Zeolitic imidazolate frameworks (ZIFs) based electrocatalysts for CO₂ reduction offer unique possibilities for developing advanced materials for this reaction due to their ordered nanoporosity and pore environments, tunable characteristics and high affinity for CO₂. Still, they were not investigated sufficiently. In this study, we developed a Bismuth nanodots embedded Zeolitic Imidazolate Framework-8 (BND-ZIF-8) electrocatalyst via a one-pot synthesis method for the electrochemical CO₂ reduction reaction (eCO₂RR). Comprehensive spectroscopic and electrochemical characterization confirmed the successful integration of Bismuth into the ZIF-8 matrix. The electrocatalytic performance of the BND-ZIF-8 was assessed in multiple reactor typologies such as H-cell, flow cell, and membrane electrode assembly (MEA) setups. Remarkable differences in the performances in the three cell configurations are evidenced. Notably, the MEA configuration exhibited a marked enhancement in formate selectivity, achieving a Faradic efficiency (FE) of up to 91 % at a current density of −150 mA cm^‒². This work underscores the potential of Bi-ZIF-8 in advancing eCO₂RR while remarking on the crucial importance of the appropriate type of electrocatalytic experiments in assessing the material performance.

Copper and copper-based catalysts can electrochemically convert CO₂ into ethylene and higher alcohols, among other products, at room temperature and pressure. This approach may be suitable for the production of high-value compounds. However, such a promising reaction is heavily burdened by the instability of copper during CO₂ reduction. To date, non-copper catalysts have also failed to supplant the activity and selectivity of copper, leaving CO₂-to-C₂ electrolysis in the balance. In this Perspective, we discuss copper catalyst instability from both the atomistic and the microstructure viewpoint. We motivate that increased fundamental understanding, material design and operational approaches, along with increased reporting of failure mechanisms, will contribute to overcoming the barriers to multi-year operation. Our narrative focuses on the copper catalyst reconstruction occurring during CO₂ reduction as one of the major causes inducing loss of C₂ activity. We conclude with a rational path forward towards longer operations of CO₂-to-C₂ electrolysis.

In Fig. 4(e) on page 6733 of this article, the legends in the graph for faradaic efficiency of CO and C2+ were misplaced. The original figure should be replaced with an updated one. Note that this correction does not have any impact on the main idea and conclusion of this article. The updated Fig. 4 is as follows. The Royal Society of Chemistry apologises for these errors and any consequent inconvenience to authors and readers. (Figure presented).

Electrochemical ammonia (NH₃) synthesis from nitrate (NO₃⁻) offers a promising greener alternative to the fossil-fuel-based Haber-Bosch process to support the increasing demand for nitrogen fertilizers while removing environmental waste. Previous studies have mainly focused on designing catalysts to promote the direct conversion (NO₃⁻ → NH₃) while suppressing the two-step pathway (NO₃⁻ → NO₂⁻ → NH₃). We hypothesize that efficient nitrate reduction is possible on simple catalysts by instead promoting the two-step reaction and using chemical reactor principles in a membrane electrode assembly, despite NO₂⁻ intermediates. Here, we use an unmodified copper catalyst and control reactivity through current density, flow rate, and electrolyte recycling. Balancing the electrolyte flow rate with current density results in ideal residence times for NO₂⁻, allowing for 91% FE_NH3 in a 5 cm² electrolyzer with a NO₃⁻ to NH₃ partial current of 1.8 A. This work shows that traditional engineering principles can substantially boost the NO₃ reduction reaction, even for simple catalysts.

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.

Using copper (Cu) as an electrocatalyst uniquely produces multicarbon products (C₂₊-products) during the CO₂ reduction reaction (CO2RR). However, the CO2RR stability of Cu is presently 3 orders of magnitude shorter than required for commercial operation. One means of substantially increasing Cu catalyst lifetimes is through periodic oxidative processes, such as cathodic-anodic pulsing. Despite 100-fold improvements, these oxidative methods only delay, but do not circumvent, degradation. Here, we provide an interrogation of chemical and electrochemical Cu oxidative processes to identify the mechanistic processes leading to stable CO2RR through electrochemical and in situ Raman spectroscopy measurements. We first examine chemical oxidation using an open-circuit potential (OCP), identifying that copper oxidation is regulated by the transient behavior of the OCP curve and limited by the rate of the oxygen reduction reaction (ORR). Increasing O₂ flux to the cathode subsequently increased ORR rates, both extending lifetimes and reducing “off” times by 3-fold. In a separate approach, the formation of Cu₂O is achieved through electrochemical oxidation. Here, we establish the minimum electrode potentials required for fast Cu oxidation (−0.28 V vs Ag/AgCl, 1 M KHCO₃) by accounting for transient local pH changes and tracking oxidation charge transfer. Lastly, we performed a stability test resulting in a 20-fold increase in stable ethylene production versus the continuous case, finding that spatial copper migration is slowed but not mitigated by oxidative pulsing approaches alone.