Abstract
Electrocatalytic nitrate (NO
3
−
) reduction to ammonia (NRA) has emerged as an alternative strategy for effluent treatment and ammonia production. Despite significant advancements that have ...been achieved in this field, the efficient conversion of low-concentration nitrate to ammonia at low overpotential remains a formidable challenge. This challenge stems from the sluggish reaction kinetics caused by the limited distribution of negatively charged NO
3
−
in the vicinity of the working electrode and the competing side reactions. Here, a pulsed potential approach is introduced to overcome these issues. A good NRA performance (Faradaic efficiency: 97.6%, yield rate: 2.7 mmol
−1
h
−1
mg
Ru
−1
, conversion rate: 96.4%) is achieved for low-concentration (≤10 mM) nitrate reduction, obviously exceeding the potentiostatic test (Faradaic efficiency: 65.8%, yield rate: 1.1 mmol
−1
h
−1
mg
Ru
−1
, conversion rate: 54.1%). The combined results of in situ characterizations and finite element analysis unveil the performance enhancement mechanism that the periodic appearance of anodic potential can significantly optimize the adsorption configuration of the key *NO intermediate and increase the local NO
3
−
concentration. Furthermore, our research implies an effective approach for the rational design and precise manipulation of reaction processes, potentially extending its applicability to a broader range of catalytic applications.
Abstract
Electrochemical conversion of abundant carbon- and nitrogen-containing small molecules into high-valued organonitrogen compounds is alluring to reducing current dependence on fossil energy. ...Here we report a single-cell electrochemical oxidation approach to transform methanol and ammonia into formamide under ambient conditions over Pt electrocatalyst that provides 74.26% selectivity from methanol to formamide and a Faradaic efficiency of 40.39% at 100 mA cm
−2
current density, gaining an economic advantage over conventional manufacturing based on techno-economic analysis. A 46-h continuous test performed in the flow cell shows no performance decay. The combined results of in situ experiments and theoretical simulations unveil the C–N bond formation mechanism via nucleophilic attack of NH
3
on an aldehyde-like intermediate derived from methanol electrooxidation. This work offers a way to synthesize formamide via C–N coupling and can be extended to substantially synthesize other value-added organonitrogen chemicals (e.g., acetamide, propenamide, formyl methylamine).
The traditional synthesis of syngas, a mixture of CO and H2, relies on the reverse water gas shift reaction at high temperature and thus consumes considerable energy and resources. In this regard, ...the electrochemical conversion of CO2-H2O to CO-H2 provides an emerging alternative technique to conquer these shortages. This short review highlights the recent advances and future trends in the electrocatalytic transformation of CO2 and H2O to syngas with a tunable H2:CO ratio. We summarize the latest advances in metals, metal oxides and chalcogenides, metal complex catalysts, single-atom catalysts, and metal-free catalysts with an emphasis on controlling the CO:H2 ratio, which is vital for downstream Fischer-Tropsch process synthesis. Then we introduce versatile methods to improve the production efficiency of syngas by alternative anode reactions and advanced technologies (e.g., gas diffusion electrode-based, flow, solid oxide electrolytic cells). Finally, we provide an outlook on the current challenges and promising opportunities in the field of syngas synthesis.
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The traditional synthesis of syngas relies on the reverse water gas shift reaction at high temperatures and thus consumes considerable energy and resources. As such, the electrochemical conversion of CO2-H2O to CO-H2 is an attractive alternative technique. This short review highlights the recent advances and future trends in the electrocatalytic transformation of CO2 and H2O to syngas with a tunable H2:CO ratio.
As a sustainable alternative to fossil fuel-based manufacture of bulk oxygenates, electrochemical synthesis using CO and H
O as raw materials at ambient conditions offers immense appeal. However, the ...upscaling of the electrosynthesis of oxygenates encounters kinetic bottlenecks arising from the competing hydrogen evolution reaction with the selective production of ethylene. Herein, a catalytic relay system that can perform in tandem CO capture, activation, intermediate transfer and enrichment on a Cu-Ag composite catalyst is used for attaining high yield CO-to-oxygenates electrosynthesis at high current densities. The composite catalyst Cu/30Ag (molar ratio of Cu to Ag is 7:3) enables high efficiency CO-to-oxygenates conversion, attaining a maximum partial current density for oxygenates of 800 mA cm
at an applied current density of 1200 mA cm
, and with 67 % selectivity. The ability to finely control the production of ethylene and oxygenates highlights the principle of efficient catalyst design based on the relay mechanism.
Efficient electrochemical reduction of CO2 and H2O into industrial syngas with tunable CO/H2 ratios, especially integrated with anodic organic synthesis to replace the low‐value oxygen evolution ...reaction (OER), is highly desirable. Here, integration of controllable partial substitution of zinc (Zn) with amine incorporation into CdS‐amine inorganic‐organic hybrids is used to generate highly efficient electrocatalysts for synthesizing syngas with tunable CO/H2 ratios (0–19.7), which are important feedstocks for the Fischer–Tropsch process. Diethylenetriamine could enhance the adsorption and accelerate the activation of CO2 to form the key intermediate COOH* for CO formation. Zn substitution promoted the hydrogen evolution reaction (HER), leading to tunable CO/H2 ratios. Importantly, syngas and dihydroisoquinoline can be simultaneously synthesized by pairing with anodic semi‐oxidation of tetrahydroisoquinoline in a ZnxCd1−xS‐Amine ∥ Ni2P two‐electrode electrolyzer.
Controlled partial substitution of Zn and amine incorporation into ZnxCd1−xS‐Amine inorganic–organic hybrids resulted in highly efficient electrocatalysts for synthesizing syngas with tunable CO/H2 ratios (0–19.7). Syngas and dihydroisoquinoline can be simultaneously produced at a low cell voltage.
Electrochemical reduction of carbon dioxide (CO2) to fuels and value-added chemicals provides an intriguing approach to realizing the artificial carbon cycle. The development of low-cost ...electrocatalysts with high activity, selectivity, and stability for CO2 reduction is of great significance but still a big challenge. Herein, we present a dual-functionalization strategy to synergistically active polymeric carbon nitride (PCN) for CO2 electroreduction by modifying hydroxyl and amino groups on the surface. Compared with unmodified PCN, a 17.1-fold enhancement for CO yield rate is achieved. The optimized ratio of CO/H2 is 0.67, which is in the range for Fischer–Tropsch reactions (0.25–3.34). The experiments and theory calculations propose that the superficial hydroxyl and amino groups both serve as active sites for synergetic activation of CO2. This work may open an avenue for designing other metal-free electrocatalysts for CO2 conversion.
Urea electrosynthesis under mild conditions shows great potential to conquer the conventional manufacturing industry with huge energy consumption. Here, self-supported oxygen vacancy-rich ZnO (ZnO-V) ...porous nanosheets are prepared using the electroreduction method and adopted as an efficient catalyst for aqueous urea electrosynthesis by using CO2 and nitrite contaminants as feedstocks. The urea Faradaic efficiency of ZnO-V achieves 23.26% at −0.79 V versus the reversible hydrogen electrode (RHE), which is almost 3 times as high as that of ZnO (8.10%). Liquid chromatography is developed for quantitative analysis of urea. The combined results of online differential electrochemical mass spectrometry (DEMS) and in situ attenuated total internal reflectance Fourier Transform infrared spectroscopy unveil a possible coupling pathway of NH2∗ and COOH∗ intermediates for urea formation. Our work opens an avenue for rational construction of efficient electrocatalysts for urea electrosynthesis and broadens the scope of products available from nitrite and CO2 reduction.
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ZnO-V is prepared using the electroreduction methodZnO-V delivers efficient urea electrosynthesis using CO2 and nitrite as feedstocksA coupling pathway of NH2∗ and COOH∗ intermediates for urea formation is unveiled
Using CO2 and inorganic feedstocks to construct the C-N bond is significant for CO2 conversion and synthetic chemistry. Meng et al. demonstrate that self-supported oxygen vacancy-rich ZnO porous nanosheets can be adopted as efficient catalysts for urea electrosynthesis by co-feeding CO2 and nitrite ions.
Urea electrosynthesis provides an intriguing strategy to improve upon the conventional urea manufacturing technique, which is associated with high energy requirements and environmental pollution. ...However, the electrochemical coupling of NO3 – and CO2 in H2O to prepare urea under ambient conditions is still a major challenge. Herein, self-supported core–shell Cu@Zn nanowires are constructed through an electroreduction method and exhibit superior performance toward urea electrosynthesis via CO2 and NO3 – contaminants as feedstocks. Both 1H NMR spectra and liquid chromatography identify urea production. The optimized urea yield rate and Faradaic efficiency over Cu@Zn can reach 7.29 μmol cm–2 h–1 and 9.28% at −1.02 V vs RHE, respectively. The reaction pathway is revealed based on the intermediates detected through in situ attenuated total reflection Fourier transform infrared spectroscopy and online differential electrochemical mass spectrometry. The combined results of theoretical calculations and experiments prove that the electron transfer from the Zn shell to the Cu core can not only facilitate the formation of *CO and *NH2 intermediates but also promote the coupling of these intermediates to form C–N bonds, leading to a high faradaic efficiency and yield of the urea product.
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