Heading to Distributed Electrocatalytic Conversion of Small Abundant Molecules into Fuels, Chemicals, and Fertilizers

Abstract

The centralized production of fuels, chemicals, and fertilizers by thermocatalytic processes sustained by fossil resources is a pillar of modern societies. Electrocatalytic transformations of the abundant small molecules, water, carbon dioxide, dinitrogen, and methane, are emerging routes. Their coupling with renewable sources such as sun power may give rise to a distributed model based on small-scale reactors, so-called artificial leaves. Realizing this vision calls for improved catalytic performance, efforts on reactor and process engineering, and supportive regulatory frameworks. This work puts emphasis in analyzing the core challenge of catalytic performance by defining a common set of figures of merit. This analysis is nuanced by peculiarities inherent to the proposed scheme. This perspective thus aspires to (1) provide a bird's-eye view of the gap separating them from practical values, (2) identify sources of inefficiency, and (3) establish a qualitative comparison among their feasibility, resulting in H 2 O >> CO 2 R N 2 > CH 4 .Small Molecules as Building Blocks for Fuels, Chemicals, and Fertilizers Nature is inclined toward light elements developing complexity. Living beings are almost exclusively (99%) composed of only 4 elements: hydrogen, carbon, nitrogen, and oxygen. 1 This fact may be related to stable chemical bonds formed among them, a desirable property to build the complex molecules required for life (e.g., the typical C-C bond-dissociation energy is 360 kJ mol À1 in long-chain molecules). 2 Nevertheless, the stability of these bonds usually increases as the size of the molecules decrease, making dinitrogen (945 kJ mol À1 ), carbon dioxide (532 kJ mol À1 ), water (497 kJ mol À1 ), and methane (439 kJ mol À1 ) very stable end products. Water and carbon dioxide are energy deadends, in contrast to dinitrogen and especially methane, due to the reduced formal oxidation state of nitrogen and carbon atoms. These very abundant molecules are thus efficient and versatile platforms for storing renewable energy into fuels and/or producing valuable compounds for other uses.

Enabling storage and utilization of low-carbon electricity: power to formic acid

“…[327][328][329][330] This will enable the wide scale adoption of this technology and significant contribution towards carbon utilization towards value added products such as formic acid. 331,332 Thus far, we have covered a range of significant advances in eCO2RR, which have been accomplished by tuning reactions conditions such as system, solvent/electrolyte, operating pressure, pH, electrode, and catalyst. Thus far in the literature, these conditions have been independently optimized.…”

Engineering Heterostructured Nanocatalysts for CO2 Transformation Reactions: Advances and Perspectives

“…$1 kg H2 À 1 ). [165] Recently, Pérez-Ramírez and coworkers [166] employed life-cycle assessment (LCA) to assess the environmental impact of green methanol production from cradle to grave, including raw material acquisition (e. g., CO 2 , H 2 ), production process (including catalyst preparation), prod-ucts storage and transportation to final customers. They confirmed that the high expense (73 % of the total cost) of the renewable H 2 (e. g., H 2 O electrolysis powered by solar, wind, and nuclear energy, or biomass gasification) blocks the green methanol production effectively.…”

“…All in all, the present technoeconomic considerations are not religious enough, so we highlight the urgency for rigorous benchmarking studies and technoeconomic analyses to estimate the potential of these heterostructured materials for large-scale CO 2 conversion applications. [126,[165][166][167]…”

Hybridization of Fossil‐ and CO2‐Based Routes for Ethylene Production using Renewable Energy

“…Several studies performing techno-economic assessments of CCU technologies invariably conclude that they cannot compete in terms of production cost either under the current scenario or in the foreseeable future. [4,[12][13][14][15][16][17][18] Hence, there is a clear need to find a balance between fossil and (more sustainable) CCU technologies to ensure both the environmental and economic feasibility of the chemical industry. With this spirit, studies envision direct electroreduction of CO 2 and current fossil-based transformations as complementary in the mid-term toward a more decentralized production scheme or have analyzed examples of hybrid strategies involving electrocatalytic production of carbon monoxide in tandem with wellestablished Fischer-Tropsch processes [19,20] or methanol synthesis.…”

“…Even though the environmental performance of CCU processes is promising, their high cost still represents a significant barrier. Several studies performing techno‐economic assessments of CCU technologies invariably conclude that they cannot compete in terms of production cost either under the current scenario or in the foreseeable future [4,12–18] . Hence, there is a clear need to find a balance between fossil and (more sustainable) CCU technologies to ensure both the environmental and economic feasibility of the chemical industry.…”