The electrochemical reduction of carbon dioxide (CO2) has received significant attention in academic research, although the techno-economic prospects of the technology for the large-scale production of chemicals are unclear. In this work, we briefly reviewed the current state-of-the-art CO2 reduction figures of merit, and performed an economic analysis to calculate the end-of-life net present value (NPV) of a generalized CO2 electrolyzer system for the production of 100 tons/day of various CO2 reduction products. Under current techno-economic conditions, carbon monoxide and formic acid were the only economically viable products with NPVs of $13.5 million and $39.4 million, respectively. However, higher-order alcohols, such as ethanol and n-propanol, could be highly promising under future conditions if reasonable electrocatalytic performance benchmarks are achieved (e.g., 300 mA/cm2 and 0.5 V overpotential at 70% Faradaic efficiency). Herein, we established performance targets such that if these targets are achieved, electrochemical CO2 reduction for fuels and chemicals production can become a profitable option as part of the growing renewable energy infrastructure.

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fine control of production rates, wide scalability of modular electrolyzer designs, and the potential to produce a variety of high-value products. [7][8][9] More importantly, this technology can be readily powered by carbon-free energy sources such as wind, solar, and nuclear, providing a zero-CO 2 emission (or even negative) pathway for commodity chemical production. A recent scientific study on photovoltaic (PV) clearly showed a decrease of PV electricity price over time with a projected PV electricity price as low as $0.03 per kWh in the near future. [10] A similar trend also holds for wind energy with an electricity price already being ≈$0.02 per kWh. [11] Thus, the low electricity price makes electrochemically driven CO 2 utilization technologies potentially profitable for commercial applications. [12] Recent studies in electrocatalytic CO 2 reduction have been primarily focused on high-value multicarbon (C 2+ ) products, such as ethylene, ethanol, and n-propanol. [13][14][15][16] Among all the catalysts, copper (Cu) is the most widely studied CO 2 reduction catalyst with a relatively high C 2+ selectivity. [17][18][19][20][21] Therefore, many efforts have been devoted to exploring nanostructured Cu catalysts such as nanoparticles, [14,22,23] nanofoam, [24,25] nanowires, [26,27] and nanopores [28] to further elucidate the structure-property correlation for CO 2 reduction over Cu catalysts. However, most of these investigations are typically performed in batchcell configurations which have some technical limitations. For example, the low solubility of CO 2 in electrolyte (usually an aqueous solution) greatly limits the maximum CO 2 reduction current density to ≈40 mA cm −2 , making it difficult to examine catalytic behavior at more practical current densities (>200 mA cm −2 ). [29,30] In addition, because batch-cell type studies often utilize CO 2 saturated electrolytes, it is not possible to use alkaline electrolytes because hydroxide ions strongly react with dissolved CO 2 to form carbonates. In order to overcome these challenges associated with batch-cell type configurations, a flow cell configuration can be utilized, [31] which has been recently demonstrated for silver catalyzed CO 2 reduction to CO. [32,33] Despite these efforts, there is currently no systematic flow cell study on how nanostructuring and electrolyte can affect CO 2 reduction properties of Cu catalysts, especially in alkaline electrolytes.In this work, we synthesized a nanoporous Cu catalyst with a pore size of 100-200 nm and examined its catalytic properties for CO 2 reduction in a microfluidic electrolysis cell. At an applied Electrochemical reduction of carbon dioxide (CO 2 ) is an appealing approach toward tackling climate change associated with atmospheric CO 2 emissions. This approach uses CO 2 as the carbon feedstock to produce value-added chemicals, resulting in a carbon-neutral (or even carbon-negative) process for chemical production. Many efforts have been devoted to the development of CO 2 electrolysis devices that can be oper...

Converting greenhouse gas carbon dioxide (CO) to value-added chemicals is an appealing approach to tackle CO emission challenges. The chemical transformation of CO requires suitable catalysts that can lower the activation energy barrier, thus minimizing the energy penalty associated with the CO reduction reaction. First-row transition metals are potential candidates as catalysts for electrochemical CO reduction; however, their high oxygen affinity makes them easy to be oxidized, which could, in turn, strongly affect the catalytic properties of metal-based catalysts. In this work, we propose a strategy to synthesize Ag-Sn electrocatalysts with a core-shell nanostructure that contains a bimetallic core responsible for high electronic conductivity and an ultrathin partially oxidized shell for catalytic CO conversion. This concept was demonstrated by a series of Ag-Sn bimetallic electrocatalysts. At an optimal SnO shell thickness of ∼1.7 nm, the catalyst exhibited a high formate Faradaic efficiency of ∼80% and a formate partial current density of ∼16 mA cm at -0.8 V vs RHE, a remarkable performance in comparison to state-of-the-art formate-selective CO reduction catalysts. Density-functional theory calculations showed that oxygen vacancies on the SnO (101) surface are stable at highly negative potentials and crucial for CO activation. In addition, the adsorption energy of CO at these oxygen-vacant sites can be used as the descriptor for catalytic performance because of its linear correlation to OCHO* and COOH*, two critical intermediates for the HCOOH and CO formation pathways, respectively. The volcano-like relationship between catalytic activity toward formate as a function of the bulk Sn concentration arises from the competing effects of favorable stabilization of OCHO* by lattice expansion and the electron conductivity loss due to the increased thickness of the SnO layer.

Understanding reaction pathways and mechanisms for electrocatalytic transformation of small molecules (e.g., H2O, CO2, and N2) to value-added chemicals is critical to enabling the rational design of high-performing catalytic systems. Tafel analysis is widely used to gain mechanistic insights, and in some cases, has been used to determine the reaction mechanism. In this Perspective, we discuss the mechanistic insights that can be gained from Tafel analysis and its limitations using the simplest two-electron CO2 reduction reaction to CO on Au and Ag surfaces as an example. By comparing and analyzing existing as well as additional kinetic data, we show that the Tafel slopes obtained on Au and Ag surfaces in the kinetically controlled region (low overpotential) are consistently ∼59 mV dec–1, regardless of whether catalysts are polycrystalline or nanostructured in nature, suggesting that the initial electron transfer (CO2 + e– → CO2 –) is unlikely to be the rate-limiting step. In addition, we demonstrate how initial mechanistic assumptions can dictate experimental design, the result of which could in turn bias mechanistic interpretations. Therefore, as informative as Tafel analysis is, independent experimental and computational techniques are necessary to support a proposed mechanism of multielectron electrocatalytic reactions, such as CO2 reduction.

Electrochemical conversion of carbon dioxide (CO2) to value-added chemicals has attracted much attention in recent years as a potential alternative to fossil resources. Although significant works have studied the influence of impurities in the electrolyte (e.g., metal ions), few studies have been performed to understand the influence of gaseous impurities in CO2 electroreduction. Herein, we study the effects of sulfur dioxide (SO2) on Ag-, Sn-, and Cu-catalyzed CO2 electrolysis in a flow-cell electrolyzer in near-neutral electrolyte, representing a broad range of CO2 reduction catalysts. We show that the presence of SO2 impurity reduces the efficiency of converting CO2 due to the preferential reduction of SO2. In the cases of Ag and Sn, the effect of SO2 impurity was reversible and the catalytic activities of both catalysts were recovered. On the contrary, a shift in selectivity toward formate accompanied by a suppression of multicarbon (C2+) products was observed on Cu catalyst, demonstrating that Cu is highly sensitive to SO2 impurity. Our results suggest that CO2 obtained from direct air capture technologies or biorefineries could be more suitable for Cu-catalyzed CO2 electrolysis as these CO2 sources would be relatively cleaner (SO2-free) than fossil-derived sources such as power plants and can be directly coupled with distributed renewable energy sources such as wind and solar.

Bimetallics are emerging as important materials that often exhibit distinct chemical properties from monometallics. However, there is limited access to homogeneously alloyed bimetallics because of the thermodynamic immiscibility of the constituent elements. Overcoming the inherent immiscibility in bimetallic systems would create a bimetallic library with unique properties. Here, we present a nonequilibrium synthesis strategy to address the immiscibility challenge in bimetallics. As a proof of concept, we synthesize a broad range of homogeneously alloyed Cu-based bimetallic nanoparticles regardless of the thermodynamic immiscibility. The nonequilibrated bimetallic nanoparticles are further investigated as electrocatalysts for carbon monoxide reduction at commercially relevant current densities (>100 mA cm−2), in which Cu0.9Ni0.1 shows the highest multicarbon product Faradaic efficiency of ~76% with a current density of ~93 mA cm−2. The ability to overcome thermodynamic immiscibility in multimetallic synthesis offers freedom to design and synthesize new functional nanomaterials with desired chemical compositions and catalytic properties.