Linking the Dynamic Chemical State of Catalysts with the Product Profile of Electrocatalytic CO<sub>2</sub> Reduction

Wang, Jiali; Tan, Hui‐Ying; Zhu, Yanping; Chu, Hang; Chen, Hao Ming

doi:10.1002/ange.202017181

Cited by 61 publications

(22 citation statements)

References 84 publications

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“…Energy-efficient NO 3 RR points to low operating overpotentials (e.g., >−0.2 V vs. RHE), at which transition metal (e.g., Cu and Co)-based catalysts often suffer from potential−dependent phase evolution, leading to the coexistence of multiple phases, such as metallic, oxide and hydroxide phases 53 – 56 . In situ monitoring of the phase evolution of transition metals during the NO 3 RR, while correlating these intermediate phases with specific catalytic steps 53 , 54 , 57 , 58 , may not only guide the rational design of selective catalysts for NH 3 but also provide insight into the NO 3 RR. Inspired by the tandem NO 3 − -to-NH 3 conversion in nature 29 , we sought, therefore, to circumvent the scaling relations by combining two or more cooperative intermediate phases exhibiting complementary catalytic selectivity into one tandem system, intending to achieve NH 3 synthesis at low overpotentials.…”

Section: Introductionmentioning

confidence: 99%

Splicing the active phases of copper/cobalt-based catalysts achieves high-rate tandem electroreduction of nitrate to ammonia

et al. 2022

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Electrocatalytic recycling of waste nitrate (NO3−) to valuable ammonia (NH3) at ambient conditions is a green and appealing alternative to the Haber−Bosch process. However, the reaction requires multi-step electron and proton transfer, making it a grand challenge to drive high-rate NH3 synthesis in an energy-efficient way. Herein, we present a design concept of tandem catalysts, which involves coupling intermediate phases of different transition metals, existing at low applied overpotentials, as cooperative active sites that enable cascade NO3−-to-NH3 conversion, in turn avoiding the generally encountered scaling relations. We implement the concept by electrochemical transformation of Cu−Co binary sulfides into potential-dependent core−shell Cu/CuOx and Co/CoO phases. Electrochemical evaluation, kinetic studies, and in−situ Raman spectra reveal that the inner Cu/CuOx phases preferentially catalyze NO3− reduction to NO2−, which is rapidly reduced to NH3 at the nearby Co/CoO shell. This unique tandem catalyst system leads to a NO3−-to-NH3 Faradaic efficiency of 93.3 ± 2.1% in a wide range of NO3− concentrations at pH 13, a high NH3 yield rate of 1.17 mmol cm−2 h−1 in 0.1 M NO3− at −0.175 V vs. RHE, and a half-cell energy efficiency of ~36%, surpassing most previous reports.

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Section: Introductionmentioning

confidence: 99%

Splicing the active phases of copper/cobalt-based catalysts achieves high-rate tandem electroreduction of nitrate to ammonia

et al. 2022

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“…Yu et al found that in situ generated CO 2 RR intermediates on the surface of OD-Cu stabilize Cu δ+ species 8 . Chen et al pointed out that the chemical states of Cu are associated with the oxidation caused by an uncertain oxidative species in the electrolytes 25 – 27 . We took the view that the Cu δ+ species should be dynamically existing, and we propose that the redox conditions provided by electrochemical cathodic reduction and oxidative species in electrolytes should be crucial.…”

Section: Introductionmentioning

confidence: 99%

Hydroxyl radicals dominate reoxidation of oxide-derived Cu in electrochemical CO2 reduction

et al. 2022

Nat Commun

133

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Cuδ+ sites on the surface of oxide-derived copper (OD-Cu) are of vital importance in electrochemical CO2 reduction reaction (CO2RR). However, the underlying reason for the dynamically existing Cuδ+ species, although thermodynamically unstable under reductive CO2RR conditions, remains uncovered. Here, by using electron paramagnetic resonance, we identify the highly oxidative hydroxyl radicals (OH•) formed at room temperature in HCO3- solutions. In combination with in situ Raman spectroscopy, secondary ion mass spectrometry, and isotope-labelling, we demonstrate a dynamic reduction/reoxidation behavior at the surface of OD-Cu and reveal that the fast oxygen exchange between HCO3- and H2O provides oxygen sources for the formation of OH• radicals. In addition, their continuous generations can cause spontaneous oxidation of Cu electrodes and produce surface CuOx species. Significantly, this work suggests that there is a “seesaw-effect” between the cathodic reduction and the OH•-induced reoxidation, determining the chemical state and content of Cuδ+ species in CO2RR. This insight is supposed to thrust an understanding of the crucial role of electrolytes in CO2RR.

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“…Consequently, researchers focus on the development of various catalysts with high activity. [9][10][11] Similarly, substantial efforts have been invested in the fabrication of different CRR catalysts, including single-atom, 12 alloy, 13,14 surface oxidation state, [15][16][17] grain boundaries, 18 solid solutions, 19 morphologies, 20,21 chemical composition, 22 and crystal facet engineering. 23 Nevertheless, differently to thermal catalysis, since CRR occurs on a gas/solid/liquid three-phase interface (Figure 1C), 24 its reactivity is also sensitive to the local reaction environment of the catalysts, such as the specific electrolyte, 25 pH, 26 presence of metal cations, 27 surface structure and composition of the catalyst, 28 and some other factors.…”

Section: Introductionmentioning

confidence: 99%

Customizing the microenvironment of CO₂ electrocatalysis via three‐phase interface engineering

et al. 2022

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Converting CO2 into high‐value fuels and chemicals by renewable‐electricity‐powered electrochemical CO2 reduction reaction (CRR) is a viable approach toward carbon‐emissions‐neutral processes. Unlike the thermocatalytic hydrogenation of CO2 at the solid‐gas interface, the CRR takes place at the three‐phase gas/solid/liquid interface near the electrode surface in aqueous solution, which leads to major challenges including the limited mass diffusion of CO2 reactant, competitive hydrogen evolution reaction, and poor product selectivity. Here we critically examine the various methods of surface and interface engineering of the electrocatalysts to optimize the microenvironment for CRR, which can address the above issues. The effective modification strategies for the gas transport, electrolyte composition, controlling intermediate states, and catalyst engineering are discussed. The key emphasis is made on the diverse atomic‐precision modifications to increase the local CO2 concentration, lower the energy barriers for CO2 activation, decrease the H2O coverage, and stabilize intermediates to effectively control the catalytic activity and selectivity. The perspectives on the challenges and outlook for the future applications of three‐phase interface engineering for CRR and other gas‐involving electrocatalytic reactions conclude the article.

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Linking the Dynamic Chemical State of Catalysts with the Product Profile of Electrocatalytic CO₂ Reduction

Cited by 61 publications

References 84 publications

Splicing the active phases of copper/cobalt-based catalysts achieves high-rate tandem electroreduction of nitrate to ammonia

Splicing the active phases of copper/cobalt-based catalysts achieves high-rate tandem electroreduction of nitrate to ammonia

Hydroxyl radicals dominate reoxidation of oxide-derived Cu in electrochemical CO2 reduction

Customizing the microenvironment of CO₂ electrocatalysis via three‐phase interface engineering

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Linking the Dynamic Chemical State of Catalysts with the Product Profile of Electrocatalytic CO2 Reduction

Cited by 61 publications

References 84 publications

Splicing the active phases of copper/cobalt-based catalysts achieves high-rate tandem electroreduction of nitrate to ammonia

Splicing the active phases of copper/cobalt-based catalysts achieves high-rate tandem electroreduction of nitrate to ammonia

Hydroxyl radicals dominate reoxidation of oxide-derived Cu in electrochemical CO2 reduction

Customizing the microenvironment of CO2 electrocatalysis via three‐phase interface engineering

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Product

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Linking the Dynamic Chemical State of Catalysts with the Product Profile of Electrocatalytic CO₂ Reduction

Customizing the microenvironment of CO₂ electrocatalysis via three‐phase interface engineering