Solid Bi_(2)O_(3)-derived nanostructured metallic bismuth with high formate selectivity for the electrocatalytic reduction of CO_(2)

CO_(2) electrochemical reduction(CO_(2)ER)is an important research area for carbon neutralization.However,available catalysts for CO_(2) reduction are still characterized by limited stability and activity.Recently,metallic bismuth(Bi)has emerged as a promising catalyst for CO_(2) ER.Herein,we report the solid cathode electroreduction of commercial micronized Bi2O3as a straightforward approach for the preparation of nanostructured Bi.At-1.1 V versus reversible hydrogen electrode in a KHCO3aqueous electrolyte,the resulting nanostructure Bi delivers a formate current density of~40 mA·cm^(-2) with a current efficiency of~86%,and the formate selectivity reaches97.6% at-0.78 V.Using nanosized Bi2O3as the precursor can further reduce the primary particle sizes of the resulting Bi,leading to a significantly increased formate selectivity at relatively low overpotentials.The high catalytic activity of nanostructured Bi is attributable to the ultrafine and interconnected Bi nanoparticles in the nanoporous structure,which exposes abundant active sites for CO_(2) electrocatalytic reduction.

Bimetallic In_(2)O_(3)/Bi_(2)O_(3) Catalysts Enable Highly Selective CO_(2) Electroreduction to Formate within Ultra-Broad Potential Windows

CO_(2)electrochemical reduction reaction(CO_(2)RR)to formate is a hopeful pathway for reducing CO_(2)and producing high-value chemicals,which needs highly selective catalysts with ultra-broad potential windows to meet the industrial demands.Herein,the nanorod-like bimetallic ln_(2)O_(3)/Bi_(2)O_(3)catalysts were successfully synthesized by pyrolysis of bimetallic InBi-MOF precursors.The abundant oxygen vacancies generated from the lattice mismatch of Bi_(2)O_(3)and ln_(2)O_(3)reduced the activation energy of CO_(2)to*CO_(2)·^(-)and improved the selectivity of*CO_(2)·^(-)to formate simultaneously.Meanwhile,the carbon skeleton derived from the pyrolysis of organic framework of InBi-MOF provided a conductive network to accelerate the electrons transmission.The catalyst exhibited an ultra-broad applied potential window of 1200 mV(from-0.4 to-1.6 V vs RHE),relativistic high Faradaic efficiency of formate(99.92%)and satisfactory stability after 30 h.The in situ FT-IR experiment and DFT calculation verified that the abundant oxygen vacancies on the surface of catalysts can easily absorb CO_(2)molecules,and oxygen vacancy path is dominant pathway.This work provides a convenient method to construct high-performance bimetallic catalysts for the industrial application of CO_(2)RR.

1.42-fold enhancement of formate selectivity by linker conversion on the Zn-based metal organic framework catalyst

Electro-reduction of carbon dioxide(ERCO_(2)) is considered an effective method to alleviate the greenhouse effect and produce value-added chemicals.Achieving the dominant selectivity of Zn-based catalysts for formate remains a challenge.In this article,the ZnIn-E_(12) catalyst is successfully prepared by solvent assisted ligand exchange(SALE) method to convert organic ligands,achieving a Faradaic efficiency of 72.28% for formate at-1.26 V vs.RHE(V_(RHE)),which is 1.42 times higher than the original catalyst.Evidence shows that the successful conversion of organic ligands can transform the catalyst from the original large size polyhedron to cross-linked network of particles with a diameter of about 30 nm.The increased specific surface area can expose more active sites and facilitate the electrocatalytic conversion of CO_(2) to formate.This work is expected to provide inspiration for the regulation of formate selectivity and catalyst size in Zn-based catalysts.

Plasma-assisted synthesis of porous bismuth nanosheets for electrocatalytic CO_(2)-to-formate reduction

The electrochemical carbon dioxide reduction(eCO_(2)RR)to formate,driven by clean energy,is a promising approach for producing renewable chemicals and high-value fuels.Despite its potential,further development faces challenges due to limitations in electrocatalytic activity and durability,especially for nonnoble metal-based catalysts.Here,naturally abundant bismuth-based nanosheets that can effectively drive CO_(2)-to-formate electrocatalytic reduction are prepared using the plasma-activated Bi_(2)Se_(3) followed by a reduction process.Thus-obtained plasma-activated Bi nanosheets(P-BiNS)feature ultrathin structures and high surface areas.Such nanostructures ensure the P-BiNS with outstanding eCO_(2)RR catalytic performance,highlighted by the current density of over 80 mA cm^(-2) and a formate Faradic efficiency of>90%.Furthermore,P-BiNS catalysts demonstrate excellent durability and stability without deactivation following over 50h of operation.The selectivity for formate production is also studied by density functional theory(DFT)calculations,validating the importance and efficacy of the stabilization of intermediates(^(*)OCHO)on the P-BiNS surfaces.This study provides a facile plasma-assisted approach for developing high-performance and low-cost electrocatalysts.

Porous Indium Nanocrystals on Conductive Carbon Nanotube Networks for High-Performance CO_(2)-to-Formate Electrocatalytic Conversion

Ever-increasing emissions of anthropogenic carbon dioxide(CO_(2))cause global environmental and climate challenges.Inspired by biological photosynthesis,developing effective strategies NeuNlto up-cycle CO_(2)into high-value organics is crucial.Electrochemical CO_(2)reduction reaction(CO_(2)RR)is highly promising to convert CO_(2)into economically viable carbon-based chemicals or fuels under mild process conditions.Herein,mesoporous indium supported on multi-walled carbon nanotubes(mp-In@MWCNTs)is synthesized via a facile wet chemical method.The mp-In@MWCNTs electrocatalysts exhibit high CO_(2)RR performance in reducing CO_(2)into formate.An outstanding activity(current density-78.5 mA cm^(-2)),high conversion efficiency(Faradaic efficiency of formate over 90%),and persistent stability(∼30 h)for selective CO_(2)-to-formate conversion are observed.The outstanding CO_(2)RR process performance is attributed to the unique structures with mesoporous surfaces and a conductive network,which promote the adsorption and desorption of reactants and intermediates while improving electron transfer.These findings provide guiding principles for synthesizing conductive metal-based electrocatalysts for high-performance CO_(2)conversion.

A Revisit to the Role of Bridge-adsorbed Formate in the Electrocatalytic Oxidation of Formic Acid at Pt Electrodes

The mechanism and kinetics of electrocatalytic oxidation of formic acid at Pt electrodes is discussed in detail based on previous electrochemical in-situ ATR-FTIRS data [Langmuir 22, 10399 （2006）and Angewa. Chem. Int. Ed. 50, 1159 （2011）]. A kinetic model with formic acid adsorption （and probably the simultaneous C-H bond activation） as the rate determining step, which contributes to the majority of reaction current for formic acid oxi- dation, was proposed for the direct pathway. The model simulates well the IR spectroscopic results obtained under conditions where the poisoning effect of carbon monoxide （CO） is negligible and formic acid concentration is below 0.1 mol/L. The kinetic simulation predicts that in the direct pathway formic acid oxidation probably only needs one Pt atom as active site, formate is the site blocking species instead of being the active intermediate. We review in detail the conclusion that formate pathway （with either 1st or 2nd order reaction kinetics） is the direct pathway, possible origins for the discrepancies are pointed out.

Determination of Isotherm for Acetate and Formate Adsorption at Pt（111） Electrode by Fast Scan Voltammetry

Fast scan voltammetry is an efficient tool to distinguish oxidative/reductive adsorp- tion/desorption from that for bulk reaction. In this work, we provide a methodology that the isotherm of oxidative/reductive adsorption desorption processes at electrode surface can be obtained using just one solution with relatively low reactant concentration, by taking the advantage of varying the potential scan rate （relative of the diffusion rate） to tune the adsorption rate and proper mathematic treatment. The methodology is demonstrated by taking acetate adsorption at Pt（lll） in acidic solution as an example. The possibility for extension of this method toward mechanistic studies of complicated electrocatalytic reactions is also given.

Role of Bridge-bonded Formate in Formic Acid Dehydration to CO at Pt Electrode： Electrochemial in-situ Infrared Spectroscopic Study

Formic acid （HCOOH） decomposition at Pt film electrode has been studied by electrochem- ical in situ FTIR spectroscopy under attenuated-total-reflection configuration, in order to clarify whether bridge-bonded formate （HCOOD） is the reactive intermediate for COad for-mation from HCOOH molecules. When switching from HCOOH-free solution to HCOOH- containing solution at constant potential （E=0.4 V vs. RHE）, we found that immediately upon solution switch COad formation rate is the highest, while surface coverage of formate is zero, then after COad formation rate decreases, while formate coverage reaches a steady state coverage quickly within ca. 1 s. Potential step experiment from E=0.75 V to 0.35 V, reveals that formate band intensity drops immediately right after the potential step, while the COad signal develops slowly with time. Both facts indicate that formate is not the reactive intermediate for formic acid dehydration to CO.

Challenges and opportunities for using formate to store, transport, and use hydrogen

In this perspective article,the synthesis and thermodynamic properties of aqueous solutions of formate salts(FS,HCO2-)are described in relationship to the concept of H2carriers.The physiochemical properties of solid FS,aqueous formate solutions,and aqueous bicarbonate solutions set the limitations for storage capacity,deliverable capacity,and usable H2capacity of these H2carriers,respectively.These parameters will help in the design of systems that use H2carriers for storage and transport of H2for fuel cell power applications.FS,as well as admixtures with formic acid(FA,H2CO2),have potential to address the goals outlined in the U.S.Department of Energy’s H2@scale initiative to store in chemical bonds a significant quantity of energy(hundreds of megawatts)obtained from large scale renewable resources.

Nitrogen doped tin oxide nanostructured catalysts for selective electrochemical reduction of carbon dioxide to formate

Tin/tin oxide materials are key electrocatalysts for selective conversion of CO;to formate/formic acid.Herein we report a tin oxide material with nitrogen doping by using ammonia treatment at elevated temperature. The N doped material demonstrated enhanced electrocatalytic CO;reduction activity, showing high Faradaic efficiency（90%） for formate at -0.65 V vs. RHE with partial current density of 4 mA/cm;.The catalysis was contributed to increased electron negativity of N atom compared to O atom. Additionally, the N-doped catalyst demonstrates sulfur tolerance with retained formate selectivity. The analysis after electrolysis shows that the catalyst structure partially converts to metallic Sn, and thus the combined Sn/N-SnO;is the key for the active CO;catalysis.

Die sinter bonding in air using copper formate preform for formation of full-density bondline

Pressure-assisted sinter bonding was performed in air at 250−350℃ using a preform comprising copper formate particles to form a bondline that is sustainable at high temperatures.H2 and CO generated concurrently by the pyrolysis of copper formate at 210℃ during the sinter bonding removed the native oxide and other oxides grown on bulk Cu finishes,enabling interface bonding.Moreover,Cu produced in situ by the reduction of Cu(II)accelerated the sinter bonding.Consequently,the bonding achieved at 300−350℃ under 5 MPa exhibited sufficient shear strength of 20.0−31.5 MPa after 180−300 min of sinter bonding.In addition,an increase in pressure to 10 MPa resulted in shear strength of 21.9 MPa after an extremely short time of 30 s at 250℃,and a near-full-density bondline was achieved after 300 s.The obtained results indicate the promising potential of the preform comprising copper formate particles for high-speed sinter bonding.

Ni nanoparticles confined by yolk-shell structure of CNT-mesoporous carbon for electrocatalytic conversion of CO_(2): Switching CO to formate

Electrochemical reduction of CO_(2)(CO_(2)ER) to formate has been a promising route to produce value-added chemicals.Developing low-cost and efficient electrocatalysts with high product selectivity is still a grand challenge.Herein,a novel Ni nanoparticles-anchored CNT coated by mesoporous carbon with yolk-shell structure (CNT/Ni@mC) catalysis was designed for CO_(2)ER.Ni nanoparticles were confined in the cavity between CNT and mesoporous carbon shell and the confined space can be controlled by tuning the amount of silica precursor.The mesoporous carbon shell and confined space are beneficial to charge transmission during CO_(2)ER.In contrast to previous studies,the CNT/Ni@mC catalyst presents selectivity toward formate rather than CO.Electrochemical in situ attenuated total reflection Fourier transform infrared spectroscopy measurements indicate the presence of a COO* intermediate that converts to formate under CO_(2)ER conditions.The well-defined structural feature of the confined space of the Ni-based catalyst for selective CO_(2)ER to formate may facilitate in-depth mechanistic understandings on structural factors that affect CO_(2)ER performance.

Surface Oxygen Injection in Tin Disulfide Nanosheets for Efficient CO_(2) Electroreduction to Formate and Syngas

Surface chemistry modification represents a promising strategy to tailor the adsorption and activation of reaction intermediates for enhancing activity.Herein,we designed a surface oxygen-injection strategy to tune the electronic structure of SnS_(2) nanosheets,which showed effectively enhanced electrocatalytic activity and selectivity of CO_(2) reduction to formate and syngas(CO and H_(2)).The oxygen-injection SnS_(2) nanosheets exhibit a remarkable Faradaic efficiency of 91.6%for carbonaceous products with a current density of 24.1 mA cm^(−2) at−0.9 V vs RHE,including 83.2%for formate production and 16.5%for syngas with the CO/H_(2) ratio of 1:1.By operando X-ray absorption spectroscopy,we unravel the in situ surface oxygen doping into the matrix during reaction,thereby optimizing the Sn local electronic states.Operando synchrotron radiation infrared spectroscopy along with theoretical calculations further reveals that the surface oxygen doping facilitated the CO_(2) activation and enhanced the affinity for HCOO*species.This result demonstrates the potential strategy of surface oxygen injection for the rational design of advanced catalysts for CO_(2) electroreduction.

Regulating surface In–O in In@InO_(x) core‐shell nanoparticles for boosting electrocatalytic CO_(2) reduction to formate

To solve the excessive emission of CO_(2) caused by the excessive use of fossil fuels and the corre‐sponding environmental problems,such as the greenhouse effect and climate warming,electrocat‐alytic CO_(2) reduction to liquid fuel with high selectivity is of huge significance for energy conversion and storge.Indium has been considered as a promising and attractive metal for the reduction of CO_(2) to formate.However,the current issues,such as low selectivity and current activity,largely limit the industrial application for electrocatalytic CO_(2) reduction,the design optimization of the catalyst structure and composition is extremely important.Herein,we develop a facile strategy to regulate surface In–O of In@InO_(x) core‐shell nanoparticles and explore the structure‐performance relation‐ship for efficient CO_(2)‐to‐formate conversion though air calcination and subsequent in situ electro‐chemical reconstruction,discovering that the surface In–O is beneficial to stabilize the CO_(2) interme‐diate and generate formate.The optimized AC‐In@InO_(x)‐CNT catalyst exhibits a C1 selectivity up to 98%and a formate selectivity of 94%as well as a high partial formate current density of 32.6 mA cm^(-2).Furthermore,the catalyst presents an excellent stability for over 25 h with a limited activity decay,outperforming the previously reported In‐based catalysts.These insights may open up op‐portunities for exploiting new efficient catalysts by manipulating their surface.

Novel Synthetic Method for the Vilsmeier-Haack Reagent and Green Routes to Acid Chlorides, Alkyl Formates, and Alkyl Chlorides

An environmentally benign and practical preparation method for the Vilsmeier-Haack reagent (VH) has been developed by using phthaloyl dichloride with DMF in toluene or 2-chlorotoluene. Phthalic anhydride as the byproduct was recovered in high yield by simple filtration. Some aromatic acids have been transformed into the corresponding acid chlorides in good yields by employing the isolated VH. Treatment of primary or secondary alcohols with VH gave alkyl formates or alkyl chlorides by depending on the reaction conditions.

Promoting effect of chloride ions on selective oxidation of methanol to methyl formate over zirconia-supported ruthenium oxide catalysts

The effect of chloride ions on a monoclinic ZrO2-supported RuOx （RuOx/m-ZrO2） catalyst with a Ru surface density of 0.3 Ru/nm2 was studied in the selective oxidation of methanol to methyl formate （MF） at a low temperature of 373 K. The m-ZrO2 support was Cl-free, and Cl- ions were introduced into the RuOx/m-ZrO2 catalyst by impregnation with zirconium oxychloride or ammonium chloride and subsequent thermal treatment in air at 673 K. The structures of these catalysts were characterized by X-ray diffraction, Raman and X-ray photoelectron spectroscopies. Their reducibility was probed by temperature-programmed reduction in H2. The RuOx domains were present as highly dispersed Rut42- structure on m-ZrO2 with similar reducibility for the RuOx/m-ZrO2 samples irrespective of modification with or without Cl ions. Introduction of appropriate amounts of zirconium oxychloride into RuOx/m-ZrO2 led to a remarkable increase in the methanol oxidation rate and MF selectivity, whereas introduction of ammonium chloride or zirconyl nitrate significantly inhibited the catalytic performance of RuOx/m-ZrO2. The promoting effect of Cl- ions derived from zirconium oxychloride can be tentatively attributed to their roles in facilitating the adsorption of methanol and desorption of MF product or its intermediates. This finding provides novel insights into the promoting effect of Cl- ions on oxides-based catalysts for selective oxidation reactions.

Efficient CO_(2)Reduction to Formate on CsPbI_(3) Nanocrystals Wrapped with Reduced Graphene Oxide

Transformation of greenhouse gas(CO_(2))into valuable chemicals and fuels is a promising route to address the global issues of climate change and the energy crisis.Metal halide perovskite catalysts have shown their potential in promoting CO_(2)reduction reaction(CO_(2)RR),however,their low phase stability has limited their application perspective.Herein,we present a reduced graphene oxide(rGO)wrapped CsPbI_3 perovskite nanocrystal(NC)CO_(2)RR catalyst(CsPbI_3/rGO),demonstrating enhanced stability in the aqueous electrolyte.The CsPbI_3/rGO catalyst exhibited>92%Faradaic efficiency toward formate production at a CO_(2)RR current density of~12.7 mA cm^(-2).Comprehensive characterizations revealed the superior performance of the CsPbI_3/rGO catalyst originated from the synergistic effects between the CsPbI_3 NCs and rGO,i.e.,rGO stabilized theα-CsPbI_3 phase and tuned the charge distribution,thus lowered the energy barrier for the protonation process and the formation of~*HCOO intermediate,which resulted in high CO_(2)RR selectivity toward formate.This work shows a promising strategy to rationally design robust metal halide perovskites for achieving efficient CO_(2)RR toward valuable fuels.

In-situ constructing Cu_(1)Bi_(1)bimetallic catalyst to promote the electroreduction of CO_(2)to formate by synergistic electronic and geometric effects

Electrochemical CO_(2)reduction to formate is a potential approach to achieving global carbon neutrality.Here,Cu1Bi1bimetallic catalyst was prepared by a co-precipitation method.It has a ginger like composite structure(CuO/CuBi_(2)O_(4))and exhibited a high formate faradaic efficiency of 98.07%at–0.98 V and a large current density of–56.12 mA.cm^(-2)at–1.28 V,which is twice as high as Bi2O3catalyst.Especially,high selectivity(FE^(–)_(HCOO)>85%)is maintained over a wide potential window of 500 mV.In-situ Raman measurements and structure characterization revealed that the reduced Cu1Bi1bimetallic catalyst possesses abundant Cu-Bi interfaces and residual Bi-O structures.The abundant Cu-Bi interface structures on the catalyst surface can provide abundant active sites for CO_(2)RR,while the Bi-O structures may stabilize the CO_(2)^(*–)intermediate.The synergistic effect of abundant Cu-Bi interfaces and Bi-O species promotes the efficient synthesis of formate by following the OCHO^(*)pathway.

Pd nanoparticles immobilized on MIL-53(Al)as highly e ective bifunctional catalysts for oxidation of liquid methanol to methyl formate

A series of Pd/MIL-53(Al) heterogeneous bifunctional catalysts with di erent Pd contents were prepared by an impregnation method. The prepared metal–organic frameworks MIL-53(Al) and catalysts were characterized by XRD, SEM, HRTEM,FT-IR and N2 adsorption/desorption techniques. The results showed that MIL-53(Al) was synthesized successfully, and the structure was unchanged during and after the preparation of the catalysts. The Pd nanoparticles(NPs) with an average particle size of 4.6 nm were uniformly dispersed on the MIL-53(Al). The catalyst exhibited good catalytic activity in the selective oxidation of liquid methanol to methyl formate. Under the conditions of 150 °C, 2 MPa O2 and solvent-free for5 h, the conversion of methanol could reach 60.3%, and the selectivity of methyl formate was up to 62.2%. In addition, the Pd/MIL-53(Al) bifunctional catalyst exhibited excellent stability and maintained high catalytic activity after five cycles.

Metal oxides heterojunction derived Bi-In hybrid electrocatalyst for robust electroreduction of CO_(2) to formate

Electrochemical reduction of Bi-based metal oxides is regarded as an effective strategy to rationally design advanced electrocatalysts for electrochemical CO_(2)reduction reaction(CO_(2)RR).Realizing high selectivity at high current density is important for formate production,but remains challenging.Herein,the BiIn hybrid electrocatalyst,deriving from the Bi2O3/In2O3heterojunction(MOD-Biln),shows excellent catalytic performance for CO_(2)RR.The Faradaic efficiency of formate(FEHCOO-) can be realized over 90% at a wide potential window from-0.4 to-1.4 V vs.RHE,while the partial current density of formate(jHCOO-) reaches about 136.7 mA cm^(-2)at-1.4 V in flow cell without IR-compensation.In additio n,the MOD-Biln exhibits superior stability with high selectivity of formate at 100 mA cm^(-2).Systematic characterizations prove the optimized catalytic sites and interface charge transfer of MOD-Biln,while theoretical calculation confirms that the hybrid structure with dual Bi/In metal sites contribute to the optimal free energy of*H and*OCHO intermediates on MOD-Biln surface,thus accelerating the formation and desorption step of*HCOOH to final formate production.Our work provides a facile and useful strategy to develop highly-active and stable electrocatalysts for CO_(2)RR.