Multiple Tuning of the Local Environment Enables Selective CO2 Electroreduction to Ethylene in Neutral Electrolytes

Recently, vigorous progress is made in the selective and high-current reduction of carbon dioxide (CO₂) to ethylene (C₂H₄) by using a flow cell. In most cases, however, the reduction is only achieved in strong alkaline electrolytes, which results in substantial deactivation of electrocatalysts due to the accumulation of precipitates. Here, porous Cu nanowires (NWs) is prepared with abundant atomic defects, which create a synergy with the pore-induced electric field to comprehensively tune the local microenvironment of the electrode surface, thus enabling efficient and stable C₂H₄ production from the CO₂ reduction reaction (CO₂RR) in neutral media. In particular, the enhanced electric field effect increases the local K⁺ concentration for the generation of *CO intermediates; while the atomic defects stabilize OH⁻ and *CO, leading to high local pH and *CO coverage. Such synergy can provide a favorable local environment and high *CO coverage for significantly decreasing the energy barrier of the C─C coupling step. Consequently, a large partial C₂H₄ current density of 222.3 mA cm⁻² with excellent stability is achieved in a neutral electrolyte. Altogether, this work paves new pathways to promote C₂H₄ production in the neutral CO₂RR through multiple tuning of the local environment.     

Boosting Industrial-Level CO2 Electroreduction of N-Doped Carbon Nanofibers with Confined Tin-Nitrogen Active Sites via Accelerating Proton Transport Kinetics

The development of highly efficient robust electrocatalysts with low overpotential and industrial-level current density is of great significance for CO₂ electroreduction (CO₂ER), however the low proton transport rate during the CO₂ER remains a challenge. Herein, a porous N-doped carbon nanofiber confined with tin-nitrogen sites (Sn/NCNFs) catalyst is developed, which is prepared through an integrated electrospinning and pyrolysis strategy. The optimized Sn/NCNFs catalyst exhibits an outstanding CO₂ER activity with the maximum CO FE of 96.5%, low onset potential of −0.3 V, and small Tafel slope of 68.8 mV dec⁻¹. In a flow cell, an industrial-level CO partial current density of 100.6 mA cm⁻² is achieved. In situ spectroscopic analysis unveil the isolated Sn N site acted as active center for accelerating water dissociation and subsequent proton transport process, thus promoting the formation of intermediate *COOH in the rate-determining step for CO₂ER. Theoretical calculations validate pyrrolic N atom adjacent to the Sn N active species assisted reducing the energy barrier for *COOH formation, thus boosting the CO₂ER kinetics. A Zn-CO₂ battery is designed with the cathode of Sn/NCNFs, which delivers a maximum power density of 1.38 mW cm⁻² and long-term stability.     

Tandem Catalysis for Enhanced CO2 to Ethylene Conversion in Neutral Media

Selective electrochemical CO₂ reduction reaction (CO₂RR) into value-added hydrocarbon products such as C₂H₄ provides a sustainable approach to producing carbon chemicals, which however remains a great challenge owing to the multi-electron transfer process during CO₂ electroreduction. Herein, a tandem catalyst a-Ni/Cu-NP@CMK is developed by encapsulating Cu nanoparticles (Cu NPs) into hydrophobic cubic mesoporous carbon with doped atomic Ni-N₄ moieties. Electrochemical tests demonstrate the outstanding C₂H₄ selectivity of a-Ni/Cu-NP@CMK with a high Faraday efficiency (FE) of 72.3% for C₂H₄ at a large current density of 406.1 mA cm⁻² in a flow cell under a neutral medium. Moreover, when used as the cathode catalyst in membrane electrode assembly, a-Ni/Cu-NP@CMK stably delivers a current density of 200 mA cm⁻² with a FE_C2H4 of 63% at -2.8 V for 30 h, providing a full-cell energy efficiency of 28.3% for C₂H₄ production. Comparative studies disclose that the hydrophobic microenvironment of the Cu NPs in a-Ni/Cu-NP@CMK successfully suppresses the competitive hydrogen evolution reaction and improves the CO₂RR selectivity. Additionally, in situ spectroscopic investigations and theoretical calculations reveal that the efficient CO₂-to-CO conversion on the Ni-N₄ moieties feeds Cu NPs with enriched adsorbed CO (*CO), which facilitates the C─C coupling between adjacent *CO to form C₂H₄.