Recent Advances in Metallic Catalyst Materials for Electrochemical Upgrading of Furfurals to Drop‐in Biofuels: A Mini Review

Abstract

The Paris Climate Agreement, signed by nearly every country of this world, aims to drastically reduce greenhouse gas emissions and be completely greenhouse gas neutral by 2050. [1] The Intergovernmental Panel on Climate Change identified greenhouse gases as one of the biggest contributors to climate change. [2] About 29% of the greenhouse gases of the U.S. in 2019 were distributed by the transportation sector. [3] On-road vehicles are responsible for about 75% of those emissions, aircrafts for about 9%. [3] The European Parliament and the Council of the European Union adopted the "Sustainable and Smart Mobility Strategy" in December 2020. [4] This strategy proposes several overhauls to the mobility sector of the European Union and highlights the need for carbonfree fuels. The most common biofuel is bioethanol (C 2 H 4 OH) and it is often used in blends with regular gasoline. In 2003, the flex-fuel era started first in Brazil, when all gasoline was blended with 25% ethanol. Germany was able to reduce the CO 2 emissions in 2020 by 13.2 million tons by using biofuel in lieu of fossil fuels. [5] E10 (10% ethanol mixed with 90% gasoline) emits 67%-96% less greenhouse gases compared to gasoline without any ethanol parts. [6] Ethanol blends are not without controversy and not all transportation vehicles can use an ethanol blend fuel; it can only be used by petrol-powered vehicles and models manufactured after 2011. [7] The strategy of utilizing of biofuel blends could be a simple way to reduce greenhouse gases in the transportation sector. [8,9] Specifically, the aviation sector strives for producing carbon neutral and cost-competitive synthetic biofuels which are "drop in", meaning that they are compatible with the existing aviation infrastructures. [10,11] These drop-in biofuels are alternative to traditional petroleum-based hydrocarbons (e.g., Jet A/A-1)) which can be used in "as is" in the present engines, either blended with the traditional fuels up to certain limits, or can be used even in unadulterated form. [12] Nevertheless, the synthesized blending components approved to date are not by themselves necessarily drop-in or interchangeable with Jet A/A-1, and so cannot be used as 100% synthesized fuels alone. To accomplish complete biofuels utilization into aviation sector, the produced biofuels needs to meet certain sustainability requirement to ascertain social, environmental, and economic performance. [13][14][15] Biokerosene, bioethanol, and other biofuels in general, are mostly produced by fermentation of energy crops such as sugar cane, and maize, which means that agriculture shifts toward fuel production instead of food production. In order to maximize the outcome, fertilizer is used which often contains/releases NO x

Steering Selectivity in Electrocatalytic Furfural Reduction via Electrode–Electrolyte Interface Modification

“…25,28 Hence, FF-to-FA conversion via the HAT process is preferentially conducted in a nonacidic solution, in a way to suppress FF-to-MF conversion (that is, via the PCET process), while FF-to-MF conversion is prone to be performed in acidic solution. 15,16 As a result, it remains difficult to steer FA and MF selectivities under the same reaction conditions. Furthermore, although FF-to-MF via the PCET process is more favorable in an acidic solution, FF-to-FA is promoted synchronously by facilitated proton transfer from the bulk to the catalyst surface via a hydrogen-bond (H-bond) network, resulting in low MF selectivity, not mentioning the competition of HER.…”

“…Conventionally, FF reduction to FA or MF relies on thermocatalysis, which is an energy-intensive process that requires high temperatures (80–400 °C) and explosive H 2 as the reducing agent. , The electrocatalytic approach has emerged as a potentially sustainable alternative for value-added chemical and fuel synthesis, with the advantages of employing renewable electricity, utilizing water as the hydrogen source, and operating at ambient conditions. − In recent years, significant advances have been achieved in the electrocatalytic reduction of FF. − In particular, electrocatalytic FF-to-FA conversion showed high selectivity (>90%) and Faradaic efficiency (FE, >80%) over copper (Cu)-based catalysts. − In contrast, achieving similar high selectivity for FF-to-MF remains challenging, owing to the competition with FF-to-FA conversion and hydrogen evolution reaction (HER), especially under high current density (Table S1).…”

“…This is not unreasonable, since electrocatalytic FF-to-FA and FF-to-MF conversions follow distinct pathways, unlike in thermocatalytic hydrogenolysis where FA is an intermediate to MF. , Regarding electrocatalytic FF-to-FA conversion (Figure b, left panel), it requires hydrogenation of the aldehyde group in FF mostly via a hydrogen atom transfer (HAT) process using adsorbed hydrogen atoms (H*), or a 2H + /2e – -involved proton-coupled electron transfer (PCET) process . While for electrocatalytic FF-to-MF conversion (Figure b, right panel), it necessitates hydrogenolysis of the aldehyde group in FF predominantly via a 4H + /4e – -involved PCET process. , The reactivity of the HAT process is influenced by the H* coverage on the electrode surface, which is facilitated by a decrease of electrolyte’s pH (which corresponds to the higher concentration of hydronium ions) and also affected by catalyst’s activity [which determines the reduction reactivity of H + (or H 2 O) to H*]. , In contrast, a PCET process was reported to be proportional to the concentration of hydronium ions and thus is favorable in a strong acid solution. , Hence, FF-to-FA conversion via the HAT process is preferentially conducted in a nonacidic solution, in a way to suppress FF-to-MF conversion (that is, via the PCET process), while FF-to-MF conversion is prone to be performed in acidic solution. , …”

Comparison of EV Consumption Based on Simulation of Real Driving Condition

“…Climate change is a pressing global issue, with greenhouse gases being identified as one of the major contributors to this phenomenon, the reduction of anthropologicrelated activity is now a priority for many policymakers [1]. The transportation sector, particularly in Europe, significantly impacts greenhouse gas emissions, with light-duty vehicles playing a substantial role, as today, transport emissions represent around 25% of the EU's total GHG emissions [2][3].…”

Exploring Impurity Effects and Catalyst Surface Features in Furfural Electroreduction for Jet Fuel Precursor Production: Experimental and Molecular Dynamics Insights

“…Another deterministic characteristic of electrochemical systems is the electrode roughness which influences the activity, selectivity and faradaic efficiency in electrocatalytic conversion by increasing the surface area and enhancing the electron transfer rate [27] . Scholten et al [28] .…”