Review Article
Electrocatalytic CO2 reduction on nanostructured metal-based materials: Challenges and constraints for a sustainable pathway to decarbonization

https://doi.org/10.1016/j.jcou.2021.101579Get rights and content

Highlights

  • Electrocatalysts for electrochemical reduction of CO2.

  • Improving activity and selectivity for production of multi-carbon products.

  • Understanding catalytic mechanisms for advancing catalysts design.

  • Metal-nitrogen carbon catalysts as an efficient alternative to noble metal catalysts.

  • Perspective on the relationship between materials structure, morphology, and activity.

Abstract

The increasing release of carbon dioxide into atmosphere has caused serious environmental consequences and closing the carbon loop is therefore essential for promoting the transition towards a sustainable development. Electrochemical reduction of carbon dioxide (E−CO2RR) represents a powerful strategy for reducing CO2 levels in atmosphere and obtaining value-added chemicals and fuels using renewable energy sources. Despite the important achievements obtained so far, major issues associated with activity and selectivity of electrocatalysts toward the production of multi-carbon (C2+) products hinder large-scale applications. Hence, a thorough understanding of catalytic mechanisms is needed for advancing the design of efficient electrocatalysts to drive the reaction pathway to the desired products. This review summarizes the latest advances in the design of nanostructured metal-based catalysts for E−CO2RR, with a special emphasis on the synthesis procedures and electrochemical performance of metal-nitrogen-carbon catalysts. An overview on the catalytic mechanisms is included along with a discussion of the experimental and computational techniques for mechanistic studies and catalyst development. Finally, we outline a perspective on the relationship between structure, morphology and electrochemical activity highlighting challenges and outlook on developing metal-nitrogen-carbon electrocatalysts for E−CO2RR to multi-carbon products.

Introduction

The concentration of carbon dioxide in the atmosphere is increasing very fast, due to anthropogenic activities, such as combustion of fossil fuels from industrial processes and transportation. CO2 greatly contributes to greenhouse gas emissions, being the main driver of global warming. To promote the sustainable development of the planet, the Intergovernmental Panel on Climate Change recently recommended to limit global warming to 1.5 degrees Celsius, rather than the previous threshold of 2, requiring governments to take actions to limit carbon emission [1,2]. As a key objective of the European Green Deal and in line with the EU’s commitment to global climate action under the Paris Agreement, the EU aims to be climate-neutral by 2050, adopting an economy with net-zero greenhouse gas emissions [3]. The carbon capture and storage (CCS) is considered as a viable strategy to decrease CO2 emissions. Despite the extensive global efforts in the past two decades, large-scale development of CCS is slow, due to long-term-storage issues related to gaseous CO2 leakage [4]. The carbon dioxide reduction reaction (CO2RR) that transforms CO2 into different value-added carbon-based compounds is an alternative strategy to CCS, not only allowing the mitigation of CO2 emission but also producing useful chemicals, such as CH3OH, CH4, CO, and HCOOH which can be used as fuels [[5], [6], [7], [8], [9], [10]].

CO2RR can be achieved by using different approaches, such as biochemical, thermochemical, photochemical, and electrochemical methods, achieving high energy efficiency, high reaction rates, and high value products [[11], [12], [13], [14]]. The efforts of the academic community on improving productivity, stability, and environmental friendliness of processes while reducing costs have gradually increased since mid-2010, leading to an exponential increase of the number of publications dealing with CO2RR, as indicated in Fig. 1.

Among these methods, electrochemical CO2 reduction reaction (E−CO2RR) technique provides several advantages, including controllable reaction steps, relatively mild conditions, and good conversion efficiency. In addition, the drive power of E−CO2RR can be efficiently and sustainably harvested from renewable energy sources, such as wind, solar, and hydroelectric energy. This could potentially close the carbon loop and simultaneously address the issues of global warming and energy crisis. Exhaustive reviews addressing E−CO2RR process from a both mechanistic/theoretical perspective and technology development have been published in 2020–2021 [[15], [16], [17], [18], [19], [20], [21]].

Although the faradaic efficiency can exceed 90 %, a poor long-term stability is a bottleneck of this technology, which can be addressed by fabricating highly efficient catalysts with high stability for industrial application [22,23]. Nanostructured metal-based electrocatalysts with tuned morphology, controlled composition, and tailored active sites have achieved satisfactory catalytic activity for CO2 reduction; however, stability issues are still challenging and the real active sites and key factors governing the catalytic performance and the obtained reduction products need to be fully understood.

In this review article we summarize the recent advances in designing various nanostructured metal-based heterogeneous electrocatalysts for E−CO2RR, discussing the reaction mechanism and structure–performance relationship in detail. Challenges and constraints toward controlled synthesis of advanced electrocatalysts are proposed for promoting the development of E−CO2RR as a sustainable path for decarbonization of energy system.

Section snippets

Electrochemical Carbon dioxide reduction reaction (E−CO2RR): fundamental reaction pathways

The electrochemical reduction of carbon dioxide is a powerful strategy for reducing CO2 levels in atmosphere and obtaining fuels using renewable energy [24]. The most common products derived from carbon dioxide reduction in aqueous media are carbon monoxide and formic acid [25], while multi-carbon hydrocarbons and oxygenates (like ethylene, isobutane, ethanol, methanol, acetate, and n-propanol) are more desirable due their higher energy density and wider applicability. However, the commercial

Metal bulk catalysts

Pioneering studies related to CO2 electroreduction report the reaction product distribution achieved by electrocatalysts based on metals such as Hg, Pb, Zn, Cd, Sn, In [42,43], Au, Ag, Cu, Ni and Fe in hydrogencarbonate solution [[43], [44], [45]]. The metals can be divided into five groups, based on their selectivity toward a specific product: i) Hg, Pb, Zn, Cd, Sn, and In predominantly lead to formate (HCO2), ii) Zn leads to formate and CO, iii) Au and Ag yield CO, iv) Cu mostly yields a

Structure-activity relationship of M-N-C heterogeneous catalysts

Recent works provided experimental and theoretical elucidation on the effect of chemical surface, structure, and morphology of M-N-C heterogeneous catalysts on their activity and selectivity towards CO2RR. One of the key features of M-N-C materials which improves selectivity toward CO production as compared to metal bulk catalysts is their nanostructure. As reported by Bagger et al. [135], HER is disadvantaged in this type of material since the atomicaly dispersed active sites are distant,

Conclusions and outlook

The existing challenges for a sustainable pathway to decarbonization has caused a continuing interest in catalyst development for electrochemical reduction of carbon dioxide (E−CO2RR). Among the metal bulk catalysts, Cu has been found the most active metal in CO2 conversion: CO2 can be efficiently reduced to CO or HCOOH, while the formation of C2+ products remains challenging, as highlighted by very recent reviews [[165], [166], [167]]. Rds for CO2 reduction to C2 products is the formation of a

Declaration of Competing Interest

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

References (167)

  • A.S. Varela

    The importance of pH in controlling the selectivity of the electrochemical CO2 reduction

    Curr. Opin. Green Sustain. Chem.

    (2020)
  • C.M. Gabardo et al.

    Continuous carbon dioxide electroreduction to concentrated multi-carbon products using a membrane electrode assembly

    Joule

    (2019)
  • W.H. Lee et al.

    Highly selective and stackable electrode design for gaseous CO2 electroreduction to ethylene in a zero-gap configuration

    Nano Energy

    (2021)
  • J. Wang et al.

    In-Sn alloy core-shell nanoparticles: In-doped SnOx shell enables high stability and activity towards selective formate production from electrochemical reduction of CO2

    Appl. Catal. B Environ.

    (2021)
  • Y. Hori et al.

    Electrochemical reduction of carbon dioxide at various series of copper single crystal electrodes

    J. Mol. Catal. A Chem.

    (2003)
  • J.J. Kim et al.

    Reduction of carbon dioxide and carbon monoxide to methane on copper foil electrodes

    J. Electroanal. Chem. Interfacial Electrochem.

    (1988)
  • Y. Hori et al.

    Electrocatalytic process of CO selectivity in electrochemical reduction of CO2 at metal electrodes in aqueous media

    Electrochim. Acta

    (1994)
  • F. Jia et al.

    Enhanced selectivity for the electrochemical reduction of CO2 to alcohols in aqueous solution with nanostructured Cu-Au alloy as catalyst

    J. Power Sources

    (2014)
  • M. Hammouche et al.

    Catalysis of the electrochemical reduction of carbon dioxide by iron(“0”) porphyrins

    J. Electroanal. Chem. (Lausanne)

    (1988)
  • L. Yoon Suk Lee et al.

    Electrocatalytic reduction of carbon dioxide

    Chem.

    (2017)
  • C.G. Margarit et al.

    Carbon dioxide reduction by Iron hangman porphyrins

    Organometallics

    (2019)
  • M.M. Hossen et al.

    Synthesis and characterization of high performing Fe-N-C catalyst for oxygen reduction reaction (ORR) in Alkaline Exchange Membrane Fuel Cells

    J. Power Sources

    (2018)
  • R. Gokhale et al.

    Direct synthesis of platinum group metal-free Fe-N-C catalyst for oxygen reduction reaction in alkaline media

    Electrochem. Commun.

    (2016)
  • F. Shahbazi Farahani et al.

    Tailoring morphology and structure of manganese oxide nanomaterials to enhance oxygen reduction in microbial fuel cells

    Synth. Met.

    (2020)
  • B. Mecheri et al.

    Facile synthesis of graphene-phthalocyanine composites as oxygen reduction electrocatalysts in microbial fuel cells

    Appl. Catal. B Environ.

    (2018)
  • O. Hoegh-Guldberg et al.

    Achlatis M. Listed as contributing author), chapter 3: impacts of 1.5°C global warming on natural and human systems

    Global Warming of 1.5 °C. An IPCC Special Report on the Impacts of Global Warming of 1.5 °C Above Preindustrial Levels and Related Global Greenhouse Gas Emission Pathways […], Spec. Report, Intergov. Panel Clim. Chang

    (2018)
  • European Commission et al.

    Annex to the european green deal

    Eur. Comm.

    (2019)
  • European Commission

    The european green deal

    Eur. Comm.

    (2019)
  • Y. Song et al.

    Advances in clean fuel ethanol production from electro-, photo-and photoelectro-catalytic co2 reduction

    Catalysts

    (2020)
  • Y. Li et al.

    Boosting thermo-photocatalytic CO2 conversion activity by using photosynthesis-inspired electron-proton-transfer mediators

    Nat. Commun.

    (2021)
  • D. Xue et al.

    Defect engineering on carbon-based catalysts for electrocatalytic CO2 reduction

    Nano-Micro Lett.

    (2021)
  • A. Wagner et al.

    Towards molecular understanding of local chemical environment effects in electro- and photocatalytic CO2 reduction

    Nat. Catal.

    (2020)
  • J. Mukherjee et al.

    Manganese and rhenium tricarbonyl complexes equipped with proton relays in the electrochemical CO2 reduction reaction

    Eur. J. Inorg. Chem.

    (2020)
  • M. Li et al.

    Heterogeneous single-atom catalysts for electrochemical CO2 reduction reaction

    Adv. Mater.

    (2020)
  • S. Popović et al.

    Stability and degradation mechanisms of copper‐based catalysts for electrochemical CO 2 reduction

    Angew. Chem.

    (2020)
  • Z. Chen et al.

    Nanostructured cobalt-based electrocatalysts for CO2 reduction: recent progress, challenges, and perspectives

    Small

    (2020)
  • H. Yang et al.

    Recent progress in self-supported catalysts for CO2 electrochemical reduction

    Small Methods

    (2020)
  • D.T. Whipple et al.

    Prospects of CO2 utilization via direct heterogeneous electrochemical reduction

    J. Phys. Chem. Lett.

    (2010)
  • R. Kortlever et al.

    Catalysts and reaction pathways for the electrochemical reduction of carbon dioxide

    J. Phys. Chem. Lett.

    (2015)
  • D. Gao et al.

    Rational catalyst and electrolyte design for CO2 electroreduction towards multicarbon products

    Nat. Catal.

    (2019)
  • T. Asset et al.

    Investigating the nature of the active sites for the CO2 reduction reaction on carbon-based electrocatalysts

    ACS Catal.

    (2019)
  • A.S. Varela et al.

    Molecular nitrogen–carbon catalysts, solid metal organic framework catalysts, and solid Metal/Nitrogen-Doped carbon (MNC) catalysts for the electrochemical CO2 reduction

    Adv. Energy Mater.

    (2018)
  • F. Zhang et al.

    Rapid product analysis for the electroreduction of co 2 on heterogeneous and homogeneous catalysts using a rotating ring detector

    J. Electrochem. Soc.

    (2020)
  • Y. Yang et al.

    Operando methods in electrocatalysis

    ACS Catal.

    (2021)
  • A.D. Handoko et al.

    Understanding heterogeneous electrocatalytic carbon dioxide reduction through operando techniques

    Nat. Catal.

    (2018)
  • J.H. Baricuatro et al.

    Operando electrochemical spectroscopy for CO on Cu(100) at pH 1 to 13: validation of grand canonical potential predictions

    ACS Catal.

    (2021)
  • A. Herzog et al.

    Operando investigation of Ag-Decorated Cu2O nanocube catalysts with enhanced CO2 electroreduction toward liquid products

    Angew. Chemie - Int. Ed.

    (2021)
  • L. Ma et al.

    Covalent triazine framework confined copper catalysts for selective electrochemical co2 reduction: operando diagnosis of active sites

    ACS Catal.

    (2020)
  • K.K. Patra et al.

    Operando spectroscopic investigation of a boron-doped CuO catalyst and its role in selective electrochemical C−C coupling

    ACS Appl. Energy Mater.

    (2020)
  • T.H. Phan et al.

    Emergence of potential-controlled Cu-Nanocuboids and graphene-covered Cu-Nanocuboids under operando CO2Electroreduction

    Nano Lett.

    (2021)
  • Cited by (33)

    View all citing articles on Scopus
    View full text