A Multiscale Strategy to Construct Cobalt Nanoparticles Confined within Hierarchical Carbon Nanofibers for Efficient CO2 Electroreduction

Superbase and Hydrophobic Ionic Liquid Confined within Ni Foams as a Free-Standing Catalyst for CO2 Electroreduction

Access to high-performance and cost-effective catalyst materials is one of the crucial preconditions for the industrial application of electrochemical CO₂ reduction (ECR). In this work, a facile and simple strategy is proposed for the construction of a free-standing electrocatalyst via confining a superbase and hydrophobic ionic liquid (IL, [P₆₆₆₁₄][triz]) into Ni foam pores, denoted as [P₆₆₆₁₄][triz]@Ni foam. These ILs can modulate the surface of Ni foam and create a microenvironment with high CO₂ concentration around the electrode/electrolyte interface, which successfully suppresses the hydrogen evolution reaction (HER) of Ni foam. Consequently, the synthesized [P₆₆₆₁₄][triz]@Ni foam sample can obtain a CO product with 63% Faradaic efficiency from the ECR procedure, while no detectable CO can be found on pristine Ni foam. Owing to the superbase IL, the valency of Ni species retains Ni(I)/Ni(0) during electrolysis. Furthermore, the strikingly high CO₂ capacity by [P₆₆₆₁₄][Triz] (0.91 mol CO₂ per mole of IL) offers a high CO₂ local concentration in the reaction region. Theoretical calculations indicated that the neutral CO₂ molecule turned to be negatively charged with -0.546 e and changed into a bent geometry, thus rendering CO₂ activation and reduction in a low-energy pathway. This study provides a new method of electrode interface modification for the design of efficient ECR catalysts.

Bimetallic Cobalt–Copper Nanoparticle-Decorated Hollow Carbon Nanofibers for Efficient CO2 Electroreduction

Bimetallic materials are one of the most promising catalysts for the electrochemical reduction of CO₂, but there are still many challenges to be overcome on the route to industrialization. Herein, a series of carbon nanofiber-supported bimetallic cobalt–copper catalysts (Co_xCu_y/CFs) are designed and constructed through the electrospinning technique and a subsequent pyrolysis procedure. Small-sized Co–Cu nanoparticles are homogenously distributed on the porous carbon nanofibers, which can significantly improve the utilization rate of metal sites and greatly reduce the loading amount of metals. Moreover, different product distributions and catalytic performance can be obtained in CO₂ reduction via adjusting the metal proportion of Co_xCu_y/CFs. Especially, Co₃Cu/CFs can bring forth a 97% total faradaic efficiency (FE) of CO (68%) and HCOOH (29%) at –0.8 V_RHE cathode potential in 0.5 M KHCO₃ electrolyte. Furthermore, the hierarchical pores can firmly confine the small Co–Cu nanoparticles and keep them from easy agglomeration during electrolysis, eventually leading to 60 h of stability for Co₃Cu/CFs in CO₂ electroreduction. This study might provide a facile and economic method to fabricate efficient bimetallic catalysts for CO₂ electroreduction and other electrocatalysis applications.