Cobalt Spinel Nanocubes on N-Doped Graphene: A Synergistic Hybrid Electrocatalyst for the Highly Selective Reduction of Carbon Dioxide to Formic Acid

Abstract

Carbon dioxide reduction into useful chemical products is a key technology to address urgent climate and energy challenges. In this study, a nanohybrid made by Co3O4 and graphene is proposed as an efficient electrocatalyst for the selective reduction of CO2 to formate at low overpotential. A comparison between samples with different metal oxide to carbon ratios and with or without doping of the graphene moiety indicates that the most active catalyst is formed by highly dispersed and crystalline nanocubes exposing {001} oriented surfaces, whereas the nitrogen doping is critical to obtain a controlled morphology and to facilitate a topotactic transformation during electrocatalytic conditions to CoO, which results in the true active phase. The nanohybrid made up by intermediate loading of Co3O4 supported on nitrogen-doped graphene is the most active catalyst, being able to produce 3.14 mmol of formate in 8 h at −0.95 V vs SCE with a Faradaic efficiency of 83%.

Bi2O3 Nanosheets Grown on Multi‐Channel Carbon Matrix to Catalyze Efficient CO2 Electroreduction to HCOOH

“…For comparison, the electrocatalytic activities of the other three samples, physically mixed Bi 2 O 3 NSs (Supporting Information, Figure S11) and MCCM (designated as Bi 2 O 3 NSs/MCCM), Bi 2 O 3 NSs grown on solid carbon matrix (designated as Bi 2 O 3 NSs@SCM) and MCCM, were also evaluated for CO 2 RR. The cathodic polarization curves in Figure a indicate that the MCCM is indeed active for CO 2 RR and contributes a j of −8.5 mA cm −2 at the potential of −1.355 V, whereas the Bi 2 O 3 NSs@MCCM achieves a remarkably high j of −19.3 mA cm −2 , exceeding Bi 2 O 3 NSs/MCCM, Bi 2 O 3 NSs@SCM, and most of the state‐of‐the‐art materials for HCOOH formation . However, the total j of Bi 2 O 3 NSs@MCCM recorded in the polarization curve cannot be completely attributed to the CO 2 RR catalytic activity since HER always proceeds competitively with CO 2 RR upon testing, especially in aqueous solution.…”

Interfacial Chemistry of Low‐Dimensional Systems for Applications in Nanocatalysis

“…Through the review of several types of different systems such as interfaces with metals, oxides, and 2D materials, we have demonstrated how general this behavior is and how relevant it can be in the field of chemical conversion and catalysis. We have provided several examples ranging from redox chemistry, to biomimetic catalysis and electrochemistry . The common trait in all of these cases is the ability of the interfaces to make available at a very convenient energy cost the electrons that are necessary for an elementary step of a more complex reaction.…”

“…Another interesting system where the interface plays a major role is cobalt oxide supported on nitrogen doped graphene …”

“…Using this approach, excellent catalyst for the ORR and OER have been synthesized in the course of past years , . Following this route and using the hydrothermal method, we prepared several cobalt spinel/graphene composites to be used as catalysts for the CO 2 reduction reaction . As support we used both graphene oxide and nitrogen doped graphene and optimized the synthesis conditions in order to obtain highly dispersed and morphology controlled spinel cobalt oxide nanoparticles.…”

“…(d) Faradaic efficiency to formate at different potentials for the graphene‐Co 3 O 4 nanocomposites. Adapted with permission from ref …”