Electrochemical reduction of CO2 to multi-carbon products is very attractive yet particularly challenging due to the low efficiency of C-C coupling over currently used electrocatalysts. In this work, ...we report a dual-atom catalyst (Cu2/NC) capable of selectively promoting electro-reduction of CO2 to C2H4. The Faradaic efficiency of CO2-to-C2H4 over the Cu2/NC is up to ∼34.9% with a current density of 33.6 mA·cm−2. By contrast, its Cu single-atom counterpart only generates CO without forming C2H4. The density functional theory (DFT) calculations reveal that the Cu-Cu sites largely promote the adsorption of *CO and reduce the energy barrier of C-C coupling between the adsorbed *CO relative to that of the single Cu sites, which accounts for the high C2H4 selectivity of the Cu2/NC.
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•Highly efficient Cu dual-atom catalysts were prepared to catalyze CO2RR.•Compared with Cu single-atom catalyst, dual-atom catalyst was more favorable to reduce CO2 to multi-carbon product C2H4.•DFT calculations revealed that the energy barrier of C-C coupling was largely reduced on the dual Cu catalysts.
MXene-based catalysts have shown excellent activities in various electrocatalytic reactions due to the two-dimensional structure, good electrical conductivity and abundant surface functional groups. ...However, because of the competitive reactions in aqueous electrolytes, the application of MXene materials in CO2 electroreduction still remains a challenge. Herein, a simple strategy was developed for the design of high efficient and stable CO2 electroreduction catalysts in aqueous electrolyte. A series of MXene composite catalysts were successfully synthesized by densely coating sulfur vacancy-rich CdS nanoparticles on Ti3C2. The two-dimensional MXene skeleton with good conductivity delivers fast electron transfer, improves the electrolyte infiltration and increases the electrochemical surface area. CdS nanoparticles with abundant sulfur vacancies are attached on Ti3C2 MXene surface, providing active sites for CO2 reduction. Faraday efficiency of the by-product hydrogen could be significantly reduced by minimizing the surface-exposed Ti of the catalyst. Benefited from these merits, the optimal CdS/Ti3C2 possesses fast CO2 electroreduction reaction kinetics, exhibiting a high CO Faraday efficiency of 94% at -1.0 V vs. reversible hydrogen electrode. This work provides a feasible pathway for the design of MXene-based catalysts of CO2 electroreduction.
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•MXene-based catalysts are applied in aqueous electrolyte system CO2ERR.•The H2 Faradaic efficiency can be controlled by adjusting the surface-exposed Ti.•The sulfur vacancy improves CO2ERR property of CdS/Ti3C2 nanocomposite.•CO Faraday efficiency of the electrocatalyst reaches up to 94% at -1.0 V vs. RHE.
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•Heteronuclear Pr1-Ni1 active sites with Pr-N4C2 and Ni-N4 moieties were constructed.•Pr/Ni-NC shows 99.1 % FECO with commercial-scale current density of 237 mA cm−2.•Pr site ...facilitates CO2 activation and Ni site enables H2O dissociation for CO2RR.
Lanthanide metals have attracted particular interest in the catalysis of electrochemical CO2 reduction. The synthesis and precise spatial distribution of active sites are fundamental important but still formidably challenging owing to the strong oxygen affinity of lanthanide. Here, heteronuclear Pr1-Ni1 single atoms are supported on the carbon matrix containing surface framework defects from lanthanide contraction. The Pr/Ni-NC catalyst exhibits a CO Faradaic efficiency of 99.1 % with a commercial-scale current density of 237 mA cm−2 and a turnover frequency as high as 18,038 h−1 at −1.1 V due to d-f coupling effect and electronic structure perturbation of Pr. Furthermore, mechanistic investigations unveil that the diatomic active sites effectively reduce the energy barrier of the crucial *COOH formation, in which the Pr site facilitates CO2 activation and the Ni site enables H2O dissociation to accelerate the proton transfer process, thereby ensuring the synergy of catalytic sites to greatly facilitate CO2-to-CO conversion.
As a favorite descriptor, the size effect of Cu‐based catalysts has been regularly utilized for activity and selectivity regulation toward CO2/CO electroreduction reactions (CO2/CORR). However, ...little progress has been made in regulating the size of Cu nanoclusters at the atomic level. Herein, the size‐gradient Cu catalysts from single atoms (SAs) to subnanometric clusters (SCs, 0.5–1 nm) to nanoclusters (NCs, 1–1.5 nm) on graphdiyne matrix are readily prepared via an acetylenic‐bond‐directed site‐trapping approach. Electrocatalytic measurements show a significant size effect in both the activity and selectivity toward CO2/CORR. Increasing the size of Cu nanoclusters will improve catalytic activity and selectivity toward C2+ productions in CORR. A high C2+ conversion rate of 312 mA cm−2 with the Faradaic efficiency of 91.2 % are achieved at −1.0 V versus reversible hydrogen electrode (RHE) over Cu NCs. The activity/selectivity‐size relations provide a clear understanding of mechanisms in the CO2/CORR at the atomic level.
The size‐controlled Cu catalysts from single atoms to subnanometric clusters (0.5–1 nm) to nanoclusters (1–1.5 nm) on a graphdiyne matrix are prepared by an acetylenic‐bond‐directed site‐trapping approach. Size dependence of activity and selectivity in the CO/CO2 reduction reaction (CO/CO2RR) over these catalysts is shown for the first time.
Electrochemical reduction of carbon dioxide to hydrocarbons, driven by renewable power sources, is a fascinating and clean way to remedy greenhouse gas emission as a result of overdependence on ...fossil fuels and produce value-added fine chemicals. The Cu-based catalysts feature unique superiorities; nevertheless, achieving high hydrocarbon selectivity is still inhibited and remains a great challenge. In this study, we report on a tailor-made multifunction-coupled Cu-metal-organic framework (Cu-MOF) electrocatalyst by time-resolved controllable restructuration from Cu
O to Cu
O@Cu-MOF. The restructured electrocatalyst features a time-responsive behavior and is equipped with high specific surface area for strong adsorption capacity of CO
and abundant active sites for high electrocatalysis activity based on the as-produced MOF on the surface of Cu
O, as well as the accelerated charge transfer derived from the Cu
O core in comparison with the Cu-MOF. These intriguing characteristics finally lead to a prominent performance towards hydrocarbons, with a high hydrocarbon Faradaic efficiency (FE) of 79.4%, particularly, the CH
FE as high as 63.2% (at -1.71 V). This work presents a novel and efficient strategy to configure MOF-based materials in energy and catalysis fields, with a focus on big surface area, high adsorption ability, and much more exposed active sites.
Amorphous oxides have attracted special attention as advanced electrocatalysts owing to their unique local structural flexibility and attractive electrocatalytic properties. With abundant randomly ...oriented bonds and surface‐exposed defects (e.g., oxygen vacancies) as active catalytic sites, the adsorption/desorption of reactants can be optimized, leading to superior catalytic activities. Amorphous oxide materials have found wide electrocatalytic applications ranging from hydrogen evolution and oxygen evolution to oxygen reduction, CO2 electroreduction and nitrogen electroreduction. The amorphous oxide electrocatalysts even outperform their crystalline counterparts in terms of electrocatalytic activity and stability. Despite of the merits and achievements for amorphous oxide electrocatalysts, there are still issues and challenges existing for amorphous oxide electrocatalysts. There are rarely reviews specifically focusing on amorphous oxide electrocatalysts and therefore it is imperative to have a comprehensive overview of the research progress and to better understand the achievements and issues with amorphous oxide electrocatalysts. In this minireview, several general preparation methods for amorphous oxides are first introduced. Then, the achievements in amorphous oxides for several important electrocatalytic reactions are summarized. Finally, the challenges and perspectives for the development of amorphous oxide electrocatalysts are outlined.
Amorphous vs. crystalline: With unique structural and electronic properties, such as disordered ordering, more dangling bonds, and oxygen vacancies, and abundant surface defects, amorphous oxides have found wide electrocatalytic applications ranging from the hydrogen and oxygen evolution reactions, the oxygen reduction reaction, to the CO2 and nitrogen reduction reactions. In this minireview, the preparation methods, research progress, and perspectives for amorphous oxide nanostructures are demonstrated.
Table of contents for mechanism model of Cu-N3 and Cu-N4 moieties.
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•Highly exposed isolated Cu-Nx sites were embedded in microporous carbon frameworks.•CO2-to-CO conversion was ...boosted with tailored Cu–N coordination environment.•Cu-N4 exhibited a maximum FECO of 98% and over 90% from −0.6 to −1.1 V vs. RHE.•Edge-hosted Cu-N4 was identified as the accurate configuration of active site by DFT calculations.
Although considerable progress has been achieved by Cu nanoparticles for catalyzing CO2 reduction reaction (CO2RR), Cu single atom catalysts (Cu SACs) are generally suffered from inferior performance to that of widely investigated Fe, Co, Ni SACs. This phenomenon mainly ascribes to the lack of effective geometry and electronic engineering of copper active center from an atomic level. Herein, highly exposed atomically dispersed Cu-Nx (x denotes Cu–N coordination number) sites anchored on 3D porous carbon matrix are successfully synthesized through facile one step thermal activation, and Cu-N4 sites exhibit boosted activity and selectivity compared to its nearly inert Cu-N3 counterparts. Aided by density functional theory (DFT) calculations, the edge-hosted Cu-N4 moieties are revealed as key active sites for efficient CO generation via optimized local coordination environment and electronic properties, which strongly interact with *COOH intermediate and facilitate the desorption of *CO. As a result, Cu-N4 catalyst achieves high CO Faradaic efficiency (FECO) of over 90% from −0.6 to −1.1 V vs. RHE with a maximum value of 98%, surpassing the previously reported Cu SACs for CO2-to-CO conversion. This work provides new insight into proper Cu SACs design and fundamental mechanism understanding to boost CO2RR.
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•S/N co-coordinated Ni single-atom (Ni-SNC) was proposed to promote CO2RR.•Unsaturated coordination of Ni-N3 reduced the energy barrier of key steps.•Sulfur doping regulated ...electronic density of unsaturated Ni-N3.•Ni-SNC electrocatalyst exhibited a peak FECO of 95% at −0.8 V vs RHE.
Tuning coordination environment of metal atoms in catalysts can improve intrinsic performance of CO2 reduction and accelerate kinetics of CO formation. However, constructing unsaturated coordination configuration of metal single-atom by heteroatom doping still remains a challenge. Herein, a novel electrocatalyst of S/N co-coordinated Ni single-atom (denoted as Ni-SNC) was synthesized by calcining SO42- doped Zn/Ni ZIF for electrocatalytic CO2 reduction. The existence of single-atom Ni was verified by HAADF-STEM, while formation of “unsaturated” Ni-N3-S active sites was confirmed by XANES and EXAFS. The energy barrier of pivotal steps in CO2RR reaction process was reduced on “unsaturated” Ni-N3-S active sites, and sulfur doping improved current density of electrocatalytic process. The energy barrier of CO2→COOH* over Ni-SNC catalyst was only +0.69 eV, which was much less than that (+2.02 eV) over Ni-NC catalyst. The Ni-SNC exhibited CO Faradaic efficiency (FECO) of >90% at -0.6 ∼ -0.9 V vs. RHE with the highest FECO of 95% at −0.8 V.
Abstract
Tuning surface electron transfer process by oxygen (O)‐vacancy engineering is an efficient strategy to develop enhanced catalysts for CO
2
electroreduction (CO
2
ER). Herein, a series of ...distinct InO
x
NRs with different numbers of O‐vacancies, namely, pristine (P‐InO
x
), low vacancy (O‐InO
x
) and high‐vacancy (H‐InO
x
) NRs, have been prepared by simple thermal treatments. The H‐InO
x
NRs show enhanced performance with a best formic acid (HCOOH) selectivity of up to 91.7 % as well as high HCOOH partial current density over a wide range of potentials, largely outperforming those of the P‐InO
x
and O‐InO
x
NRs. The H‐InO
x
NRs are more durable and have a limited activity decay after continuous operating for more than 20 h. The improved performance is attributable to the abundant O‐vacancies in the amorphous H‐InO
x
NRs, which optimizes CO
2
adsorption/activation and facilitates electron transfer for efficient CO
2
ER.
Electroreduction of N2 into NH3 represents a promising method for N2 fixation. However, due to the inertness of NN covalent triple bonds, this process remains a huge challenge to achieve a high ...yield rate of NH3. In this work, we designed an effective approach to promoting N2 activation by introducing oxygen vacancies into LaCoO3. In N2 electroreduction, LaCoO3 with oxygen vacancies (denoted as V o-LaCoO3) exhibited a Faradaic efficiency of 7.6% for NH3 at −0.6 V versus the reversible hydrogen electrode (RHE). Notably, at −0.7 V versus RHE, the yield rate for NH3 of V o-LaCoO3 reached 182.2 μgNH3 mg–1 cat. h–1, which was 2.8 times higher than that (65.3 μgNH3 mg–1 h–1) of pristine LaCoO3. To the best of our knowledge, the yield rate for NH3 of V o-LaCoO3 approaches the activities of the state-of-the-art catalysts toward N2 electroreduction. Density functional theory calculations revealed that enhanced activation of N2 over V o-LaCoO3 originated from the increased charge density around the valence band edge via the introduction of oxygen vacancies. Furthermore, the analysis of the thermodynamic limiting potentials for N2 reduction and H2 evolution demonstrated the higher selectivity for N2 electroreduction over V o-LaCoO3 relative to pristine LaCoO3.
