Highly Efficient Electrochemical CO₂ Reduction Reaction to CO with One‐Pot Synthesized Co‐Pyridine‐Derived Catalyst Incorporated in a Nafion‐Based Membrane Electrode Assembly

Abstract

hindered because the corresponding reaction requires only two electrons and two protons, making it a promising initial feedstock. [19] Recent studies have described high (>90%) Faradaic efficiency (FE) for CO 2 RR to CO at high current density (>50 mA cm −2) for several different catalysts. [20-23] Among catalysts, metaldoped carbon materials have emerged at the intersection between heterogeneous carbon and metal microcycles, showing high selectivity toward CO 2 RR to CO. [23-38] Despite the wide variety of structural designs, most catalysts were shown to promote CO 2 RR only in CO 2-saturated basic or neutral aqueous solution to suppress the competing hydrogen evolution reaction (HER). Another underlying challenge is that the synthetic procedures often require relatively complicated steps such as templating. Such constraints impose practical difficulties and additional costs for operation. As seen in fuel-cell technology, a membrane electrode assembly (MEA) offers technical advantages in terms of scalability, design flexibility, and ease of operation. [39] However, only a few studies have demonstrated CO 2 RR with MEAs with either cation-exchange [25,36,40,41] or anion-exchange membranes. [37,42,43] While cation-exchange based MEAs face a fundamental challenge due to the competing HER because of the acidic environment, they have great potential for commercialization because of their highly durable and widely available components. [44] Herein, we describe a straightforward one-pot synthesis of cobalt and organic [poly-4-vinylpyridine (P4VP)] precursors with carbon supports to form the cathode of a highly effective nafion-based MEA, using the synergy between the reduced cobalt and pyridine moieties to drive the CO 2 RR. Studies indicate that the catalyst performed CO 2 RR predominantly over HER across a wide range of pH. Optimization of the catalyst components led to CO production with 92% FE and 58% EE at 85 mA cm −2 , and preliminary durability tests showed stable FE for 20 h of operation. Metal-pyridine derived carbon catalysts were synthesized according to the reported pyrolysis method as illustrated in Figure 1a. [25,36] Metal (Co, Fe, and Ni) nitrate and pyridine derivatives [4-ethylpyridine (EPy), 4-aminopyridine (APy), poly-4-vinylpyridine (P4VP), and poly-2-vinylpyridine (P2VP)], There is great need for the development of an electrochemical CO 2 reduction reaction (CO 2 RR) process with high Faraday efficiency (FE), energy efficiency (EE), and current density for practical utilization of CO 2. Here, a facile one-pot synthesis of a catalyst is reported that is based on cobalt and poly-4-vinylpyridine that can perform CO 2 RR to CO predominantly with respect to the hydrogen evolution reaction in a nafion-based membrane electrode assembly and can work in pH ranging from 2 to 7. Cell optimization results in CO 2 RR to CO with 92% FE and 58% EE at 85 mA cm −2 , while showing no noticeable degradation in FE at 20 h. These characteristics are attributed to synthesis and processing conditions which promote nearly...

Effects of the Catalyst Dynamic Changes and Influence of the Reaction Environment on the Performance of Electrochemical CO2 Reduction

“…[12][13][14][15] In addition to the catalyst development, the design and optimization of reactors for CO 2 R give another route to enhance the catalytic efficiency. [16][17][18][19][20][21] Nevertheless, the industrialization of the CO 2 R is still inhibited by its unsatisfactory activity, selectivity, and durability, particularly for multi-carbon (C 2+ ) products.One major difficulty for controlling electrochemical CO 2 R is that, its reaction pathways and reactivity are highly sensitive to the catalyst-active-site identity and the local reaction environment. [22] Even minor changes of the catalyst-electrolyte interface occurred during the electrocatalysis can substantially influence the overall catalytic performance.…”

“…[12][13][14][15] In addition to the catalyst development, the design and optimization of reactors for CO 2 R give another route to enhance the catalytic efficiency. [16][17][18][19][20][21] Nevertheless, the industrialization of the CO 2 R is still inhibited by its unsatisfactory activity, selectivity, and durability, particularly for multi-carbon (C 2+ ) products.…”

Acidic Electrocatalytic CO2 Reduction Using Space-Confined Nanoreactors

“… The fitting of XPS shows that the content of nitrogen in Ni 5 @NCN is 16.9 wt %, revealing the N-rich feature, which could increase metal loading (Table S1). As shown in Figure d, the deconvolution of the N 1s high-resolution spectrum of Ni 5 @NCN shows four main species including pyridinic (398.2 eV), pyrrolic (399.5 eV), graphitic (400.9 eV), and oxidized types (403.4 eV) of nitrogen. , At lower preparation temperature of 400 °C, the metal-N bonding was not formed and thus cannot be detected by XPS …”

Heterogeneous Catalysis for CO2 Conversion into Chemicals and Fuels

“…Moreover, carbonate can transfer to the anode through the anion exchange membrane, thereby leading to significant carbon loss and a low CO 2 utilization efficiency [176,177]. Possible strategies for dealing with the carbonate issue are to use a cation exchange membrane, bipolar membrane, and solid electrolyte buffer layer [168, 169,[178][179][180]. This leads to an emerging direction, i.e., acid CO 2 electrolysis that has been demonstrated to suppress carbonate formation [181][182][183][184].…”