2) battery can be driven by Bi_(9)Cu_(1)/CC cathode with a largest power density of 1.4 mW·cm^(-2),and superior operating stability.The systematic characterizations and electrochemical results confirm that the improved catalytic active sites,the enhanced mass/charge transport and the optimal reaction kinetics of Bi nanosheet are realized for CO_(2)RR by Cu alloying.In situ attenuated total reflection infrared(ATR-IR)result confirms the bimetallic Bi-Cu active sites prefer to follow the^(*)OCHO conversion pathway.The density functional theory(DFT)calculations suggest that the Cu alloying contributes to the increased density of states near the Fermi surface of Bi and the optimized adsorption of^(*)OCHO intermediates on the Bi sites,resulting in the excellent catalytic performance.

Electronic structure regulation and built-in electric field synergistically strengthen photocatalytic nitrogen fixation performance on Ti-BiOBr/TiO_(2)heterostructure

At present,industrial synthetic ammonia was still obtained through the Hubble-Bosch process,with large energy consumption.It is a research hotspot to realize green synthetic ammonia by using solar energy.The difficulty of photocatalytic ammonia synthesis was that the photo-excited electrons have not enough energy to active N≡N.In this study,Ti was doped into BiOBr by one-step hydrothermal method,which was oxidized into TiO_(2)when the doping amount reaches the maximum,in situ forming Ti_(0.31)B_(0.69)OB/TiO_(2)composites.Benefiting from the synergistic effect of Ti doping and S-scheme heterojunction,the synthetic ammonia efficiency of Ti_(0.31)B_(0.69)OB/TiO_(2)-11.96 reached 1.643 mmol·g_(cat)^(-1)at mild conditions and without hole scavenger for up to 7 h,the efficiency of synthetic ammonia is 115 times,10.5 times and 3.3 times of that of BiOBr,Ti_(0.31)B_(0.69)OB and TiO_(2),respectively.Specifically,DFT calculation confirms that Ti doping accurately refine the electronic structure of BiOBr,facilitate nitrogen adsorption activation and reduce hydrogenation reaction energy barrier,thus accelerating the reaction kinetics of photocatalytic nitrogen reduction(NRR),Meanwhile,constructing S-scheme heterojunction boosts the separation and transfer of photogenerated electron-hole pairs,improving the reduction ability of electrons in the conduction band of TiO_(2)and the oxidation ability of holes in the valence band of Ti_(0.31)B_(0.69)OB.

Modulate the electronic structure of Cu_(7)S_(4)nanosheet on TiO_(2)for enhanced photocatalytic hydrogen evolution

TiO_(2)is a promising photocatalyst due to its high thermodynamic stability and non-toxicity.However,its applications have been still limited because of the high recombination rate of electron-hole pairs.Herein,we show that by combining heterojunction construction and electronic structure regulation,the electron-hole pairs in TiO_(2)can be effectively separated for enhanced photocatalytic hydrogen evolution.The optimized Cu_(7)S_(4)nanosheet decorated TiO_(2)achieves much enhanced H_(2)evolution rate(11.5 mmol·g−1·h−1),which is 13.8 and 4.2 times of that of TiO_(2)and Cu_(7)S_(4)/TiO_(2),respectively.The results of photoluminescence spectroscopy,transient photocurrent spectra,ultraviolet-visible diffuse reflectance spectra,and electrochemical impedance spectroscopy collectively demonstrate that the enhanced photocatalytic performance of Air-Cu_(7)S_(4)/TiO_(2)is attributed to the effective separation of charge carriers and widened photoresponse range.The electron paramagnetic resonance and X-ray photoelectron spectroscopy results indicate that the increase of Cu2+in the Cu_(7)S_(4)nanosheet after calcination can promote the charge transfer.This work provides an effective method to improve the electron migration rate and charge separation of TiO_(2),which holds great significance for being extended to other material systems and beyond.

Regulating electronic structure of CoN_(4)with axial Co-S for promoting oxygen reduction and Zn-air battery performance

Regulating the coordination environment of transition-metal based materials in the axial direction with heteroatoms has shown great potential in boosting the oxygen reduction reaction(ORR).The coordination configuration and the regulation method are pivotal and elusive.Here,we report a combined strategy of matrix-activization and controlled-induction to modify the CoN_(4)site by axial coordination of Co-S(Co1N_(4)-S_(1)),which was validated by the aberration-corrected electron microscopy and X-ray absorption fine structure analysis.The optimal Co1N_(4)-S_(1)exhibits an excellent alkaline ORR activity,according to the half-wave potential(0.897 V vs.reversible hydrogen electrode(RHE)),Tafel slope(24.67 mV/dec),and kinetic current density.Moreover,the Co1N_(4)-S_(1)based Zn-air battery displays a high power density of 187.55 mW/cm^(2)and an outstanding charge-discharge cycling stability for 160 h,demonstrating the promising application potential.Theoretical calculations indicate that the better regulation of CoN_(4)on electronic structure and thus the highly efficient ORR performance can be achieved by axial Co-S.

Regulating carbon work function to boost electrocatalytic activity for the oxygen reduction reaction

Electronic regulation of carbon is essential for developing non-platinum electrocatalysts for oxygen reduction reactions(ORRs).In this work,we used Cs to further regulate the electronic structure of nitrogen-doped(N-doped)carbon.The Cs atoms coordinated with the nitrogen atom in the N-doped carbon for injecting electrons into the carbon conjugate structure and reducing the work function of the carbon network.The low-work-function surface improved electron donation,facilitated O_(2) dissociation,and enhanced the adsorption of an OOH^(*) intermediate.Thus,electrocatalytic performance for the ORR was improved.The material shows potential as an ORR electrocatalyst comparable with Pt/C.

Tailoring electron transfer with Ce integration in ultrathin Co(OH)_(2) nanosheets by fast microwave for oxygen evolution reaction

The intrinsic activity of Co(OH)_(2) for oxygen evolution reaction(OER)may be elaborately improved through the suitable valence adjustment.Ce modification at electronic level is proved to be an efficient strategy owing to the flexible transformation of Ce^(3+)/Ce4+.Herein,Ce0.21@Co(OH)_(2) with the optimized Ce doping have been fabricated to tailor the fast electron transfer for the enhanced activity and stability for OER.Firstly,the obtained core-shell structure composed of vertical loose Co(OH)_(2) sheets not only exposes a large number of active sites,but also provides channels for Ce doping.Secondly,the high pressure microwave with instantaneous heating can fast introduce Ce into Co(OH)_(2),obtaining Cex@Co(OH)_(2) with well dispersion and close integration.The intimated interaction between Ce and Co species may provide the"d-f electronic ladders"for accelerating electron transfer of the catalytic surface.Meanwhile,Ce promotes the formation of Co-superoxide intermediate and/or the release of oxygen,which is considered to be the rate-determining step for OER.The electrochemical measurements confirmed the low overpotential of 300 m V at 10 m A cm^(-2) and great stability of Ce0.21@Co(OH)_(2) for OER.This work demonstrates a meaningful approach to realize the tuned electronic structure through metal doping.

Synchronous regulation of morphology and electronic structure of FeNi-P nanosheet arrays by Zn implantation for robust overall water splitting

FeNi-based phosphides are one of the most hopeful electrocatalysts,whereas the significant challenge is to achieve prominent bifunctional catalytic activity with low voltage for water splitting.The morphology and electronic structure of FeNi-based phosphides can intensively dominate effective catalysis,therefore their simultaneous regulating is extremely meaningful.Herein,a robust bifunctional catalyst of Zn-implanted FeNi-P nanosheet arrays(Zn-FeNi-P)vertically well-aligned on Ni foam is successfully fabricated by Zn implanting strategy.The Zn fulfills the role of electronic donor due to its low electronegativity to enhance the electronic density of FeNi-P for optimized water dissociation kinetics.Meanwhile,the implantation of Zn into FeNi-P can effectively regulate morphology of the catalyst from thick and irregular nanosheets to ultrathin lamellar structure,which generates enriched catalytic active sites,leading to accelerating electron/mass transport ability.Accordingly,the designed Zn-FeNi-P catalyst manifests remarkable hydrogen evolution reaction(HER)activity with low overpotentials of 55 and 225 mV at 10 and 200 mA·cm^(−2),which is superior to the FeNi-P(82 mV@10 mA·cm^(−2)and 301 mV@200 mA·cm^(−2)),and even out-performing the Pt/C catalyst at a high current density>200 mA·cm^(−2).Moreover,the oxygen evolution reaction(OER)activity of Zn-FeNi-P also has dramatically improved(207 mV@10 mA·cm^(−2))comparable to FeNi-P(221 mV@10 mA·cm^(−2))and RuO_(2)(239 mV@10 mA·cm^(−2)).Noticeably,an electrolyzer based on Zn-FeNi-P electrodes requires a low cell voltage of 1.47 V to achieve 10 mA·cm^(−2),far beyond the catalytic activities of FeNi-P||FeNi-P(1.51 V@10 mA·cm^(−2))and the benchmark RuO_(2)||Pt/C couples(1.56 V@10 mA·cm^(−2)).This Zn-implanting strategy paves a new perspective for the development of admirable bifunctional catalysts.

Single-atom sites regulation by the second-shell doping for efficient electrochemical CO_(2)reduction

Nitrogen-doped carbon loaded single-atom catalysts(SACs)are promising candidates for electrocatalytic conversion of CO_(2)into high-valuable chemicals,and the modification of catalysts by heteroatom-doping strategy is an effective approach to enhance the CO_(2)reduction performance.However,the large difference exists in atomic radius between nitrogen atoms and the doped heteroatoms may lead to the poor stability of active sites.In this study,we have synthesized a Ni single atom catalyst with S doping at the secondshell on the ultrathin carbon nanosheets support(Ni-N_(4)-SC)by solid-phase pyrolysis.The S atom in the second-shell contributes to the higher efficiency of CO_(2)conversion at lower potentials while the Ni-N_(4)-SC can be more stable.The experimental results and theoretical calculations indicate that the S atom in second-shell breaks the uniform charge distribution and reduces the free energy of hydrogenation,which can increase the adsorption of CO_(2),accelerate charge transfer,and reduce the reaction energy barrier.This work reveals the close relationship between the second-shell and the electrocatalytic activity of single atom sites,which also provides a new perspective to design efficient single atom catalysts.

High-performance Bi_(2)S_(3)/ZnO photoanode enabled by interfacial engineering with oxyanion for efficient photoelectrochemical water oxidation

In the present contribution,we demonstrate that the sluggish kinetics of oxygen evolution reaction(OER)over the bismuth sulfide(Bi_(2)S_(3))photoanode,which severely restricts its photoelectrochemical activity,is markedly accelerated by employing a sulfatecontaining electrolyte.First-principle calculation points to the spontaneous adsorption of sulfate(SO_(4)^(2−))on Bi_(2)S_(3)and its capacity of stabilizing the OER intermediates through hydrogen bonding,which is further reinforced by increasing the local density of states near the Fermi level of Bi_(2)S_(3).Meanwhile,the electron transfer is also promoted to synergistically render the ratedetermining step(from O*to OOH*)of OER over Bi_(2)S_(3)kinetically facile.Last but not least,benefitting from such enhanced OER activity and efficient charge separation resulted from depositing Bi_(2)S_(3)on the zinc oxide nanorods(ZnO NRs),forming a core–shell heterojunction,its photocurrent density achieves 8.61 mA·cm^(−2)at 1.23 VRHE,far surpassing those reported for additional Bi_(2)S_(3)-based and several state-of-the-art photoanodes in the literature and further exceeding their theoretical limit.The great promise of the Bi_(2)S_(3)/ZnO NRs is in view of such outperformance,the superior Faradaic yield of oxygen of more than~80%and the outstanding half-cell applied bias photon-to-current efficiency of~1%well corroborated.

不对称配位操纵电子再分布实现高电流密度下电催化水氧化

作为目前最有前景的绿氢生产方式,电解水技术被研究者广泛关注.其中,电催化析氧反应(oxygen evolution reaction,OER)作为电解水的半反应,由于其缓慢的四电子转移步骤而成为电解水器件的能量瓶颈.高效的OER催化电极设计是解决该问题的有效方式.本文分析了OER催化剂中氧原子介导的电子重排与活性位点配位不对称性之间的构效关系.通过自发氧化还原反应,将镍离子引入到泡沫镍(NF)表面的FeWO_(4)中,以此破坏FeWO_(4)晶格中FeO_(6)八面体的对称性,并基于此调节Fe位点的电子结构.结构调控促进了钨酸盐适度重构成为具有高OER活性的羟基氧化物.在碱性环境中,具有不对称配位Fe位点的Fe_(0.53)Ni_(0.47)WO_(4)/NF自支撑电极在10 mA cm^(-2)的电流密度下,可获得170 mV的超低过电势,并在1000 mA cm^(-2)的高电流密度下可维持稳定500 h.这种新型OER催化电极为高活性电催化系统的设计提供了新的见解.

Mott-Schottky异质结对金属电子态持续调控促进乙醇氧化C-C断裂

直接乙醇燃料电池的效率与阳极乙醇氧化反应(EOR)C1路径选择性密切相关,然而C-C键断裂的能垒较高,使得C1路径产物选择性低,从而限制了直接乙醇燃料电池效率的提升.设计具有高C-C裂解效率的电催化剂,对于构建高效直接乙醇燃料电池具有重要意义.本文报道了一种Mott-Schottky异质结调节催化活性中心电子状态从而促进EOR过程中C-C裂解的新策略.我们以PdAu合金纳米颗粒(NPs)为模型催化剂,制备了PdAu@N_(x)C金属-碳Mott-Schottky异质结构.PdAu NPs(15.9±1.9 nm)均匀地分散在N掺杂的碳载体上.我们通过在宽范围内调节N掺杂量,调控异质结界面电势,形成了不同程度的电荷分离.通过催化剂结构与性能研究,建立了反应活性与催化剂功函数之间的线性关系,表明金属/碳界面电子转移可以有效促进EOR.优化的催化剂PdAu@N10.69C,显示出高C1产物选择性(FE=51.1%),质量活性(MA=9.7 A mg Pd^(-1))和比活性(SA=13.2 mA cm^(-2)),优于PdAu@C和大多数报道的Pd基EOR催化剂.实验结果和理论计算表明,N的引入促进了电子由碳层向PdAu转移,加强了对*CH_(3)CO的吸附,从而提高了C-C键的断裂效率.这项工作为整流策略提高EOR性能提供了一种新的研究思路.

Reduced water dissociation barrier on constructing Pt-Co/CoO_(x)interface for alkaline hydrogen evolution

Water dissociation process is generally regarded as the rate-limiting step for alkaline hydrogen evolution reaction(HER),and severely inhibits the catalytic efficiency of Pt based catalysts.To overcome this problem,the in-situ constructed interfaces of PtCo alloy and amorphous cobalt oxide(CoO_(x))on the carbon powder are designed.The amorphous CoO_(x)at Pt-Co/CoO_(x)interfaces not only provide active sites for water dissociation to facilitate Volmer step,but also produce the strong electronic transfer with Pt-Co.Accordingly,the obtained interfacial catalysts exhibit outstanding alkaline HER performance with a Tafel slope of 29.3 mV·dec^(−1)and an ultralow overpotential of only 28 mV at 10 mA·cm^(−2).Density functional theory(DFT)reveals that the electronic accumulation on the interfacial Co atom in Pt-Co/CoO_(x)constructing the novel active site for water dissociation.Compared to the Pt-Co,all of the energy barriers for water adsorption,water dissociation and hydrogen adsorption/desorption are reduced in Pt-Co/CoO_(x)interfaces,suggesting a boosted HER kinetics for alkaline HER.