Electrochemical ammonia synthesis via the nitrogen reduction reaction (NRR) has been poised as one of the promising technologies for the sustainable production of green ammonia. In this work, we developed extensive process models of fully integrated electrochemical NH ₃ production plants at small scale (91 tonnes per day), including their techno-economic assessments, for (Li-)mediated, direct and indirect NRR pathways at ambient and elevated temperatures, which were compared with electrified and steam-methane reforming (SMR) Haber-Bosch processes. The levelized cost of ammonia (LCOA) of aqueous NRR at ambient conditions only becomes comparable with SMR Haber-Bosch at very optimistic electrolyzer performance parameters (FE > 80% at j ≥ 0.3 A cm ⁻²) and electricity prices (<$0.024 per kW h). Both high temperature NRR and Li-mediated NRR are not economically comparable within the tested variable ranges. High temperature NRR is very capital intensive due the requirement of a heat exchanger network, more auxiliary equipment and an additional water electrolyzer (considering the indirect route). For Li-mediated NRR, the high lithium plating potentials, ohmic losses and the requirement for H ₂, limits its commercial competitiveness with SMR Haber-Bosch. This incentivises the search for materials beyond lithium.

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Carbon dioxide (CO2) electrolysis on copper (Cu) catalysts has attracted interest due to its direct production of C2+ feedstocks. Using the knowledge that CO2 reduction on copper is primarily a tandem reaction of CO2 to CO and CO to C2+ products, we show that modulating CO concentrations within the liquid catalyst layer allows for a C2+ selectivity of >80% at 200 mA cm−2 under broad conversion conditions. The importance of CO pooling is demonstrated through residence time distribution curves, varying flow fields (serpentine/parallel/interdigitated), and flow rates. While serpentine flow fields require high conversions to limit CO selectivity and maximize C2+ selectivity, the longer CO residence times of parallel flow fields achieve similar selectivity over broad flow rates. Critically, we show that parts of the catalyst area predominantly reduce CO instead of CO2 as supported by CO reduction experiments, transport modelling, and achieving a CO2 utilization efficiency greater than the theoretical limit of 25% for C2+ products.@en

Aqueous electrolytes used in CO2 electroreduction typically have a CO2 solubility of around 34 mM under ambient conditions, contributing to mass transfer limitations in the system. Non-aqueous electrolytes exhibit higher CO2 solubility (by 5–8-fold) and also provide possibilities to suppress the undesired hydrogen evolution reaction (HER). On the other hand, a proton donor is needed to produce many of the products commonly obtained with aqueous electrolytes. This work investigates the electrochemical CO2 reduction performance of copper in non-aqueous electrolytes based on dimethylformamide (DMF), n-methyl-2-pyrrolidone (NMP), and acetonitrile (ACN). The main objective is to analyze whether non-aqueous electrolytes are a viable alternative to aqueous electrolytes for hydrocarbon production. Additionally, the effects of aqueous/non-aqueous anolytes, membrane, and the selection of a potential window on the electrochemical CO2 reduction performance are addressed in this study. Experiments with pure DMF and NMP mainly produced oxalate with a faradaic efficiency (FE) reaching >80%; however, pure ACN mainly produced hydrogen and formate due to the presence of more residual water in the system. Addition of 5% (v/v) water to the non-aqueous electrolytes resulted in increased HER and formate production with negligible hydrocarbon production. Hence, we conclude that aqueous electrolytes remain a better choice for the production of hydrocarbons and alcohols on a copper electrode, while organic electrolytes based on DMF and NMP can be used to obtain a high selectivity toward oxalate and formate.@en

Electrochemical carbon dioxide reduction to multi-carbon products such as ethylene and ethanol is a promising method to store electricity in chemical bonds and produce bulk chemicals from CO2. Simultaneous consideration of processes taking place at the molecular scale, electrolyser scale, and the process scale is crucial to efficiently move towards commercialization and avoid optimizing for unrealistic operating conditions. This chapter summarizes the relevant considerations at each vantage point and reviews the latest developments in CO2 reduction toward multi-carbon products at different scales.@en