Electrocatalytic oxidation of 5-hydroxymethylfurfural (HMF) to 2,5-furandicarboxylic acid (FDCA), a sustainable strategy to produce bio-based plastic monomer, is always conducted in a high-concentration alkaline solution (1.0 mol L-1 KOH) for high activity. However, such high concentration of alkali poses challenges including HMF degradation and high operation costs associated with product separation. Herein, we report a single-atom-ruthenium supported on Co3O4 (Ru1-Co3O4) as a catalyst that works efficiently in a low-concentration alkaline electrolyte (0.1 mol L-1 KOH), exhibiting a low potential of 1.191 V versus a reversible hydrogen electrode to achieve 10 mA cm-2 in 0.1 mol L-1 KOH, which outperforms previous catalysts. Electrochemical studies demonstrate that single-atom-Ru significantly enhances hydroxyl (OH-) adsorption with insufficient OH- supply, thus improving HMF oxidation. To showcase the potential of Ru1-Co3O4 catalyst, we demonstrate its high efficiency in a flow reactor under industrially relevant conditions. Eventually, techno-economic analysis shows that substitution of the conventional 1.0 mol L-1 KOH with 0.1 mol L-1 KOH electrolyte may significantly reduce the minimum selling price of FDCA by 21.0%. This work demonstrates an efficient catalyst design for electrooxidation of biomass working without using strong alkaline electrolyte that may contribute to more economic biomass electro-valorization.

The electrochemical oxidation of biomass molecules coupling with hydrogen production is a promising strategy to obtain both green energy and value-added chemicals; however, this strategy is limited by the competing oxygen evolution reactions and high energy consumption. Herein, we report a hierarchical CoNi layered double hydroxides (LDHs) electrocatalyst with abundant Ni vacancies for the efficient anodic oxidation of 5-hydroxymethylfurfural (HMF) and cathodic hydrogen evolution. The unique hierarchical nanosheet structure and Ni vacancies provide outstanding activity and selectivity toward several biomass molecules because of the finely regulated electronic structure and highly-exposed active sites. In particular, a high faradaic efficiency (FE) at a high current density (99% at 100 mA cm-2) is achieved for HMF oxidation, and a two-electrode electrolyzer is assembled based on the Ni vacancies-enriched LDH, which realized a continuous synthesis of highly-pure 2,5-furandicarboxylic acid products with high yields (95%) and FE (90%).

As a sustainable valorization route, electrochemical glycerol oxidation reaction (GOR) involves in formation of key OH* and selective adsorption/cleavage of C-C(O) intermediates with multi-step electron transfer, thus suffering from high potential and poor formate selectivity for most non-noble-metal-based electrocatalysts. So, it remains challenging to understand the structure-property relationship as well as construct synergistic sites to realize high-activity and high-selectivity GOR. Herein, we successfully achieve dual-high performance with low potentials and superior formate selectivity for GOR by forming synergistic Lewis and Brønsted acid sites in Ni-alloyed Co-based spinel. The optimized NiCo oxide solid-acid electrocatalyst exhibits low reaction potential (1.219 V@10 mA/cm2) and high formate selectivity (94.0 %) toward GOR. In situ electrochemical impedance spectroscopy and pH-dependence measurements show that the Lewis acid centers could accelerate OH* production, while the Brønsted acid centers are proved to facilitate high-selectivity formation of formate. Theoretical calculations reveal that NiCo alloyed oxide shows appropriate d-band center, thus balancing adsorption/desorption of C-O intermediates. This study provides new insights into rationally designing solid-acid electrocatalysts for biomass electro-upcycling.

Electrochemical oxidation of biomass-based 5-hydroxymethylfurfural (HMF) is an effective approach for achieving the high-value products of 2,5-furandicarboxylic acid (FDCA). However, the restricted formation of high-valence metal active species for electrocatalysts results in a sluggish kinetic process of HMF oxidation reaction (HMFOR). Herein, we fabricated the Ni3+-rich cross-linked α-Ni(OH)2 nanosheets for accelerating the HMFOR through an anion-mediated strategy. It is identified that the Cl- ions with strong penetrability replace a portion of lattice oxygen atoms in α-Ni(OH)2 to form Ni-Cl bonds, contributing to breaking the inherent lattice order and generating a special Ni3+-rich structure. Owing to the promoted adsorption and accelerated oxidation of hydroxyl and aldehyde groups by the affluent Ni3+ active species, the large oxidation current density of 116.5 mA cm-2 and HMFOR kinetic constant of 0.067 min-1 has been achieved at 1.45 V (vs. RHE). By analyzing the oxidation products, the FDCA yield and Faradic efficiency are both higher than 99.25 % and 99.36 % for five successive determinations. Therefore, this work provides an insightful anion-mediated strategy for designing high-performance electrocatalysts for biomass conversion application.

Alanine is widely employed for synthesizing polymers, pharmaceuticals, and agrochemicals. Electrocatalytic coupling of biomass molecules and waste nitrate is attractive for the nitrate removal and alanine production under ambient conditions. However, the reaction efficiency is relatively low due to the activation of the stable substrates, and the coupling of two reactive intermediates remains challenging. Herein, we realize the integrated tandem electrochemical-chemical-electochemical synthesis of alanine from the biomass-derived pyruvic acid (PA) and waste nitrate (NO3 - ) catalyzed by PdCu nano-bead-wires (PdCu NBWs). The overall reaction pathway is demonstrated as a multiple-step catalytic cascade process via coupling the reactive intermediates NH2 OH and PA on the catalyst surface. Interestingly, in this integrated tandem electrochemical-chemical-electrochemical catalytic cascade process, Cu facilitates the electrochemical reduction of nitrate to NH2 OH intermediates, which chemically couple with PA to form the pyruvic oxime, and Pd promotes the electrochemical reduction of pyruvic oxime to the desirable alanine. This work provides a green strategy to convert waste NO3 - to wealth and enriches the substrate scope of renewable biomass feedstocks to produce high-value amino acids.

Electricity-driven organo-oxidations have shown an increasing potential recently. However, oxygen evolution reaction (OER) is the primary competitive reaction, especially under high current densities, which leads to low Faradaic efficiency (FE) of the product and catalyst detachment from the electrode. Here, we report a bimetallic Ni-Cu electrocatalyst supported on Ni foam (Ni-Cu/NF) to passivate the OER process while the oxidation of 5-hydroxymethylfurfural (HMF) is significantly enhanced. A current density of 1000 mA cm-2 can be achieved at 1.50 V vs. reversible hydrogen electrode, and both FE and yield keep close to 100 % over a wide range of potentials. Both experimental results and theoretical calculations reveal that Cu doping impedes the OH* deprotonation to O* and hereby OER process is greatly passivated. Those instructive results provide a new approach to realizing highly efficient biomass upgrading by regulating the OER activity.

To date the electroactive species of selective aldehyde oxidation to carboxylates at gold electrodes is usually assumed to be the diolate. It forms with high concentration only in very alkaline electrolytes, when OH- binds to the carbonyl carbon atom. Accordingly, the electrochemical upgrading of biomass-derived aldehydes to carboxylates is believed to be limited to very alkaline electrolytes at many electrode materials. However, OH- -induced aldehyde decomposition in these electrolytes prevents application of electrochemical aldehyde oxidation for the sustainable upgrading of biomass to value-added chemicals at industrial scale. Here, we demonstrate the successful oxidation of aliphatic aldehydes at a rotating gold electrode at pH 12, where only 1 % of the aldehyde resides as the diolate species. This concentration is too small to account for the observed current, which shows that also other aldehyde species (i. e., the geminal diol and the non-hydrated aldehyde) are electroactive. This insight allows developing strategies to omit aldehyde decomposition while achieving high current densities for the selective aldehyde oxidation, making its future industrial application viable.

The development of a rechargeable battery that can produce valuable chemicals in both electricity storage and generation processes holds great promise for increasing the electron economy and economic value. However, this battery has yet to be explored. Herein, we report a biomass flow battery that generates electricity while producing furoic acid, and store electricity while yielding furfuryl alcohol. The battery is composed of a rhodium-copper (Rh1 Cu) single-atom alloy as anode, a cobalt-doped nickel hydroxide (Co0.2 Ni0.8 (OH)2 ) as cathode, and furfural-containing anolyte. In a full battery evaluation, this battery displays an open circuit voltage (OCV) of 1.29 V and a peak power density up to 107 mW cm-2 , surpassing most catalysis-battery hybrid systems. As a proof-of-concept, we demonstrate that this battery produces 1 kg furoic acid with 0.78 kWh electricity output, and yields 0.62 kg furfuryl alcohol when 1 kWh electricity is stored. This work may shed light on the design of rechargeable batteries with value-added functionality such as chemicals production.

Refiners around the globe are either considering or are actively replacing a portion of their crude oil inputs originating from fossil sources with alternative sources, including recycled materials (plastics, urban waste, mixed solid waste) and renewable materials (bio-mass waste, vegetable oils). In this paper, we explore such replacement, specifically focusing on the fluid catalytic cracking (FCC) operation. Five pyrolysis oils, obtained from municipal solid waste (MSW) and biogenic material (olive stones/pits), were fully characterized and tested at 10% loading against a standard fluid catalytic cracking (FCC) vacuum gasoil (VGO) feed in a bench scale reactor using an industrially available fluid catalytic cracking catalyst based on ultrastable Y zeolite to simulate fluid catalytic cracking co-processing. Despite having unique feed properties, including high Conradson carbon (e.g., up to 19.41 wt%), water (e.g., up to 5.7 wt%), and contaminants (e.g., up to 227 ppm Cl) in some cases, the five pyrolysis oils gave similar yield patterns as vacuum gasoil. Gasoline was slightly (ca. 1 wt%) higher in all cases and LPG slightly (ca. 1 wt%) lower. Olefinicity in the LPG streams were unchanged, bottoms and light cycle oil (LCO) showed no significant changes, while dry gas was slightly (up to -0.2 wt%) lower. Coke selectivity was also unchanged (maximum -7.7 wt%, relatively), suggesting minimal to no heat balance concerns when co-processing in an industrial fluid catalytic cracking unit. The results demonstrate the applicability of municipal solid waste and biogenic originating pyrolysis oils into a refinery. A catalyst design concept is explored, based on higher rare Earth oxide exchange and/or utilization of ZSM-5 zeolite, that would further minimize the impacts of replacing fossil oils with pyrolysis oils, namely one that shifts the 1% higher gasoline into LPG.

Electrocatalytic biomass upgrading has proven to be an effective technique for generating value-added products. Herein, the design and development of furfural upgrading using transition-metal borides (MBenes) with simultaneous production of hydrogen are presented. Using density functional theory, the stabilities, selectivities, and activities of 13 MBene candidates are systematically evaluated for furfural upgrading. This research suggests that Fe2 B2 can serve as a promising electrocatalyst for the formation of furoic acid (FAC), with a limiting potential of -0.15 V, and 5-hydroxy-2(5H)-furanone (HFO), with a limiting potential of -0.93 V. Furthermore, Fe2 B2 and Mn2 Fe2 are shown to exhibit favorable limiting potentials of -1.35 and -1.36 V, respectively, for producing 6-hydroxy-2.3-dihydro-6H-pyrano-3-one (HDPO), indicating that they may also serve as electrocatalysts. Based on Sabatier\'s principle, a descriptor (φ) of material properties is developed for screening catalysts with high catalytic activity considering the electronegativities and d-electron number of metals. Additionally, surface redox potential, electronic properties, and charge-density differences are determined for Fe2 B2 , which is estimated to exhibit high catalytic activity for the oxidation of furfural to FAC and HFO.