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Herein, a hierarchically ordered porous superstructure of N-doped carbon embedded with readily accessible Fe-Ni diatomic sites (FeNi DASs/HOPSNC) has been synthesized for highly efficient CO 2 electroreduction. By integrating additional secondary mesopores into the ordered macroporous skeleton, this distinctive superstructure exhibits greatly enhanced accessibility and mass transfer. Benefiting from the unique structure merits including the synergistic effect in Fe-Ni atomic pair sites and the multi-level porosity, such diatomic site catalyst affords an outstanding electrocatalytic performance with excellent activity and selectivity for CO 2 -to-CO conversion and remarkable stability. Furthermore, systematic characterizations and density functional theory calculations unveiled that the electronic interaction within the diatomic pairs leads to the optimized electronic state and decreased reaction energy barrier for generating COOH* intermediate and weakening the binding strength of CO*, thereby improving the intrinsic catalytic activity and selectivity. This work may inspire further development of high-performance diatomic site catalysts for CO 2 electroreduction and other electrosynthesis. [Display omitted] • A hierarchically ordered porous superstructure with readily accessible atomic pair sites is constructed. • The ordering and uniformity of multiscale pores in MOF-derived carbon materials is controlled. • The Fe-Ni diatomic catalyst (DAC) shows synergistic electronic interaction between the two adjacent metal atoms. • A high Faradaic efficiency of 94.5%, large current densities up to 300 mA cm−2 and remarkable durability are obtained. [ABSTRACT FROM AUTHOR]

Au x Cu 1-x thin films were synthesized by pulsed laser deposition (PLD) and their electrocatalytic properties towards CO 2 reduction in aqueous solution were assessed. The presence of an O 2 atmosphere during the PLD process modified the chemical nature of the resulting Au x Cu 1-x films, with different oxide types identified by X-ray photoelectron spectroscopy. The impact of these oxides, and of the Cu/Au stoichiometry, on the partial current density and conversion efficiency were assessed. The formation of Au x Cu 1-x alloy thin films and/or the introduction of an O 2 atmosphere during deposition does not yield to any marked increase of the formation of carbonaceous compounds, and CO and H 2 were the only two products formed, along with formate detected in trace amounts ( < 1%). Oxide-derived Au catalysts obtained by PLD under O 2 atmosphere do not alter CO 2 selectivity towards CO formation. High copper content catalysts deposited in vacuum exhibit the lowest overall CO FE%, while increasing the Au content enhances it. The same trend is observed for Au x Cu 1-x catalysts deposited under 2 and 220 mTorr O 2 , aside from the fact that increasing Cu content under high O 2 pressure has a less negative influence on CO FE%. [ABSTRACT FROM AUTHOR]

Isolated metal-nitrogen sites are highly active to catalyze the oxygen and carbon dioxide electroreduction, however, the limited content of isolated metal-nitrogen sites within carbon matrix urgently requires full exposure of the active sites on the surface for efficient catalysis. Herein, post-synthetic modification strategy is explored to selectively confine ammonium ferric citrate on the surface of zeolitic imidazolate framework-8 (ZIF-8) nanoparticles. After pyrolysis, isolated iron-nitrogen sites are generated and located on the carbon matrix surface. The highly exposed iron-nitrogen sites demonstrate excellent mass activity toward oxygen reduction reaction in acidic medium, outperforming most reported non-noble metal catalysts, and also show superior selectivity and mass activity toward carbon dioxide electroreduction compared to most reported noble metal catalysts. [ABSTRACT FROM AUTHOR]

Pd/C catalysts facilitate CO 2 electroreduction to formate with high Faradaic efficiency at low overpotentials. However, they are prone to deactivation due to CO poisoning. In this work, three carbon-supported Pd-Pt catalysts with different metal deposition sequences are prepared and their efficacy towards formate production over the Pd surface is studied. X-ray photoelectron spectroscopy and X-ray absorption spectroscopy results show that the surface composition and coordination number of Pd-Pd in carbon-supported Pd-Pt catalysts are greatly influenced by the order in which Pd and Pt nanoparticles (NPs) are deposited. The deposition of Pt NPs prior to Pd NPs on the carbon support gives the best results for formate production with high Faradaic efficiency. [ABSTRACT FROM AUTHOR]

• M 3 (2,3,6,7,10,11-hexahydroxytriphenylene) 2 (M 3 (HHTP) 2) electrocatalytic CO 2 reduction was screened by theoretical calculations for better Cu 3 (HHTP) 2 production of methane. • The screened Cu 3 (HHTP) 2 catalysts were experimentally validated and found to have a relatively high faraday efficiency for methane. • The theoretical calculations agree with the experimental results. Metal-organic frameworks (MOFs) has shown promising applications in electrocatalytic CO 2 reductions due to their high specific surface area, abundant active sites and clear structure, but the conductivity of MOFs is a great challenge. Herein, a two-dimensional (2D) coordination network materials M 3 (2,3,6,7,10,11-hexahydroxytriphenylene) 2 (M 3 (HHTP) 2) with a good conductivity were systematically investigated and theoretical screened as promising electrocatalysts for the electrocatalytic carbon dioxide reduction reactions (CO 2 RR) combining density function theory (DFT) calculations and experimental validation. The theoretical calculations show that CH 4 is the main reduction product for CO 2 RR catalyzed by Cu 3 (HHTP) 2 and Ti 3 (HHTP) 2. However, favorable product by Sc 3 (HHTP) 2 , Co 3 (HHTP) 2 , Ni 3 (HHTP) 2 and Zn 3 (HHTP) 2 is CO. For V 3 (HHTP) 2 and Mn 3 (HHTP) 2 , HCHO is dominant product, but the reaction of V 3 (HHTP) 2 catalyst required a high overpotential above 1.69 V. HCOOH is primarily produced from Cr 3 (HHTP) 2 and Fe 3 (HHTP) 2. Furthermore, the electrochemical CO 2 RR catalyzed by Cu 3 (HHTP) 2 and Ni 3 (HHTP) 2 were completed to validate theoretical screening. It is found that Cu 3 (HHTP) 2 hold excellent CO 2 RR activity with 42.88% Faraday efficiency (FE) of CH 4 with 107.92 mA cm−2 at -1.30 V vs RHE, and Ni 3 (HHTP) 2 has 68.27% CO FE with a current density of 59.92 mA cm−2 at -0.50 V vs RHE. This work showed that theoretical screening work can provide a highly effective approach to investigate the reaction mechanism and can aid in designing novel catalysts for CO 2 RR, and would greatly promote design of MOF catalysts for CO 2 RR. [Display omitted] [ABSTRACT FROM AUTHOR]

The study of the electrocatalytic activity of the Fe(II)-meso-tetraphenylporphyrin tetrasulphonate ([Fe(II)TPPS4]o), towards the redox processes for CO, HCOOH, H2CO y CO2 is reported. The [Fe(II)TPPS4]o seems to form stable species with CO and HCOOH through a coupled chemical reaction, and this species hardly undergoes further oxidation to CO2. Contrary to this behavior, HCOOH and CO2 were readily obtained as oxidation products from H2CO. On the other hand, by means of a spectroelectrochemical study, it was found that CO2 is electrochemically reduced in two consecutive steps; the first step occurs at about -1200 mV, and is attributed to the loss of linearity of CO2 molecule, while the second step, at about 1400 mV, would involve its conversion to formate-like species. The products of CO2 electroreduction were determined by chromatography and include HCOOH, CO and traces of some short chain hydrocarbon species.

• Porous PANI with satisfactory CO 2 capture and spillover capability triggers CO 2 activity of TcPcCo in thermodynamics and kinetics. • PANI-TcPcCo/CP delivers over 95% FE CO at a potential range of 450 mV, ranking foremost among the reported phthalocyanine-based catalysts. • This work presents a new perspective on advancing the catalytic capability of molecular materials by regulating the local chemical environment. Metallophthalocyanines (MPcs) with the especially active metal-N 4 catalytic sites have the great potential for the electrocatalytic CO 2 -to-CO conversion. However, the masking of metal-N 4 catalytic sites attributed to the strong π-π interaction and the difficulty in capturing CO 2 severely limits their catalytic efficiency. Herein, we designed a self-supported electrode that tetra-β-carboxy phthalocyanine cobalt(II) (TcPcCo) was anchored into polyaniline (PANI) chain in isolation using the carbon paper (CP) as a support. The PANI with unique porous structure provides large surface area, rapid electron transfer, and unimpeded pathways for CO 2 diffusion. More importantly, sufficient CO 2 captured by PANI can continuously spill over to metal-N 4 active sites and be reduced into CO. The synthesized electrode for CO 2 reduction reaction (CO 2 RR) could maintain a high CO Faraday efficiency of over 95% (maximum 99.3%) at an extraordinary wide potential range of 450 mV (from -0.50 V to -0.95 V vs. RHE), ranking foremost among the previously reported phthalocyanine-based electrocatalysts. Furthermore, relative to TcPcCo, the CO turnover frequency (TOF) of PANI-TcPcCo/CP significantly improves, especially at the more negative operating potential (about 7 ∼ 68 times). Theoretical calculations further reveal that the introduce of PANI optimizes the free energy barrier of CO 2 RR intermediate at Co-N 4 site, thus accommodating the*COOH formation, and also suppresses the competition of hydrogen evolution reaction. This work presents a new perspective on advancing the catalytic CO 2 RR capability of molecular materials by regulating the chemical environment surrounding a catalytically active site. [Display omitted] [ABSTRACT FROM AUTHOR]

Pyridinic nitrogen of nitrogen-doped carbon materials (NCMs) has been recognized as the most active site for electrochemical reduction of CO 2 to CO. To pursue high content of pyridinic nitrogen, conventional nitrogen doping performed at high temperature in inert atmosphere requires consuming large amounts of nitrogenous precursor. Here, an efficient and cost-effective strategy was proposed to construct nitrogen-doped carbon nanotubes (NCNTs) with high concentration of pyridinic nitrogen (38.9 % of all nitrogen) by annealing the blend of low mass ratio of dicyandiamide (DCDA) and oxidized carbon nanotubes (CNTs-O) at 550 °C in H 2 /Ar atmosphere. The as-prepared NCNTs (N 0.5 CNTs-550-H 2) demonstrated an exceptional CO Faraday efficiency (FE CO) of 96.2 % and a satisfying CO current density (j CO) of −11.8 mA cm−2 at −0.9 V RHE , and exhibited high FE CO (> 90 %) in the wide electrochemical window of −0.8 to −1.2 V RHE. The high performance of N 0.5 CNTs-550-H 2 is attributed to the favorable annealing in a moderate-temperature H 2 atmosphere for the formation of pyridinic nitrogen, which acts as the most active site and favors the production of CO in CO 2 ER. [Display omitted] • A cost-effective route to construct NCNTs with rich pyridinic nitrogen is proposed. • An exceptional CO faraday efficiency of 96.2 % with the current density of −11.8 mA cm−2 was achieved. • A high CO faraday efficiency (>90 %) was obtained in a wide potential window from −0.8 to −1.2 V RHE. [ABSTRACT FROM AUTHOR]

Electrocatalytic conversion of carbon dioxide to valuable chemicals and fuels driven by renewable energy plays a crucial role in achieving net-zero carbon emissions. Understanding the structure-activity relationship and the reaction mechanism is significant for tuning electrocatalyst selectivity. Therefore, characterizing catalyst dynamic evolution and reaction intermediates under reaction conditions is necessary but still challenging. We first summarize the most recent progress in mechanistic understanding of heterogeneous CO 2 /CO reduction using in situ/operando techniques, including surface-enhanced vibrational spectroscopies, X-ray- and electron-based techniques, and mass spectroscopy, along with discussing remaining limitations. We then offer insights and perspectives to accelerate the future development of in situ/operando techniques.

Electrochemical synthesis in molten salts has great possibilities for the production of various carbonaceous materials (graphite, graphene, ultra-fine amorphous carbon, doped and undoped carbon nanotubes and fibers) in one step in the form of films and ultra-fine powders. Carbon dioxide dissolved in molten salts under excess pressure can be a carbon precursor during the synthesis. The peculiarities of electrochemical reduction of carbon in solid state from CO 2 were studied by cyclic votammetry. The mechanisms of cathodic and anodic processes were suggested. The conditions (composition of electrolytic bath, temperature, cathodic current density, bath potential) of electrochemical synthesis of nanoscale carbon materials were determined. The properties of the produced carbon-containing products were analyzed by XRD, SEM, TEM, ED, Raman spectroscopy. A correlation of product properties with synthesis conditions and parameters has been made. [ABSTRACT FROM AUTHOR]

Here we review recent developments and technological advances in the field of electrochemical reduction of carbon dioxide to fuels, energy carriers and precursors and other interesting building blocks for industrial applications. Synthetic hydrocarbon fuels derived from CO2/H2O are proposed as alternatives to hydrogen as an energy carrier that enables a carbon-neutral energy cycle, given their inherent advantages of high H/C ratio and convenience of storage and transportation. The electrochemical reduction of CO2 represents a feasible route for the direct generation of hydrocarbon fuels or their precursors (i.e., synthesis gas) using CO2/H2O. Such hydrocarbons fit well within the existing energy infrastructure because of their similarity to existing fossil fuels. Recently significant efforts are being devoted to the development of prototype systems, such as low- or high- temperature electrolyzers that operate as part of environmentally sustainable energy networks. [ABSTRACT FROM AUTHOR]

Novel hierarchical copper oxide (Cu X O) nanosphere particles are synthesized, and then coated onto gas diffusion layer (carbon) to form a working electrode for catalyzing CO 2 electroreduction. When applying a negative voltage to the working electrode, the metal Cu nanoparticles which are induced by the Cu X O nanospheres appear. Cu X O and metal Cu together form the Cu X O/Cu nanocatalysts which show high catalytic activity for CO 2 electroreduction. The morphology, composition, crystal structure and surface area of the Cu X O/Cu electrocatalysts are characterized using scanning electron microscopy, X-ray diffraction, and X-ray photoelectron spectroscopy. The Cu X O/Cu nanoparticles are tested as the catalysts for CO 2 electroreduction using cyclic voltammetry and linear sweep voltammetry in CO 2 -saturated 0.5 M KHCO 3 aqueous electrolyte. It is found that the CO 2 electroreduction activity is highly improved using this Cu X O/Cu nanocatalyst, which remains stable during 20 h of electrolysis, along with the high selectivity with a ∼62% of Faradaic efficiency for formate production. Detailed kinetic information relevant to the catalysis is also discussed. [ABSTRACT FROM AUTHOR]

Abstract: We have investigated the CO2 electroreduction at a Pt–Ru/C-based catalyst using a membrane electrode assembly (MEA) in a single cell to realize a methanol-based reversible fuel cell. Cyclic voltammograms were measured under N2 and CO2 atmospheres using the Pt–Ru/C-based MEA. For comparison, the Pt/C-based MEA was used. A typical voltammogram attributed to the Pt electrode has been obtained using Pt/C under an N2 atmosphere, and an extra oxidation peak appeared at 0.60 V vs. DHE under a CO2 atmosphere. This peak has been considered to be caused by the re-oxidation of the CO2 reductant. For the Pt–Ru/C, the re-oxidation peak has been observed at 0.50 V vs. DHE which is more negative than Pt/C. The limiting cathode potential of the cyclic voltammogram was changed from 0.06 to 0.35 V vs. DHE under a CO2 atmosphere, and the magnitude of the re-oxidation peak decreased. To quantitatively analyze the product of the CO2 reduction, a gas chromatograph and methanol- and CO-stripping voltammograms were measured. Based on these results, methanol has been found to be the main product of the CO2 reduction at the Pt–Ru/C. Finally, the methanol yield and coulombic efficiency were calculated resulting in 7.5% and 75% at the Pt–Ru/C, respectively. [Copyright &y& Elsevier]

Abstract: In this study, we investigated the viability of a reversible fuel cell which uses methanol as the candidate liquid fuel. This fuel cell consists of methanol oxidation and its coupled carbon dioxide (CO2) reduction reaction. The CO2 electrode reaction using a membrane electrode assembly (MEA) with a carbon-supported platinum (Pt/C)-based anode and cathode was evaluated. First, the electrode potential of the CO2 reduction at the MEA cathode was measured by linear sweep voltammetry. The resulting voltammograms show that the CO2 reduction occurs within the electrode potential region of 0.06–0.4 V vs. the dynamic hydrogen electrode (DHE) in a CO2 atmosphere. Products of the CO2 electrode reaction were then analyzed by gas chromatograph–mass spectrometry, and a small amount of methanol was detected. Stripping voltammetry for CO and methanol was conducted, revealing that CO2 is reduced to methanol and almost all of it strongly adsorbs onto the Pt/C cathode. Finally, the CO2 electroreduction was shown to occur with a relatively high Coulombic efficiency of 30–50% at 0.06–0.25 V vs. DHE. Our study showed that the CO2 reduction was able to produce methanol in an MEA with Pt/C electrodes, which may have applications in future fuel cell development. [Copyright &y& Elsevier]

CO 2 electrolysis in acid has emerged as a promising route to achieve high CO 2 utilization due to the inhibition of undesired carbonate formation that generally occurs in alkaline or neutral conditions. However, the efficiency and stability of this system need to be further improved through tailoring of the electrocatalyst and its working environment. Here, a working microenvironment of structurally engineered NiNC catalyst for acidic CO 2 electrolysis is probed and optimized by adding hydrophobic poly(tetrafluoroethylene) (PTFE) nanoparticles in the catalytic layer of gas-diffusion electrodes. The PTFE-modified electrode delivers nearly 100% CO Faradaic efficiency at an industry-relevant current density of 250 mA cm -2 , and a high single-pass CO 2 utilization of 75.7% at a current density of 200 mA cm -2 under 20 sccm CO 2 gas flow rate. Moreover, compared to a conventional electrode without added PTFE, the PTFE-modified electrode exhibits a substantially enhanced water-flooding-resistant ability. Mechanistic investigations reveal that a moderate PTFE modification can optimize the local CO 2 /H 2 O ratio in the catalytic layer, favoring the reduction of the diffusion layer thickness and the formation of a highly active and stable solid-liquid-gas interfacial microenvironment., (© 2022 Wiley-VCH GmbH.)

[Display omitted] • A high formate Faradaic efficiency of 93.22% has been achieved. • The multi-layer structure realizes the effective reversibility of Sn species. • Multi-layer SnO x remains durable over 40 h electrocatalysis for at least 5 recycles. In this study, a multi-layer SnO x structure was prepared by a ligand-confined growth strategy via the hydrothermal synthesis in the presence of n -butylamine and H 2 O. At an optimized proportion of n-butylamine and H 2 O (volume ratio of 1:1), the SnO x (1:1) catalyst exhibited a high formate Faradaic efficiency of 93.2% and remained durable over 40 h electrocatalysis at −1.15 V vs. RHE for at least 5 recycles. The multi-layer SnO x by means of reduction from Sn(IV) to Sn(II) species, which polarized CO 2 and undergone a protoncoupled electron transfer to gain formate. Moreover, the specific multi-layer structure could stabilize the formation of Sn(II) species to achieve a highly stable selectivity of formate. With the loss of a relatively negative potential, the activated Sn(II) state was spontaneously oxidized to Sn(IV) species on the surface of catalyst. The effective reversibility of the Sn(II) and Sn(IV) species maintained the reproducibility for electrocatalytic CO 2 reduction. [ABSTRACT FROM AUTHOR]

• The corresponding mathematical model is constructed on the basis of experiment. • The reduction capacity of biocatalyst reaches its maximum at −0.8 V and 10-3S/m. • When the biofilm porosity is 0.35, the system reaches the best running state. • The distribution of the product spreads from the plate to the periphery. • The increasing rate of product concentration decreases after increases with time. Microbial electrochemical system (MES) is a favorable tool for CO 2 emission reduction. Microbial cathode is one of the core components of the system, and its surface energy transfer characteristics can greatly affect the yield of organic matter from MES. In order to solve the problem that the energy transfer characteristics of microbial cathode are not clear, the mathematical model of MES was constructed on the basis of the preliminary experiment with an electrode made of copper foam modified with the reduced graphene oxide, analyzing the current and substrate concentration in the biofilm with conductivity, cathode potential and porosity of the biofilm. The results show that when the cathode potential is higher than −0.8 V (VS SHE), the substrate concentration and current density in the biofilm are related to the cathode potential. However, when the cathode potential decreased to −0.8 V (vs SHE), the ability of biofilm to reduce CO 2 basically reached saturation. Low conductivity (<10-3S/m) will lead to the formation of significant potential difference in the biofilm, which will reduce the substrate utilization rate and seriously affect the performance of microbial cathode. The current density is highest, when the porosity of the biofilm is about 0.35. [ABSTRACT FROM AUTHOR]

Bimetallic catalysts catalyst was potential catalyst for electrochemical reduction of CO 2 (CO 2 RR) to produce liquid fuel. Adjusting the adsorption energy of intermediates on bimetallic catalysts was very effective to improve the selectivity of electroreduction of CO 2 to low-carbon alcohols. However, it was difficult to further increase the yield of low-carbon alcohols by adjusting the content ratio between metals alone. Here, in vacuum environment, we use low temperature plasma technology to treat Ag@Cu catalyst to form Cu–CuO interface on the catalyst surface, so that the selectivity and activity of the reaction were further enhanced. The performance of CO 2 RR was effectively improved by the surface Cu–CuO interface. CO 2 RR tests show that at −0.8 V vs RHE, the faraday efficiency of low-carbon alcohols of Ag@Cu-10 catalyst was the highest of 65.5%, which was 19.9% higher than that of Ag@Cu. In addition, the linear sweep voltammetry test showed that the current density of CO 2 RR increased by 2 times, indicating that the surface Cu–CuO interface promoted the activation of CO 2 on the surface of the catalyst and improved the intrinsic activity. This work introduces a technique of preparing surface Cu–CuO interface to adjust the adsorption energy of CO 2 RR intermediates, which provides a new idea for the development of efficient CO 2 RR catalysts. • Surface Cu-CuO interface was prepared to improve the electrocatalytic activity of CO 2. • Ag@Cu exhibited excellent performance for CO 2 RR to low-carbon alcohols with FE of 65.5% at -0.8 V (vs. RHE) and current density of 13 mA·cm-2. • The synergistic effect of Ag and CuO promoted the adsorption of intermediate species. [ABSTRACT FROM AUTHOR]

This article presents a mathematical model that predicts the chemical conditions at the electrode surface during the electrochemical reduction of CO2. Such electrochemical reduction of CO2 to valuable products is an area of interest for the purpose of reducing green house gas emissions. In the reactions involved, CO2 acts as both a reactant and a buffer, consequently the estimation of local concentrations at the electrode surface is not trivial and a numerical approach is required. The necessary partial differential equations (PDEs) have been set-up and solved using MATLAB. The results show the local concentrations at the electrode surface to be significantly different from the bulk concentrations under typical reported experimental conditions. The importance of buffer strength and a careful quantification of the degree of mixing produced in the experimental apparatus is demonstrated. The model has also been used to re-examine previously published data, showing that the Tafel slopes in CO2 reduction are consistent with those reported for the simpler CO reduction system. Further, the effect of pulsed electroreduction was also modeled, showing that pulsing causes corresponding swings in local pH and CO2 concentrations. [ABSTRACT FROM AUTHOR]

Carbon dioxide (CO 2 ) electroreduction can offer a way of relieving environmental and energy issues. Gold and silver catalysts show considerable electrochemical performance for CO production; however, the electrochemical CO 2 conversion to CO is still restricted by the Faradaic efficiency, current density, and stability over the catalysts. Non-noble metal (zinc) is considered as a promising catalyst for CO 2 electroreduction because of its low cost. However, because of the electron-rich property of zinc, it has a weak adsorption capacity of intermediates, resulting in a poor CO 2 electroreduction performance. In this work, ZnS nanoparticles are embedded onto the ZnO surface to construct a stable ZnS/ZnO interface structure. The ZnS/ZnO interface reaches a maximum current density of 327.2 ± 10.6 mA cm -2 with a CO Faradaic efficiency of 91.9 ± 0.6% at -0.73 V vs a reversible hydrogen electrode (RHE) and remains stable for 40 h at a current density of 115.7 ± 7.0 mA cm -2 with a CO Faradaic efficiency of 93.8 ± 3.7% at -0.56 V vs RHE.

[Display omitted] • We put forward a strategy to in situ reconstruct a heterogeneous Ag 2 S/Ag interface structure. • The Ag 2 S/Ag catalyst achieves a high current density of 421.7 ± 14.4 mA cm–2 at –0.70 V vs. reversible hydrogen electrode. • The in situ reconstructive Ag 2 S/Ag interface active sites stabilize the *COOH intermediate. Electrochemical CO 2 reduction reaction (CO 2 RR) offers an appealing route to simultaneously store intermittent renewable energy as value-added chemicals and close carbon cycle. Silver (Ag) catalyst is a promising candidate for the electrochemical conversion of CO 2 to CO, but the electrocatalytic properties are still insufficient for practical applications. Herein, we put forward a strategy to in situ reconstruct a heterogeneous Ag 2 S/Ag interface structure, in which their strong interactions facilitate CO 2 RR performance. The in situ reconstructive Ag 2 S/Ag catalyst achieves a large current density of 421.7 ± 14.4 mA cm–2 at –0.70 V vs. reversible hydrogen electrode (RHE) and maintains steadily at a current density of 244.5 ± 31.8 mA cm–2 and CO Faradaic efficiency of 99.1 ± 0.8 % at –0.49 V vs. RHE for 50 h, superior to state-of-the-art CO-selective Ag-based catalysts. Density functional theory calculations reveal that the in situ reconstructive Ag 2 S/Ag interface active sites stabilize the *COOH intermediate during CO 2 RR process. [ABSTRACT FROM AUTHOR]

Catalytic electroreduction of carbon dioxide represents a promising technology both to reduce CO2 emissions and to store electrical energy from discontinuous sources. In this work, electrochemical deposition of copper on to a gas-diffusion support was tested as a scalable and versatile nanosynthesis technique for the production of catalytic electrodes for CO2 electroreduction. The effect of deposition current density and additives (DAT, DTAB, PEG) on the catalysts' structure was evaluated. The selectivity of the synthesized catalysts towards the production of CO was evaluated by analyzing the gaseous products obtained using the catalysts as cathodes in electroreduction tests. Catalyst morphology was deeply influenced by the deposition additives. Copper nanospheres, hemispherical microaggregates of nanowires, and shapeless structures were electrodeposited in the presence of dodecyltrimethylammonium bromide (DTAB), 3,5-diamino-1,2,4-triazole (DAT) and polyethylene glycol (PEG), respectively. The effect of the deposition current density on catalyst morphology was also observed and it was found to be additive-specific. DTAB nanostructured electrodes showed the highest selectivity towards CO production, probably attributable to a higher specific surface area. EDX and XPS analysis disclosed the presence of residual DAT and DTAB uniformly distributed onto the catalysts structure. No significant effects of electrodeposition current density and Cu(I)/Cu(II) ratio on the selectivity towards CO were found. In particular, DTAB and DAT electrodes yielded comparable selectivity, although they were characterized by the highest and lowest Cu(I)/Cu(II) ratio, respectively. [ABSTRACT FROM AUTHOR]

[Display omitted] • Single-atom Co based dual-site catalyst is constructed. • N- and CoN 3 -anchored CoPc have distinct active for CO 2 RR and HER. • Distinct interaction of CoPc and anchored sites govern their catalytical ability. • Syngas with ideal H 2 /CO ratio is produced with industrial current density. • Syngas also produced by a Zn−CO 2 battery at high discharging current density. Dual single-cobalt atom-based catalysts were synthesized using CoN 3 sites and N dopants co-decorated hierarchically porous carbon (HPC-Co) as the matrix to immobilize cobalt phthalocyanine (CoPc). CoPc interacts with N dopants and CoN 3 , forming N-CoPc and CoN 3 -CoPc sites via π–π and Co-Co interactions. HPC-Co/CoPc (5:1) produced syngas at industrial current densities (> 200 and 880 mA cm−2 for the H-type and flow cell, respectively). Rechargeable Zn-CO 2 batteries based on this catalyst had current densities of 7 and 10 mA cm−2 at ideal H 2 /CO ratios of 2 and 3, respectively. The efficient production of syngas is attributed to synergistic catalysis between N-CoPc (for CO 2 reduction) and CoN 3 -CoPc (for hydrogen evolution). This work presents a versatile strategy for the synthesis of dual single-atom-based carbon electrocatalysts for efficient conversion of CO 2 to syngas. This strategy is superior to conventional high-temperature pyrolysis that is difficult to control the atomic dispersion of distinct metal sites. [ABSTRACT FROM AUTHOR]

• Manganese organometallic electrochemically converts CO 2 into CO in complete PEM cell. • Gas-fed complete flow cell promotes mass transport and electrochemical activity. • Gas diffusion layer covalently grafted organometallic complex employed in gas phase. • Non-precious metal based scalable electrochemical CO 2 conversion microreactor. The electrochemical reduction of carbon dioxide (CO 2 RR) is a viable route for the transformation of intermittent renewable energy into high energy density chemical vectors (e.g. CO) or into fuels. Differently from metal nanoparticle electrocatalysts, the use of organometallic molecular complexes affords more efficient metal utilization, limits poisoning phenomena and allows the tuning of selectivity by varying the electronic and coordination properties of the metal center. Herein the organometallic complex (fac -Mn(apbpy)(CO) 3 Br) (apbpy = 4-(4-aminophenyl)-2,2′-bipyridine) was covalently anchored on a gas diffusion layer which was further employed as cathode in an aqueous gas–liquid interface complete electrolysis flow cell microreactor. The decorated gas diffusion layer electrode was able to convert CO 2 into CO and HCOOH with faradaic efficiencies (FE) of 76% and 10% with a CO-productivity close to 70 Nl min−1 g Mn −1 reaching CO 2 RR turnover numbers up to 1.6·105. This result largely outperforms a state-of-the-art gold nanoparticle electrocatalyst (Au/C 10 wt%) operating in the same cell conditions. [ABSTRACT FROM AUTHOR]

Reaction temperature is an important parameter to tune the selectivity and activity of electrochemical CO 2 reduction reaction (CO 2 RR) due to different thermodynamics of CO 2 RR and competitive hydrogen evolution reaction (HER). In this work, temperature-dependent CO 2 RR over Fe-N-C and Ni-N-C single-atom catalysts are investigated from 303 to 343 K. Increasing the reaction temperature improves and decreases CO Faradaic efficiency over Fe-N-C and Ni-N-C catalysts at high overpotentials, respectively. CO current density over Fe-N-C catalyst increases with temperature, then gets into a plateau at 323 K, finally reaches the maximum value of 185.8 mA cm -2 at 343 K. While CO current density over Ni-N-C catalyst achieves the maximum value of 252.5 mA cm -2 at 323 K, and then drops significantly to 202.9 mA cm -2 at 343 K. Temperature programmed desorption results and density functional theory calculations reveal that the difference of temperature-dependent variation on CO Faradaic efficiency and current density between Fe-N-C and Ni-N-C catalysts results from the varied adsorption strength of key reaction intermediates during CO 2 RR., (© 2021 Wiley-VCH GmbH.)

Mn-C 3 N exhibits high catalytic activity and selectivity for CO 2 hydrogenation into HCOOH, due to its low limiting potential (−0.24 V) and low energy barrier (0.75 eV). • A series of transition metal doped C 3 N monolayer (M-C 3 N) has been investigated based on the DFT method. • M-C 3 N (M=Mn, Fe, Ru, Rh) were screened out as the promising CO 2 ER catalyst. • The hydrogen evolution is suppressed on Mn-C 3 N surface. • Mn-C 3 N exhibits high catalytic activity and selectivity for reduction CO 2 to HCOOH. Recently, two-dimensional graphitic carbon nitrides have emerged as potential electrocatalysts for CO 2 electroreduction (CO 2 ER). Herein, a series of transition metal (M = Mn-Cu, Ru-Ag) doped C 3 N monolayer (M-C 3 N) as a novel CO 2 ER catalyst has been investigated by employing the density functional method. By a careful computational screening, Mn-C 3 N is identified as the best catalyst for CO 2 ER, due to its high catalytic activity and high selectivity. HCOOH is the final product with a low overpotential of 0.04 V and a low kinetic energy barrier of 0.75 eV. The hydrogen evolution is also suppressed on Mn-C 3 N surface. Therefore, the CO 2 ER activity could be tuned by adjusting the metal atom in the C 3 N monolayer, which may shed new light on designing novel C 3 N-based CO 2 ER catalyst. [ABSTRACT FROM AUTHOR]

A solid oxide cell (SOC) integrating solid oxide fuel cell (SOFC) and solid oxide electrolysis cell (SOEC) usually utilizes two different materials as the anode and cathode prepared by the costly multi-elements co-doping process. In this work, LaCo 0.6 Ni 0.4 O 3−δ (LCN) is employed as the contact material and the electrode for the symmetrical SOC and exhibits good catalytic activities towards the four typical reactions, i.e., oxygen reduction reaction (ORR), hydrogen oxidation reaction (HOR), oxygen evolution reaction (OER), and CO 2 reduction reaction (CO 2 RR). The LCN-GDC electrode has the low activation energies of 1.18 and 0.55 eV as the cathode and anode of SOFC, respectively. High peak power densities (PPDs) of 1.896 and 0.562 W cm−2 are obtained at 800 °C for the Ni-YSZ (8 mol.% Y 2 O 3 stabilized ZrO 2) anode-supported and YSZ (200 μm)-supported symmetrical SOFCs, respectively. An electrolysis current density (ECD) of 2.316 A cm−2 is obtained at 800 °C and 2.0 V and a robust operation for over 120 h with a degradation rate of about 0.5 mV h−1 is achieved with LCN as the current collector in air side at 750 °C for the symmetrical SOECs. Such a multi-functional material shows attractive competitiveness and successfully achieves fivefold applications in SOCs. The protocol described herein affords a new vision towards material development basing on the consideration of enhancing the chemical compatibility and lowering the cost of the whole SOC but not just one electrode. We report the successful fivefold applications of the multi-functional LaCo 0.6 Ni 0.4 O 3-δ in solid oxide cells for the multipurpose scenarios basing on the perceptively and integrally consideration of enhancing the chemical compatibility and lowering the fabrication cost of the whole integrated solid oxide device but not just one electrode. Image 1 • LCN is employed as electrodes to enhance the compatibility and lower the cost of the whole SOC but not just one component. • The fivefold applications of LCN benefit from its high conductivity and phase diversity against atmospheres. • LCN-GDC has small activation energies of 1.18 and 0.55 eV as the cathode and anode of SOFC, respectively. • PPDs of 1.896 and 0.562 W cm−2 are obtained at 800 °C for the anode-supported and symmetrical SOFCs, respectively. • An ECD of 2.316 A cm-2 at 800 °C and 2.0 V and good stability of over 120 h are obtained for the symmetrical SOECs. [ABSTRACT FROM AUTHOR]

Electrochemical energy storage and conversion is an effective strategy to relieve the increasing energy and environment crisis. The sluggish reaction kinetics in the related devices is one of the major obstacles for them to realize practical applications. More efforts should be devoted to searching for high-efficiency electrocatalysts and enhancing the electrocatalytic performance. 3D graphene macrostructures (3D GMs) are one kind of porous crystalline materials with 3D structures at both micro- and macro-scale. The unique structure can achieve large accessible surface area, expose many active sites, promote fast mass/electron transport, and provide wide room for further functional modification. All these features make them promising candidates for electrocatalysis. In this review, the authors focus on the latest progress of 3D GMs for electrocatalysis. First, the preparation methods of 3D GMs are introduced followed by the strategies for functional modifications. Then, their electrocatalytic performances are discussed in detail including monofunctional and bifunctional electrocatalysis. The electrocatalytic processes involve oxygen reduction reaction, oxygen evolution reaction, hydrogen evolution reaction, and carbon dioxide reduction reaction. Finally, the challenges and perspectives are presented to offer a guideline for the exploration of excellent 3D GM-based electrocatalysts., (© 2021 Wiley-VCH GmbH.)

Electroreduction of CO 2 into carbonaceous fuels or industrial chemicals using renewable energy sources is an ideal way to promote global carbon recycling. Thus, it is of great importance to develop highly selective, efficient, and stable catalysts. Herein, we prepared cobalt single atoms (Co SAs) coordinated with phthalocyanine (Co SAs-Pc). The anchoring of phthalocyanine with Co sites enabled electron transfer from Co sites to CO 2 effectively via the π-conjugated system, resulting in high catalytic performance of CO 2 electroreduction into CO. During the process of CO 2 electroreduction, the Faradaic efficiency (FE) of Co SAs-Pc for CO was as high as 94.8 %. Meanwhile, the partial current density of Co SAs-Pc for CO was -11.3 mA cm -2 at -0.8 V versus the reversible hydrogen electrode (vs RHE), 18.83 and 2.86 times greater than those of Co SAs (-0.60 mA cm -2 ) and commercial Co phthalocyanine (-3.95 mA cm -2 ), respectively. In an H-cell system operating at -0.8 V vs RHE over 10 h, the current density and FE for CO of Co SAs-Pc dropped by 3.2 % and 2.5 %. A mechanistic study revealed that the promoted catalytic performance of Co SAs-Pc could be attributed to the accelerated reaction kinetics and facilitated CO 2 activation., (© 2020 Wiley-VCH GmbH.)

A copper‐oxide‐based catalyst enriched with paramelaconite (Cu4O3) is presented and investigated as an electrocatalyst for facilitating electroreduction of CO2 to ethylene and other hydrocarbons. Cu4O3 is a member of the copper‐oxide family and possesses an intriguing mixed‐valance nature, incorporating an equal number of Cu+ and Cu2+ ions in its crystal structure. The material is synthesized using a solvothermal synthesis route and its structure is confirmed via powder X‐ray diffraction, transmission electron microscope based selected area electron diffraction, and X‐ray photoelectron spectroscopy. A flow reactor equipped with a gas diffusion electrode is utilized to test a copper‐based catalyst enriched with the Cu4O3 phase under CO2 reduction conditions. The Cu4O3‐rich catalyst (PrC) shows a Faradaic efficiency for ethylene over 40% at 400 mA cm−2. At −0.64 versus reversible hydrogen electrode, the highest C2+/C1 product ratio of 4.8 is achieved, with C2+ Faradaic efficiency over 61%. Additionally, the catalyst exhibits a stable performance for 24 h at a constant current density of 200 mA cm−2. [ABSTRACT FROM AUTHOR]

Nanostructure and crystallinity of transition metals play an important role in catalyzing carbon dioxide electroreduction (CO2ER) where Cu is a typical electrocatalyst with a wide variety of products and Pb has a high overpotential for H2 evolution and is selective toward formic acid. In this study, 3D hierarchical nanostructures of Cu–Pb catalyst are prepared by a two‐step electrodepositing–annealing–electroreduction approach (EAE). Cu nanowires (Cu NWs) of 200–400 nm diameter are built on the surface of commercial nickel foam substrates through an EAE step. Then, Pb nanoparticles with diameter of 5–10 nm are uniformly created on the surface of Cu NWs by a second EAE step. The nanostructural Cu–Pb electrodes catalyze CO2ER at a current density of −9.35 mA cm−2 (at −0.93 V vs reversible hydrogen electrode (RHE)). The H2 evolution is suppressed by 35.6% and CO and HCOOH are enhanced by 29.6% and 9.2%, respectively, as compared with Cu NWs. The protocol proposed in this study provides a simple and straightforward approach for preparing high‐performance, hierarchical nanostructures of Cu–Pb bimetal catalyst for CO2ER. A two‐step electrodepositing‐annealing‐electroreduction approach is developed to synthesize 3‐dimensional hierarchical nanostructures of Cu‐Pb catalysts, which catalyze CO2 electroreduction in bicarbonate solutions at a current density of –9.35 mA cm–2 and faradaic efficiencies of 50.64% and 21.97% for CO and HCOOH. The protocol provides a straightforward approach for preparing high‐performance, hierarchical nanostructures of Cu‐Pb bimetal catalyst for CO2 electroreduction. [ABSTRACT FROM AUTHOR]

Simultaneously achieving high Faradaic efficiency, current density, and stability at low overpotentials is essential for industrial applications of electrochemical CO 2 reduction reaction (CO 2 RR). However, great challenges still remain in this catalytic process. Herein, a synergistic catalysis strategy is presented to improve CO 2 RR performance by anchoring Fe-N sites with cobalt phthalocyanine (denoted as CoPc©Fe-N-C). The potential window of CO Faradaic efficiency above 90% is significantly broadened from 0.18 V over Fe-N-C alone to 0.71 V over CoPc©Fe-N-C while the onset potential of CO 2 RR over both catalysts is as low as -0.13 V versus reversible hydrogen electrode. What is more, the maximum CO current density is increased ten times with significantly enhanced stability. Density functional theory calculations suggest that anchored cobalt phthalocyanine promotes the CO desorption and suppresses the competitive hydrogen evolution reaction over Fe-N sites, while the *COOH formation remains almost unchanged, thus demonstrating unprecedented synergistic effect toward CO 2 RR., (© 2019 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

The electroreduction of carbon dioxide (CO 2 ) toward high-value fuels can reduce the carbon footprint and store intermittent renewable energy. The iodide-ion-assisted synthesis of porous copper (P-Cu) microspheres with a moderate coordination number of 7.7, which is beneficial for the selective electroreduction of CO 2 into multicarbon (C 2+ ) chemicals is reported. P-Cu delivers a C 2+ Faradaic efficiency of 78 ± 1% at a potential of -1.1 V versus a reversible hydrogen electrode, which is 32% higher than that of the compact Cu counterpart and approaches the record (79%) reported in the same cell configuration. In addition, P-Cu shows good stability without performance loss throughout a continuous operation of 10 h., (© 2019 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Electrochemical reduction of CO 2 (ERC) to useful chemicals is an environmentally and technologically significant process. The process is confronted with significant challenges to simultaneously enhance the catalyst activity and product selectivity. In this paper, the effects of organic additives on the ERC process were systematically investigated by using DFT to screen additives with different functional groups for enhanced activity and selectivity. In particular, the additives with -NH 3 + and -SO 3 H groups had a remarkably positive effect on the ERC activity and hydrocarbon selectivity, which were predicted to impart a positive shift on onset potential of approximately 162 and 108 mV, respectively. Importantly, the additive can accelerate the electron transfer of the intermediate and tune the electronic structure of the catalyst surface, resulting in a clear deviation from transition-metal scaling lines. Combining bonding energy of crucial intermediates with partial atomic charge analysis, we rationalized the negative effect of high concentration additives and confirmed the proposed electron transfer model. Furthermore, additive molecules containing functional groups with positive charges and maximizing the deviation from transition-metal scaling lines are meaningful strategies to design and choose organic additives to enhance activity and selectivity of ERC., (© 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

As synthetic methods advance for metal nanoparticles, more rigorous studies of structure-function relationships can be made. Many electrocatalytic processes depend on the size, shape, and composition of the nanocatalysts. Here, the properties and electrocatalytic behavior of random alloyed and intermetallic nanoparticles are compared. Beginning with an introduction of metallic nanoparticles for catalysis and the unique features of bimetallic compositions, the discussion transitions to case studies of nanoscale electrocatalysts where direct comparisons of alloy and intermetallic compositions are undertaken for methanol electrooxidation, formic acid electrooxidation, the oxygen reduction reaction, and the electroreduction of carbon dioxide (CO 2 ). Design and synthesis strategies for random alloyed and intermetallic nanoparticles are discussed, with an emphasis on Pt-M and Cu-M compositions as model systems. The differences in catalytic performance between alloys and intermetallic nanoparticles are highlighted in order to provide an outlook for future electrocatalyst design., (© 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

The conversion efficiency and product selectivity of the electroreduction of carbon dioxide have been largely limited by the low CO 2 solubility in aqueous solution. To relieve this problem, Cu 3 (BTC) 2 (Cu-MOF) as CO 2 capture agent was introduced into a carbon paper based gas diffusion electrode (GDE) in this study. The faradaic efficiencies (FEs) of CH 4 on GDE with Cu-MOF weight ratio in the range of 7.5-10% are 2-3-fold higher than that of GDE without Cu-MOF addition under negative potentials (-2.3 to -2.5 V vs SCE), and the FE of the competitive hydrogen evolution reaction (HER) is reduced to 30%. This work paves the way to develop GDE with high catalytic activity for ERC.

Carbon dioxide electroreduction to chemicals and fuels powered by renewable energy sources is considered a promising path to address climate change and energy storage needs. We have developed highly active and selective copper (Cu) nanocube catalysts with tunable Cu(100) facet and oxygen/chlorine ion content by low-pressure plasma pretreatments. These catalysts display lower overpotentials and higher ethylene, ethanol, and n-propanol selectivity, resulting in a maximum Faradaic efficiency (FE) of ∼73% for C 2 and C 3 products. Scanning electron microscopy and energy-dispersive X-ray spectroscopy in combination with quasi-in situ X-ray photoelectron spectroscopy revealed that the catalyst shape, ion content, and ion stability under electrochemical reaction conditions can be systematically tuned through plasma treatments. Our results demonstrate that the presence of oxygen species in surface and subsurface regions of the nanocube catalysts is key for achieving high activity and hydrocarbon/alcohol selectivity, even more important than the presence of Cu(100) facets.