Electrocatalytic Upcycling of Biomass and Plastic Wastes to Biodegradable Polymer Monomers and Hydrogen Fuel at High Current Densities

Shell-like Ni(OH)2 loaded with Pd nanoparticle catalyst mediated efficient electrocatalytic upcycling of polyethylene terephthalate plastics to glycolic acid

Electrochemical techniques offer a promising approach to achieving plastic waste recycling, particularly to address plastic pollution problems. In this study, we developed a novel Pd/Ni(OH)2/NF electrocatalyst. with efficient interfacial electron transfer capability in the conversion of ethylene glycol (EG) to high-value-added glycolic acid (GA) from the hydrolyzed product of polyethylene terephthalate (PET) plastics. This Pd/Ni(OH)2/NF electrocatalyst demonstrated low overpotentials of 0.53 V and 0.79 V vs. RHE and achieved current densities of 10 mA cm-2 and 100 mA cm-2, respectively. Notably, Pd/Ni(OH)2/NF electrocatalyst can efficiently produce value-added glycolic acid over a wide potential range (0.9 V-1.3 V), with a maximum Faraday efficiency rate of 94.2 %. The low overpotential and high efficiency of Pd/Ni(OH)2/NF is attributed to the strong electronic interaction at the Pd/Ni(OH)2 interface, which enhances the catalytic conversion of the ethylene glycol. Density functional theory (DFT) calculations provide further theoretical insights into the transformation mechanisms. Additionally, the catalyst demonstrated stable electrocatalytic performance for 100 h in an anion-exchange membrane (AEM) flow reactor at a current density of 100 mA cm-2. This study presents a novel electrocatalyst and viable electrochemical pathway for upgrading PET plastic waste into valuable products.

Geography-guided industrial-level upcycling of polyethylene terephthalate plastics through alkaline seawater-based processes

The escalating plastic crisis can be mitigated by upgrading waste polyethylene terephthalate (PET). Leveraging the geographical advantages of offshores with established chlor-alkali industries, abundant renewable energy, and extensive seawater, we here present a technically and economically viable strategy of harnessing natural seawater as a medium to transform PET plastics into high-value chemicals. We report a nickel-molybdenum catalyst incorporating frustrated Lewis pairs for the efficient breakage of C─C bond and the oxidation of ethylene glycol, which sustains a current of 6 amperes at 1.74 volts over 350 hours, with a projected revenue of approximately $304 United States dollar (USD) per ton of processed PET plastics. In a customized electrolyzer, we successfully convert 301.0 grams of waste PET into 227.1 grams of p-phthalic acid (95.5% yield), 1486.2 grams of potassium diformate (67.2% yield), and approximately 214.9 liters of green hydrogen. This study paves the way for scalable PET upcycling, contributing to a circular economy and mitigating the plastic pollution crisis.

Efficient Electrochemical-Enzymatic Conversion of PET to Formate Coupled with Nitrate Reduction Over Ru-Doped Co3O4 Catalysts

Electrochemical reforming presents a sustainable route for the conversion of nitrate (NO3 -) and polyethylene terephthalate (PET) into value-added chemicals, such as ammonia (NH3) and formic acid (HCOOH). However, its widespread application has been constrained by low selectivity due to the complexity of reduction processes and thus energy scaling limitations. In this study, the atomically dispersed Ru sites in Co3O4 synergistically interact with Co centers, facilitating the adsorption and activation of hydroxyl radicals (OH*) and ethylene glycol (EG), resulting in a remarkable HCOOH selectivity of 99% and a yield rate of 11.2 mmol h-1 cm-2 surpassing that of pristine Co3O4 (55% and 3.8 mmol h-1 cm-2). Furthermore, when applied as a bifunctional cathode catalyst, Ru-Co3O4 achieves a remarkable Faradaic efficiency (FE) of 98.5% for NH3 production (3.54 mmol h-1 cm-2) at -0.3 V versus RHE. Additionally, we developed a prototype device powered by a commercial silicon photovoltaic cell, enabling on-site solar-driven production of formate and NH3 through enzyme-catalyzed PET and NO3 - conversion. This study offers a viable approach for waste valorization and green chemical production, paving the way for sustainable energy applications.

In Situ Construction of N-Doped Ni3S2@Ni(OH)2 Self-Supported Heterostructures for Highly Selective Electrooxidation of 5-Hydroxymethylfurfural to 2,5-Diformylfuran

The selective electrooxidation of 5-hydroxymethylfurfural (HMF) to 2,5-diformylfuran (DFF) is promising for biomass valorization but remains challenging under alkaline conditions due to inefficient nonprecious metal catalysts. Herein, we develop a scalable N-doped Ni3S2@Ni(OH)2 heterostructure via a molten-salt-derived precursor and a one-pot hydrothermal synthesis. This catalyst achieves a low potential of 1.395 V (10 mA cm-2) and 96% DFF selectivity, with a 47.6% yield in 1.0 M K2CO3 (pH = 12). Experimental and DFT studies reveal that interfacial electron redistribution enhances HMF and hydroxyl radical adsorption, lowers the HMF-to-DFF energy barrier, and accelerates charge transfer. The hydroxyl group in HMF is more reactive than the aldehyde, boosting the DFF selectivity. The heterojunction's synergistic effect is key to achieving high-value aldehydes efficiently.

Synergy between multi-components and Ir dopant in Ir-doped high-entropy alloy nanoparticles for efficient and robust ethylene glycol electro-oxidation at an industrial-level current

Electrochemical oxidation of crude ethylene glycol (EG) to commodity chemicals and H2, powered by renewables energy, is a sustainable and promising strategy for upcycling the end-of-life polyethylene terephthalate (PET) wastes. Pt/Pd group noble metals are deemed as state-of-the-art catalysts for the EG electro-oxidation reaction (EGOR). However, these catalysts suffer from high affinity of the carbonyl intermediates, which consequently results in poisoning of active sites and poor electrochemical stability. Herein, we designed and synthesized small-sized PdPtAuNiCu and Ir-doped PdPtAuNiCu high-entropy alloy nanoparticles (abbreviated as PdPtAuNiCu and Ir-PdPtAuNiCu HEANs, respectively) via a wet chemical method. Benefiting from the multisite synergy and Ir dopant, the as-synthesized Ir-PdPtAuNiCu HEANs achieved selective and robust EGOR to glycolate (GA) in alkaline medium with a high mass activity of 2.41 A mg-1 at 0.724 V versus reversible hydrogen electrode (vs. RHE) and a glycolate Faradaic efficiency (FEGA) of 88.8%. In a home-made membrane-free flow electrolyzer assembled with this bifunctional catalyst [(-)PdPtAuNiCu∥Ir-PdPtAuNiCu(+)], ultra-stable EGOR was realized beyond 1200 h at an industrial-level current density of >300 mA cm-2 under a low voltage of 0.724 V. These findings provide a new paradigm for designing efficient and robust EGOR catalysts that can supersede other electrocatalysts for practical applications.

Electrochemical Hydrogen Production Coupling with the Upgrading of Organic and Inorganic Chemicals

Electrocatalytic water splitting powered by renewable energy is a green and sustainable method for producing high-purity H2. However, in conventional water electrolysis, the anodic oxygen evolution reaction (OER) involves a four-electron transfer process with inherently sluggish kinetics, which severely limits the overall efficiency of water splitting. Recently, replacing OER with thermodynamically favorable oxidation reactions, coupled with the hydrogen evolution reaction, has garnered significant attention and achieved remarkable progress. This strategy not only offers a promising route for energy-saving H₂ production but also enables the simultaneous synthesis of high-value-added products or the removal of pollutants at the anode. Researchers successfully demonstrate the upgrading of numerous organic and inorganic alternatives through this approach. In this review, the latest advances in the coupling of electrocatalytic H2 production and the upgrading of organic and inorganic alternative chemicals are summarized. What's more, the optimization strategy of catalysts, structure-performance relationship, and catalytic mechanism of various reactions are well discussed in each part. Finally, the current challenges and future prospects in this field are outlined, aiming to inspire further innovative breakthroughs in this exciting area of research.

Research progress of transition metal catalysts for electrocatalytic EG oxidation

Ethylene glycol (EG) is a small-molecule alcohol with a low oxidation potential and is a key monomer in the production of polyethylene terephthalate (PET). The efficient oxidation of EG can further enable the recycling of waste PET. Currently, there are many studies on catalysts for EG oxidation, among which transition metal catalysts (including traditional non-precious metals such as Fe, Co, Ni and other noble metals such as Pt and Pd) have good prospects for application in EG oxidation reactions due to their unique electronic structures. In this study, the synthesis strategy of transition metal catalysts for the electrocatalytic oxidation of EG is summarized and the performance of different types of catalysts in the EG oxidation reaction is reviewed. Advanced characterization methods were used to understand the oxidation mechanism of EG and to control the conversion of EGOR intermediates into target products. Therefore, we need to further explore efficient catalysts for EG oxidation to achieve efficient reactions.

Scale-up upcycling of waste polyethylene terephthalate plastics to biodegradable polyglycolic acid plastics

Electrochemical upcycling of waste polyethylene terephthalate (PET) into biodegradable polyglycolic acid (PGA) is a promising solution to relieve plastic pollution. However, both the low current density and tedious separation process for target glycolic acid (GA) products in a flow electrolysis have hindered industrial-scale applications. Here, we show an interfacial acid-base microenvironment regulation strategy for the efficient oxidation of PET-derived ethylene glycol (EG) into GA using Pd-CoCr2O4 catalysts. Specifically, only a cell voltage of 1.25 V is needed to deliver a current density of ca. 290 mA cm-2. Moreover, a green separation method is developed to obtain high-purity GA (99%). 20 kg of waste PET is employed for the pilot plant test (stack electrolyzer: 324 cm2 × 5), which exhibits 93.0% GA selectivity at 280 mA cm-2 (current: 90.72 A) with a yield rate of 0.32 kg h-1. After polymerization, PGA yield can reach up to 87%, demonstrating the potential of this technique for large-scale PGA production from waste PET.

Modulating Adsorption Behavior by Single-site Pt on RuO2 for Efficient Electrosynthesis of Glycolic Acid from Plastic Wastes

Electrochemical upcycling of polyethylene terephthalate (PET) wastes into valuable glycolic acid (GA) is an ideal solution for resource utilization. However, simultaneously achieving high activity and selectivity remains challenging due to the over-oxidation and C-C cleavage during ethylene glycol (EG) oxidation in PET hydrolysate. Herein, we develop an atomically isolated Pt on RuO2 (Pt1/RuO2) catalyst composed of high-density Pt-Ru interfaces that ensure single-site adsorption of EG, enrich surface *OH coverage and weaken *CO-CH2OH intermediate adsorption, thereby synergistically promoting GA generation. Specifically, Pt1/RuO2 delivers a remarkable mass activity of 8.09 A/mgPt, as well as a high GA Faradaic efficiency (95.3 %) and selectivity (96.9 %). Under membrane electrode assembly conditions, Pt1/RuO2 realizes a stable electrolysis over 500 h at 6 A with a GA yield rate of 4.06 g h-1. In-depth theoretical and in situ spectroscopic investigations reveal the synergy between isolated Pt and oxophilic RuO2 plays a crucial role in high-efficiency EG-to-GA conversion. This study offers valuable insights for the rational design of advanced catalysts for GA synthesis from PET wastes via a single-site doped bimetallic strategy.

Effect of glycerol concentration on rate and product speciation for Ni and Au-based catalysts

In this paper, we investigate the glycerol electrooxidation reaction (GEOR) on Au and Ni catalysts, specifically the effect of glycerol concentration on electrochemical activity and product speciation for GEOR in an electrochemical flow cell system. With Au foil, cyclic voltammogram behavior shifted from hysteretic to near-linear by increasing the concentration of glycerol from 0.1 M to 1 M. As a result, glycerol electrooxidation increased up to 1.4 V vs. RHE with a higher glycerol concentration. The major products were formic acid and glycolic acid, yet minor products of value-added glyceric acid, lactic acid, and dihydroxyacetone were observed at a higher glycerol concentration. Competition between glycerol and the Au surface for hydroxide inhibits the formation of poisoning Au oxide (AuOx) species and enables the formation of low degree oxidation products. With Ni foil, the GEOR peak current density in cyclic voltammetry increased with glycerol concentration, however, formation of the major product, formic acid, decreased. This study examines and utilizes differences in GEOR mechanism on Ni vs. Au catalysts to vary product speciation in flow cell systems.

Electrooxidation of Ethylene Glycol to Glycolic Acid with Pt-Ni(OH)2 Catalysts: High Efficiency and Selectivity for PET Plastics Upgrading

The electroconversion of polyethylene terephthalate (PET) into C2 fine chemicals and hydrogen (H2) presents a promising solution for advancing the circular plastics economy. In this study, we report the electrooxidation of ethylene glycol (EG) to glycolic acid (GA) using a Pt-Ni(OH)2 catalyst, achieving a high Faraday efficiency (>90 %) even at high current densities (250 mA cm-2 at 0.8 V vs. RHE). Notably, this catalyst outperforms most existing Pt-based catalysts in terms of catalytic activity. Experimental analyses reveal that: 1) Ni(OH)2 enhances the adsorption of OH- ions and promotes the rapid generation of *OH active species, which are essential for the efficient oxidation of EG to GA; 2) the oxygenophilic nature of Pt improves EG adsorption, and in synergy with Ni, accelerates the oxidation process. Furthermore, Pt lowers the electrolysis potential, preventing excessive oxidation and ensuring high selectivity for GA. This work offers a promising pathway for the electrooxidation-based upgrading of PET plastics and provides valuable insights for future research in this area.

Nanoscale high-entropy surface engineering promotes selective glycerol electro-oxidation to glycerate at high current density

Selective production of valuable glycerol chemicals, such as glycerate (which serves as an important chemical intermediate), poses a significant challenge due to the facile cleavage of C-C bonds and the presence of multiple reaction pathways. This challenge is more severe in the electro-oxidation of glycerol, which requires the development of desirable electrocatalysts. To facilitate the glycerol electro-oxidation reaction to glycerate, here we present an approach utilizing a high-entropy PtCuCoNiMn nanosurface. It exhibits exceptional activity (~200 mA cm-2 at 0.75 V versus a reversible hydrogen electrode) and selectivity (75.2%). In situ vibrational measurements and theoretical calculations reveal that the exceptional glycerol electro-oxidation selectivity and activity can be attributed to the unique characteristics of the high-entropy surface, which effectively modifies the electronic structure of the exposed Pt sites. The catalyst is successfully applied in an electrolyser for long-term glycerol electro-oxidation reaction, demonstrating excellent performance (~200 mA cm-2 at 1.2Vcell) over 210 h. The present study highlights that tailoring the catalytic sites at the catalyst-electrolyte interface by constructing a high-entropy surface is an effective strategy for electrochemical catalysis.

Deciphering the Role of Second Metal in M-Ni (M = Fe, Ni, and Mn) Heterobimetallic Electrocatalysts in Controlling the HAT versus Hydride Transfer Mechanism for the Dehydrogenation of Alcohols

The second 3d-transition metal incorporation in Ni-(oxy)hydroxide has a drastic effect on alkaline OER and alcohol dehydrogenation reactivity. While Mn incorporation suppresses the alkaline OER, it greatly improves the alcohol dehydrogenation reactivity. A complete reversal of reactivity is obtained when Fe is incorporated, which shows better performance for alkaline OER with poor alcohol dehydrogenation reactivity. The role of the second 3d-metal is elusive due to the lack of systematic mechanistic studies. In this report, we thoroughly analyzed a series of M─Ni (M = Fe, Ni, Mn) (oxy)hydroxides derived from electrochemical activation of M-MOF grown on nickel foam for its electrochemical activity in alkaline OER and aliphatic, benzyl alcohol dehydrogenation. With the help of pH-dependence and kinetic isotope effect studies, the potential-determining step (PDS) and the rate-determining step (RDS) have been elucidated. The Hammett analysis revealed critical information about the transition state and offered insight into the hydrogen atom transfer (HAT) versus hydride transfer (HT) for alcohol dehydrogenation operative in various heterobimetallic electrocatalysts. Further, the superior alcohol dehydrogenation reactivity of NiMn catalyst for PET hydrolysate electro-oxidation is extended to afford valuable chemicals with concomitant production of hydrogen.

Photocatalytic Conversion of Polyester-Derived Alcohol into Value-Added Chemicals by Engineering Atomically Dispersed Pd Catalyst

Photoreforming presents a promising strategy for upcycling waste polyester-derived alcohol into valuable chemicals. However, it remains a great challenge due to its low performance and unsatisfactory selectivity toward high-value C2 products. Here, we report the highly efficient and selective conversion of ethylene glycol (EG, a monomer of polyethylene terephthalate (PET)) to glycolaldehyde using atomically dispersed Pd species supported on TiO2 catalyst. A glycolaldehyde production rate of 5072 μmol gcat -1 h-1 with a selectivity of 90.0 % and long-term durability can be achieved. Experimental and theoretical results show that Pd single atoms can enhance the photocatalytic activity by enriching the photogenerated holes, which are the dominant species for the selective oxidation of EG to glycolaldehyde. More importantly, the adsorption of EG molecules on the catalysts is significantly promoted, which is subsequently transformed into RO⋅ radicals, a crucial intermediate in producing glycolaldehyde. Additionally, Pd single atoms on TiO2 enable the reduction of the glycolaldehyde desorption barrier, thereby facilitating high selectivity and inhibiting further oxidation to C1 products. This work provides new insights into the photocatalytic conversion of polyester wastes by atomic engineering.

Role of Water in Green Carbon Science

Within the context of green chemistry, the concept of green carbon science emphasizes carbon balance and recycling to address the challenge of achieving carbon neutrality. The fundamental processes in this field are oxidation and reduction, which often involve simple molecules such as CO2, CO, CH4, CHx, and H2O. Water plays a critical role in nearly all oxidation-reduction processes, and thus, it is a central focus of research in green carbon science. Water can act as a direct source of dihydrogen in reduction reactions or participate in oxidation reactions, frequently involving O-O coupling to produce hydrogen peroxide or dioxygen. At the atomic level, this coupling involves the statistically unfavorable proximity of two atoms, requiring optimization through a catalytic process influenced by two types of factors, as described by the authors. Extrinsic factors are related to geometrical and electronic criteria associated with the catalytic metal, involving its d-orbitals (or bands in the case of zerovalent metals and electrodes). Intrinsic factors are related to the coupling of oxygen atoms via their p-orbitals. At the mesoscopic or microscopic scale, the reaction medium typically consists of mixtures of lipophilic and hydrophilic phases with water, which may exist under supercritical conditions or as suspensions of microdroplets. These reactions predominantly occur at phase interfaces. A comprehensive understanding of the phenomena across these scales could facilitate improvements and even lead to the development of novel conversion processes.

Electrocatalytic Ethylene Glycol to Long-Chain C3+ α-Hydroxycarboxylic Acids via Cross-Coupling with Primary Alcohols

Electrocatalytic conversion of ethylene glycol (EG) into α-hydroxycarboxylic acids (α-HCAs) holds great importance for advancing sustainable chemical development since EG is widely accessible in polyethylene terephthalate (PET) plastic and biomass. Herein, we report the direct electrocatalytic cross-coupling of EG and primary C1-C4 alcohol, producing carbon-chain-propagated C3-C6 α-HCAs over a gold (Au) catalyst. Taking EG and methanol (MeOH) cross-coupling to lactic acid (LA) as an example, experimental evidence shows that stabilization of the aldehyde intermediates (glycolaldehyde and formaldehyde from EG and MeOH, respectively) without overoxidation is important for the following cross-coupling via aldol condensation and thus LA formation. Based on this understanding, we systematically modulate the catalyst and reaction conditions, achieving a high LA productivity of 268.1 μmol cm-2 h-1 with a Faradaic efficiency of 28.7% at a constant current of 100 mA cm-2. The carbon-chain propagation strategy shows generality for EG cross-coupling with C1-C4 primary alcohols, successfully producing C3-C6 α-HCAs. As a proof of concept, a postconsumer PET bottle is converted to LA with a good productivity of 224.5 μmol cm-2 in a 2 h electrolysis. This work demonstrates the possibility of the electrocatalytic strategy to convert EG into long-chain compounds via C-C bond cross-coupling, representing a crucial step toward building a sustainable society.

State-of-the-art and perspectives of hydrogen generation from waste plastics

Waste plastic utilization and hydrogen production present significant economic and social challenges but also offer opportunities for research and innovation. This review provides a comprehensive analysis of the latest advancements and innovations in hydrogen generation coupled with waste plastic recycling. It explores various strategies, including pyrolysis, gasification, aqueous phase reforming, photoreforming, and electrocatalysis. Pyrolysis and gasification in combination with catalytic reforming or water gas-shift are currently the most feasible and scalable technologies for hydrogen generation from waste plastics, with pyrolysis operating in an oxygen-free environment and gasification in the presence of steam, though both require high energy inputs. Aqueous phase reforming operates at moderate temperatures and pressures, making it suitable for oxygenated plastics, but it faces challenges related to feedstock limitations, catalyst costs and deactivation. Photoreforming and electrocatalytic reforming are emerging, sustainable methods that use sunlight and electricity, respectively, to convert plastics into hydrogen. Still, they suffer from low efficiency, scalability issues, and limitations to specific plastic types like oxygenated polymers. The challenges and solutions to commercializing plastic-to-hydrogen technologies, drawing on global industrial case studies have been outlined. Maximizing hydrogen productivity and selectivity, minimizing energy consumption, and ensuring stable operation and scaleup of plastic recycling are crucial parameters for achieving commercial viability.

Stable Ni(II) sites in Prussian blue analogue for selective, ampere-level ethylene glycol electrooxidation

The industrial implementation of coupled electrochemical hydrogen production systems necessitates high power density and high product selectivity for economic viability and safety. However, for organic nucleophiles (e.g., methanol, urea, and amine) electrooxidation in the anode, most catalytic materials undergo unavoidable reconstruction to generate high-valent metal sites under harsh operation conditions, resulting in competition with oxygen evolution reaction. Here, we present unique Ni(II) sites in Prussian blue analogue (NiFe-sc-PBA) that serve as stable, efficient and selective active sites for ethylene glycol (EG) electrooxidation to formic acid, particularly at ampere-level current densities. Our in situ/operando characterizations demonstrate the robustness of Ni(II) sites during EG electrooxidation. Molecular dynamics simulations further illustrate that EG molecule tends to accumulate on the NiFe-sc-PBA surface, preventing hydroxyl-induced reconstruction in alkaline solutions. The stable Ni(II) sites in NiFe-sc-PBA anodes exhibit efficient and selective EG electrooxidation performance in a coupled electrochemical hydrogen production flow cell, producing high-value formic acid compared to traditional alkaline water splitting. The coupled system can continuously operate at stepwise ampere-level current densities (switchable 1.0 or 1.5 A cm-2) for over 500 hours without performance degradation.

Pulsed electrosynthesis of glycolic acid through polyethylene terephthalate upcycling over a mesoporous PdCu catalyst

Electrocatalytic upcycling of polyethylene terephthalate (PET) plastics offers a promising and sustainable route that not only addresses serious waste pollution but also produces high value-added chemicals. Despite some important achievements, their activity and selectivity have been slower than needed. In this work, pulsed electrocatalysis is employed to engineer chemisorption properties on a lamellar mesoporous PdCu (LM-PdCu) catalyst, which delivers high activity and stability for selective electrosynthesis of high value-added glycolic acid (GA) from PET upcycling under ambient conditions. LM-PdCu is synthesized by in situ nucleation and attachment strategy along assembled lamellar templates, whose stacked morphology and lamellar mesoporous structure kinetically accelerate selective desorption of GA and expose fresh active sites of metal catalysts for continuous electrocatalysis at pulsed mode. This strategy thus delivers GA Faraday efficiency of >92% in wide potential windows, yield rate of reaching 0.475 mmol cm-2 h-1, and cycling stability of exceeding 20 cycles for electrocatalytic PET upcycling. Moreover, pulsed electrocatalysis discloses good electrocatalytic performance for scaled-up GA electrosynthesis from real bottle waste plastics. This work presents a sustainable route for selective electrosynthesis of value-added chemicals through upcycling of various waste feedstocks.

Selective Electrooxidation of Crude Glycerol to Lactic Acid Coupled With Hydrogen Production at Industrially-Relevant Current Density

Transforming glycerol (GLY, biodiesel by-product) into lactic acid (LA, biodegradable polymer monomer) through sustainable electrocatalysis presents an effective strategy to reduce biodiesel production costs and consequently enhance its applications. However, current research faces a trade-off between achieving industrially-relevant current density (>300 mA cm-2) and high LA selectivity (>80%), limiting technological advancement. Herein, a Au3Ag1 alloy electrocatalyst is developed that demonstrates exceptional LA selectivity (85%) under high current density (>400 mA cm-2). The current density can further reach 1022 mA cm-2 at 1.2 V versus RHE, superior to most previous reports for GLY electrooxidation. It is revealed that the Au3Ag1 alloy can enhance GLY adsorption and reactive oxygen species (OH*) generation, thereby significantly boosting activity. As a proof of concept, a homemade flow electrolyzer is constructed, achieving remarkable LA productivity of 68.9 mmol h-1 at the anode, coupled with efficient H2 production of 3.5 L h-1 at the cathode. To further unveil the practical possibilities of this technology, crude GLY extracted from peanut oil into LA is successfully transformed, while simultaneously producing H2 at the cathode. This work showcases a sustainable method for converting biodiesel waste into high-value products and hydrogen fuel, promoting the broader application of biodiesel.

Circular Economy and Chemical Conversion for Polyester Wastes

Polyester waste in the environment threatens public health and environmental ecosystems. Chemical recycling of polyester waste offers a dual solution to ensure resource sustainability and ecological restoration. This minireview highlights the traditional recycling methods and novel recycling strategies of polyester plastics. The conventional strategy includes pyrolysis, carbonation, and solvolysis of polyesters for degradation and recycling. Furthermore, the review delves into exploring emerging technologies including hydrogenolysis, electrocatalysis, photothermal, photoreforming, and enzymatic for upcycling polyesters. It emphasizes the selectivity of products during the polyester conversion process and elucidates conversion pathways. More importantly, the separation and purification of the products, the life cycle assessment, and the economic analysis of the overall recycling process are essential for evaluating the environmental and economic viability of chemical recycling of waste polyester plastics. Finally, the review offers perspective into the future challenges and developments of chemical recycling in the polyester economy.

Incorporating Ordered Indium Sites into Rhodium for Ultra-Low Potential Electrocatalytic Conversion of Ethylene Glycol to Glycolic Acid

The upcycling of polyethylene terephthalate (PET)-derived ethylene glycol (EG) to glycolic acid (GA, a biodegradable polymer monomer) via electrocatalysis not only produces valuable chemicals but also mitigates plastic pollution. However, the current reports for electrooxidation of EG-to-GA usually operate at reaction potentials of >1.0 V vs reversible hydrogen electrode (RHE), much higher than the theoretical potential (0.065 V vs RHE), resulting in substantial energy wastage. Herein, body-centered cubic RhIn intermetallic compounds (IMCs) anchored on carbon support (denoted as RhIn/C) are synthesized, which shows excellent performance for the EG-to-GA with an onset potential of only 0.35 V vs RHE, lower than the values reported in current literature. The catalyst also possesses satisfactory GA selectivity (85% at 0.65 V vs RHE). Experimental results combined with density functional theory calculations demonstrate that RhIn IMCs enhance the adsorption of EG and OH-, facilitating the generation of reactive oxygen species and thereby improving catalytic performance. RhIn/C also exhibits excellent electrocatalytic performance for hydrogen evolution reaction, ensuring that it can be used as a bifunctional catalyst in the two-electrode system for EG electrooxidation coupled with hydrogen production. This work opens new avenues for reducing the energy consumption of electrocatalytic upcycling of PET-derived EG and clean energy production.

CeO2 Modification Promotes the Oxidation Kinetics for Adipic Acid Electrosynthesis from KA Oil Oxidation at 200 mA cm-2

Electrocatalytic oxidation of cyclohexanol/cyclohexanone in water provides a promising strategy for obtaining adipic acid (AA), which is an essential feedstock in the polymer industry. However, this process is impeded by slow kinetics and limited Faradaic efficiency (FE) due to a poor understanding of the reaction mechanism. Herein, NiCo2O4/CeO2 is developed to enable the electrooxidation of cyclohexanol to AA with a 0.0992 mmol  h-1 cm-2 yield rate and 87 % Faradaic efficiency at a lower potential. Mechanistic investigations demonstrate that cyclohexanol electrooxidation to AA is a gradual oxidation process involving the dehydrogenation of cyclohexanol to cyclohexanone, the generation of 2-hydroxy cyclohexanone, and subsequent C-C cleavage. Theoretical calculations reveal that electronic interactions between CeO2 and NiCo2O4 decrease the energy barrier of cyclohexanone oxidation to 2-hydroxy cyclohexanone and inhibit the *OH to *O step, leading to AA electrosynthesis with a high yield rate and FE. Kinetic analysis further elucidates the effect of CeO2 on promoting cyclohexanone adsorption and activation on the electrode surface, thus facilitating the reaction kinetics. Moreover, a two-electrode flow reactor is constructed to produce 72.1 mmol AA and 10.4 L H2 by using KA oil as the anode feedstock at 2.5 A (200 mA cm-2), demonstrating promising potential.

Surface Coverage Tuning for Suppressing Over-Oxidation: A Case of Photoelectrochemical Alcohol-to-Aldehyde/Ketone Conversion

Suppressing over-oxidation is a crucial challenge for various chemical intermediate synthesis in heterogeneous catalysis. The distribution of oxidative species and the substrate coverage, governed by the direction of electron transfer, are believed to influence the oxidation extent. In this study, we presented an experimental realization of surface coverage modulation on a photoelectrode using a photo-induced charge activation method. Through the surface coverage modulation, both pre-oxidized alcohol substrates and surface coverage were increased, which not only improved the reaction kinetics but also suppressed the over-oxidation of the generated aldehydes/ketones. As a demonstration, the Faradaic efficiency for the conversion of glycerol to dihydroxyacetone increased from 31.8 % to 46.8 % (with selectivity rising from 47.6 % to 71.3 %), from 73.4 % to 87.8 % for benzyl alcohol to benzyl aldehyde (selectivity increasing from 76.7 % to 92.4 %) and from 4.2 % to 53.6 % for ethylene glycol to glycolaldehyde (selectivity increasing from 6.2 % to 62.7 %). Our findings offer a promising strategy for the production of high-value carbon products in heterogeneous catalysis.

Vacancy-rich NiFe-LDH/carbon paper as a novel self-supporting electrode for the electro-Fenton degradation of polyvinyl chloride microplastics

Electrochemically upcycling polyvinyl chloride (PVC) into high-value small molecules represents a sustainable strategy for mitigating plastic pollution. Herein, a cost-effective self-supporting electrode with abundant vacancies, i.e., NiFe-layered double hydroxide nanoarrays in-situ grown on the surface of carbon paper (denoted as NiFeV-LDH/CP), is developed for the electro-Fenton degradation of PVC microplastics (MPs). The NiFeV-LDH catalyst shows a high selectivity of 76 % towards H2O2 production via two-electron oxygen reduction reaction (2e- ORR). Density functional theory (DFT) calculations reveal that the energy barrier of rate-determining step (*H2O2 desorption) decreases over the vacancy-enriched NiFeV-LDH related to the pristine NiFeZn-LDH. The influence of vacancy concentration, reaction temperature and initial concentration of PVC MPs were systematically investigated. Under optimized conditions, the NiFeV-LDH/CP electrode exhibits an outstanding degradation performance of PVC MPs via direct cathodic reduction and oxidation by hydroxyl radicals. This work demonstrates that the electro-Fenton technology using LDH-based self-supporting electrodes is a promising and environmentally-friendly approach for waste plastic treatment.

Electrocatalytic Biomass Oxidation via Acid-Induced In Situ Surface Reconstruction of Multivalent State Coexistence in Metal Foams

Electrocatalytic biomass conversion offers a sustainable route for producing organic chemicals, with electrode design being critical to determining reaction rate and selectivity. Herein, a prediction-synthesis-validation approach is developed to obtain electrodes for precise biomass conversion, where the coexistence of multiple metal valence states leads to excellent electrocatalytic performance due to the activated redox cycle. This promising integrated foam electrode is developed via acid-induced surface reconstruction to in situ generate highly active metal (oxy)hydroxide or oxide (MOxHy or MOx) species on inert foam electrodes, facilitating the electrooxidation of 5-hydroxymethylfurfural (5-HMF) to 2,5-furandicarboxylic acid (FDCA). Taking nickel foam electrode as an example, the resulting NiOxHy/Ni catalyst, featuring the coexistence of multivalent states of Ni, exhibits remarkable activity and stability with a FDCA yields over 95% and a Faradaic efficiency of 99%. In situ Raman spectroscopy and theoretical analysis reveal an Ni(OH)2/NiOOH-mediated indirect pathway, with the chemical oxidation of 5-HMF as the rate-limiting step. Furthermore, this in situ surface reconstruction approach can be extended to various metal foams (Fe, Cu, FeNi, and NiMo), offering a mild, scalable, and cost-effective method for preparing potent foam catalysts. This approach promotes a circular economy by enabling more efficient biomass conversion processes, providing a versatile and impactful tool in the field of sustainable catalysis.

A Coherent-Lattice Atomic-Level Heterojunction Enabling Efficient and Selective Upcycling of Glycerol for Lactic Acid and H2 Production

Photocatalytic upcycling of glycerol, a significant byproduct of biodiesel, to value-added lactic acid coupled with H2 production shows great promise for resource utilization and renewable fuel production. However, this reaction is currently limited to low efficiency and moderate selectivity due to insufficient light absorption, rapid charge carrier recombination, and unfavorable reaction kinetics. Herein, we report an atomic-level heterojunction photocatalyst consisting of CdxZn1-xS embedded uniformly with Cu-S3 moieties at the atomic-level scale. Due to the formation of a coherent-lattice interface with strong interfacial electronic interactions between Cu-S3 moieties and the CdxZn1-xS host, as well as the significant localized surface plasmon resonance effects induced by Cu-S3 moieties, such a photocatalyst shows much enhanced charge separation and transfer efficiency and strong light absorption covering the full solar-light spectrum. As a result, a 10-fold increase in glycerol conversion to lactic acid (LA) coupled with H2 production is achieved, with the selectivity of LA reaching over 95%. The present work demonstrates the potential of photocatalysis for biomass upcycling toward the coproduction of valuable chemicals and H2 fuel using structure-defined photocatalysts.

Ordered Pt3Mn Intermetallic Setting the Maximum Threshold Activity of Disordered Variants for Glycerol Electrolysis

Glycerol electrolysis is a promising strategy for generating hydrogen at the cathode and value-added products at the anode. However, the effect of the atomic distribution within catalysts on their catalytic performance remains largely unexplored, primarily because of the inherent complexity of the glycerol oxidation reaction (GOR). Herein, an ordered Pt3Mn (O-Pt3Mn) intermetallic compound and a disordered Pt3Mn (D-Pt3Mn) alloy are used as model catalysts, and their performance in the GOR and hydrogen evolution reaction (HER) is studied. O-Pt3Mn consistently outperforms D-Pt3Mn and commercial Pt/C catalysts. It can generate high-value glycerate at a notable production rate of 17 mM h-1 while achieving an impressively low cell voltage of 0.76 V for glycerol electrolysis, which is ∼0.98 V lower than that required for water electrolysis. Statistical analysis using theoretical calculations reveals that Pt-Pt-Pt hollow sites are crucial for the catalytic GOR and HER. The averaged adsorption energies of key intermediates (simplified as C*, O*, and H*) on diverse catalysts closely correlate with their experimentally observed activity. Our proposed linear models accurately predict these adsorption energies, exhibiting high correlation coefficients ranging from 0.97 to 0.99 and highlighting the significance of the distribution of the topmost and subsurface-corner Mn atoms in determining these adsorption energies. By sampling all possible Mn configurations within the fitted linear models, we confirm that O-Pt3Mn establishes the maximum activity threshold for the GOR and HER compared with any disordered variant. This study presents an innovative framework for exploring the effect of the atomic distribution within catalysts on their catalytic performance and designing high-performance catalysts for complex reactions.

Promoting Alcohols Electrooxidation Coupled with Hydrogen Production via Asymmetric Pulse Potential Strategy

Electrocatalytic organic oxidation coupled with hydrogen (H2) production emerges as a profitable solution to simultaneously reduce overall energy consumption of H2 production and synthetic high-value chemicals. Noble metal catalysts are highly efficient electrocatalysts in oxidation reactions, but they deactivate easily weakening the benefit in actual production. Herein, we report a universal asymmetric pulse potential strategy to achieve long-term stable operation of noble metals for various alcohol oxidation reactions and noble metal catalysts. For example, by pulsed potentials between 0.8 V and 0 V vs. RHE, palladium (Pd)-catalyzed glycerol (GLY) electrooxidation can continuously proceed for more than 2800 h with glyceric acid (GLA) selectivity of >70 %. Whereas, Pd electrocatalyst becomes nearly deactivated within 6 h of reaction under conventional potentiostatic strategy. Experimental and theoretical calculation results reveal that the generated electrophilic OH* from H2O/OH- oxidation on Pd (denoted as Pd-OH*) acts as main active species for GLY oxidation. However, Pd-OH* is prone to be oxidized to PdOx resulting in performance decay. When a short reduction potential (e.g., 0 V vs. RHE for 5 s) is powered, PdOx can be reversibly reduced to restore the current. Moreover, we tested the feasibility of this strategy in a flow electrolyzer, verifying the practical application potential.

Accelerated Selective Electrooxidation of Ethylene Glycol and Inhibition of C-C Dissociation Facilitated by Surficial Oxidation on Hollowed PtAg Nanostructures via In Situ Dynamic Evolution

Electro-upgrading of low-cost alcohols such as ethylene glycol is a promising and sustainable approach for the production of value-added chemicals while substituting energy-consuming OER in water splitting. However, the sluggish kinetics and possibility of C-C dissociation make the design of selective and efficient electrocatalysts challenging. Herein, we demonstrate the synthesis of a hollowed bimetallic PtAg nanostructure through an in situ dynamic evolution method that could efficiently drive the selective electrochemical ethylene glycol oxidation reaction (EGOR). The resulting mild surficial oxidation has intrinsically improved EGOR activity, exhibiting a remarkable performance toward glycolate (selectivity up to 99.2% and faradic efficiency ∼97%) at high current density with low overpotential (355 mA·cm-2 at 1.0 V, 16.3 A·mgPt -1), exceeding prior outcomes. Through comprehensive operando characterization and theoretical calculations, this study systematically reveals that the in situ formation of Pt-O(H)ad is pivotal for modulating the electronic structure of surface and facilitating the selective electrooxidation and adsorption of -CH2OH. The competitive C-C dissociation pathway toward HCOO- is concurrently inhibited in comparison to Pt. An industrial-level current coupled with hydrogen production at low cell voltages was also achieved. These findings offer more in-depth mechanistic understanding of the EGOR's reaction pathway mediated by surface environment in Pt-based electrocatalysts.

Hydrogenating Polyethylene Terephthalate into Degradable Polyesters

The recycling and upcycling of polyethylene terephthalate (PET), the most widely used polyester plastic globally, has attracted growing attention concerning its disposal as non-degradable waste in the natural environment. Transforming end-of-life PET into (bio)degradable polyester offers a novel approach to managing its waste. In this study, we introduce a simple process capable of converting waste PET into degradable polyester, polyethylene terephthalate-polyethylene-1,4-cyclohexanedicarboxylate (PET-PECHD), by partly hydrogenating the aromatic rings (x) into aliphatic ones (y). The polyesters with variable x/y compositions ranging from 100/0 to 0/100 can be achieved, and the molecular weight (Mw) can be maintained when x/y >87/13 due to the nonobvious depolymerization. Pronounced depolymerization would occur with deeper hydrogenation, which generates a blend of PET-PECHD and polyethylene-1,4-cyclohexanedicarboxylate (PECHD) with lower Mw, and finally a single-type polymer PECHD. The PET-PECHD demonstrates comparable thermal stability and mechanical strength compared to PET, along with superior extensibility, barrier properties, and (bio)degradability in acidic, alkaline solutions, and moist soil. This research highlights the potential for cost-effective, large-scale production of degradable polyester from real-life plastic waste.

Anti-poisoning of CO and carbonyl species over Pd catalysts during the electrooxidation of ethylene glycol to glycolic acid at elevated current density

The electrocatalytic oxidation of ethylene glycol (EG) to produce valuable glycolic acid (GLYA) is a promising strategy to tackle EG overcapacity. Despite the good selectivity of Pd for EG oxidation, its performance is constrained by limited mass activity and toxicity of intermediates like CO or CO-analogues. This study reports the alloying of Pd with Ni and Mo metals to enhance the activity and durability of EG oxidation in alkaline media. Notably, the peak current density reached up to 2423 mA mg-1, double that of pristine Pd/C, accompanied by a GLYA Faraday efficiency up to 87.7%. Moreover, PdNiMo/C exhibited a 5-fold slower activity decline compared to Pd/C. In situ experiments and theoretical analysis reveal that Ni and Mo synergistically strengthen the oxygen affinity of the catalyst, facilitating the generation of *OH radicals at lower potentials, thereby accelerating EG oxidation kinetics. Additionally, Ni incorporation prevents C-C bond cleavage and weakens CO adsorption, effectively mitigating catalyst poisoning.

Upcycling Polyethylene to High-Purity Hydrogen under Ambient Conditions via Mechanocatalysis

Polyethylene (PE) is the most abundant plastic waste, and its conversion to hydrogen (H2) offers a promising route for clean energy generation. However, PE decomposition typically requires high temperatures due to its strong chemical bonds, leading to significant carbon emissions and low H2 selectivity (theoretically less than 75 vol % after accounting for further steam-reforming reactions). Here, we report a mechanocatalytic strategy that upcycles PE into high-purity H2 (99.4 vol %) with an exceptional H2 recovery ratio of 98.5 % (versus 15.7 % via thermocatalysis), using manganese as a catalyst at a low temperature of 45 °C. This method achieves a reaction rate 3 orders of magnitude higher than thermocatalysis. The marked improvement in H2 recovery ratio is mainly due to metal carbides formation induced by the mechanocatalytic process, which does not catalyze hydrocarbons formation. This work is expected to advance studies of the conversion of polyolefins to high-purity H2 with net-zero carbon emissions.

Cation-Vacancy Engineering in Cobalt Selenide Boosts Electrocatalytic Upcycling of Polyester Thermoplastics at Industrial-Level Current Density

The past decades have witnessed the increasing accumulation of plastics, posing a daunting environmental crisis. Among various solutions, converting plastics into value-added products presents a significant endeavor. Here, an electrocatalytic upcycling route that efficiently converts waste poly(butylene terephthalate) plastics into high-value succinic acid with high Faradaic efficiency of 94.0% over cation vacancies-rich cobalt selenide catalyst is reported, showcasing unprecedented activity (1.477 V vs. RHE) to achieve an industrial-level current density of 1.5 A cm-2, and featuring a robust operating durability (≈170 h). In particular, when combining butane-1,4-diol monomer oxidation (BOR) with hydrogen evolution using the cation vacancy-engineered cobalt selenide as bifunctional catalyst, a relatively low cell voltage of 1.681 V is required to reach 400 mA cm-2, manifesting an energy-saving efficiency of ≈15% compared to pure water splitting. The mechanism and reaction pathways of BOR over the vacancies-rich catalyst are first revealed through theoretical calculations and in-situ spectroscopic investigations. The generality of this catalyst is evidenced by its powerful electrocatalytic activity to other polyester thermoplastics such as poly(butylene succinate) and poly(ethylene terephthalate). These electrocatalytic upcycling strategies can be coupled with the reduction of small molecules (e.g., H2O, CO2, and NO3 -), shedding light on energy-saving production of value-added chemicals.

A perspective on field-effect in energy and environmental catalysis

The development of catalytic technologies for sustainable energy conversion is a critical step toward addressing fossil fuel depletion and associated environmental challenges. High-efficiency catalysts are fundamental to advancing these technologies. Recently, field-effect facilitated catalytic processes have emerged as a promising approach in energy and environmental applications, including water splitting, CO2 reduction, nitrogen reduction, organic electrosynthesis, and biomass recycling. Field-effect catalysis offers multiple advantages, such as enhancing localized reactant concentration, facilitating mass transfer, improving reactant adsorption, modifying electronic excitation and work functions, and enabling efficient charge transfer and separation. This review begins by defining and classifying field effects in catalysis, followed by an in-depth discussion on their roles and potential to guide further exploration of field-effect catalysis. To elucidate the theory-structure-activity relationship, we explore corresponding reaction mechanisms, modification strategies, and catalytic properties, highlighting their relevance to sustainable energy and environmental catalysis applications. Lastly, we offer perspectives on potential challenges that field-effect catalysis may face, aiming to provide a comprehensive understanding and future direction for this emerging area.

Mineralizing Biofilm towards Sustainable Conversion of Plastic Wastes to Hydrogen

The integration of inorganic materials with biological machinery to convert plastics into fuels offers a promising strategy to alleviate environmental pollution and energy crisis. Herein, we develop a type of hybrid living material via biomineralization of CdS onto Shewanella oneidensis-based biofilm, which is capable of sustainable hydrogen production from poly(lactic acid) (PLA) wastes under daylight. We reveal that the formed biofilm microstructure provides an independent anaerobic microenvironment that simultaneously supports cellular viability, maintains hydrogenase activity, and preserves the functional stability of CdS, giving rise to the efficient plastic-to-hydrogen conversion efficiency as high as 3751 μmol H2 g-1 PLA. Besides, by genetically engineering transmembrane pili conduit and incorporating conductive nanomaterials to strengthen the electron transfer across cellular interface and biofilm matrices, we show that the conversion efficiency is further enhanced to 5862 μmol H2 g-1 PLA. Significantly, we exhibit that a long-term sustainable plastic-to-hydrogen conversion of 63 d could be achieved by periodically replenishing PLA wastes. Overall, by the synergistic integration of biotic-abiotic characteristics the developed biofilm-based biomineralized hybrid living material is anticipated to provide a new platform toward the efficient conversion of plastic wastes into valuable fuels, and bridge the gap between environmental contamination and green energy production.

Pt/IrOx enables selective electrochemical C-H chlorination at high current

Employing electrochemistry for the selective functionalization of liquid alkanes allows for sustainable and efficient production of high-value chemicals. However, the large potentials required for C(sp3)-H bond functionalization and low water solubility of such alkanes make it challenging. Here we discover that a Pt/IrOx electrocatalyst with optimized Cl binding energy enables selective generation of Cl free radicals for C-H chlorination of alkanes. For instance, we achieve monochlorination of cyclohexane with a current up to 5 A, Faradaic efficiency (FE) up to 95% and stable performance over 100 h in aqueous KCl electrolyte. We further demonstrate that our system can directly utilize concentrated seawater derived from a solar evaporation reverse osmosis process, achieving a FE of 93.8% towards chlorocyclohexane at a current of 1 A. By coupling to a photovoltaic module, we showcase solar-driven production of chlorocyclohexane using concentrated seawater in a membrane electrode assembly cell without any external bias. Our findings constitute a sustainable pathway towards renewable energy driven chemicals manufacture using abundant feedstock at industrially relevant rates.

Synergistic enhancement of electrochemical alcohol oxidation by combining NiV-layered double hydroxide with an aminoxyl radical

Electrochemical alcohol oxidation (EAO) represents an effective method for the production of high-value carbonyl products. However, its industrial viability is hindered by suboptimal efficiency stemming from low reaction rates. Here, we present a synergistic electrocatalysis approach that integrates an active electrode and aminoxyl radical to enhance the performance of EAO. The optimal aminoxyl radical (4-acetamido-2,2,6,6-tetramethylpiperidine 1-oxyl) and Ni0.67V0.33-layered double hydroxide (LDH) are screen as cooperative electrocatalysts by integrating theoretical predictions and experiments. The Ni0.67V0.33-LDH facilitates the adsorption and activation of N-(1-hydroxy-2,2,6,6-tetramethylpiperidin-4-yl)acetamide (ACTH) via interactions with ketonic oxygen, thereby improving selectivity and yield at high current densities. The electrolysis process is scaled up to produce 200 g of the steroid carbonyl product 8b (19-Aldoandrostenedione), achieving a yield of 91% and a productivity of 243 g h-1. These results represent a promising method for accelerating electron transfer to enhance alcohol oxidation, highlighting its potential for practical electrosynthesis applications.

Evaluation of Active Oxygen Species Derived from Water Splitting for Electrocatalytic Organic Oxidation

Active oxygen species (OH*/O*) derived from water electrolysis are essential for the electrooxidation of organic compounds into high-value chemicals, which can determine activity and selectivity, whereas the relationship between them remains unclear. Herein, using glycerol (GLY) electrooxidation as a model reaction, we systematically investigated the relationship between GLY oxidation activity and the formation energy of OH* (ΔGOH*). We first identified that OH* on Au demonstrates the highest activity for GLY electrooxidation among various pure metals, based on experiments and density functional theory, and revealed that ΔGOH* on Au-based alloys is influenced by the metallic composition of OH* coordination sites. Moreover, we observed a linear correlation between the adsorption energy of GLY (Eads) and the d-band center of Au-based alloys. Comprehensive microkinetic analysis further reveals a volcano relationship between GLY oxidation activity, the ΔGOH* and the adsorption free energy of GLY (ΔGads). Notably, Au3Pd and Au3Ag alloys, positioned near the peak of the volcano plot, show excellent activity, attributed to their moderate ΔGOH* and ΔGads, striking a balance that is neither too high nor too low. This research provides theoretical insights into modulating active oxygen species from water electrolysis to enhance organic electrooxidation reactions.

Catalytic oxidation upcycling of polyethylene terephthalate to commodity carboxylic acids

Catalytic upcycling of polyethylene terephthalate (PET) into high-value oxygenated products is a fascinating process, yet it remains challenging. Here, we present a one-step tandem strategy to realize the thermal catalytic oxidation upcycling of PET to terephthalic acid (TPA) and high-value glycolic acid (GA) instead of ethylene glycol (EG). By using the Au/NiO with rich oxygen vacancies as catalyst, we successfully accelerate the hydrolysis of PET, accompanied by obtaining 99% TPA yield and 87.6% GA yield. The results reveal that the oxygen vacancies in NiO (NiO-Ov) support tend to adsorb hydrolysis product TPA, preferentially ensuring the strong adsorption of EG at the Au-NiO interface. Moreover, during the EG oxidation process, the Au-NiO interface, composed of two types of structures, quasi "AuNi alloy" and NiO-Ov, simultaneously promote the C-H bond activation, where Ni in "AuNi alloy" exhibits an oxytropism effect to anchor the C = O bond of the intermediate, while the residual O in NiO-Ov pillages the H in the C-H bond. Such Au/NiO catalyst is further extended to promote the thermal catalytic oxidation upcycling of other polyethylene glycol esters to GA with excellent catalytic performance.

Electroreforming of plastic wastes for value-added products

The problem of plastic pollution is becoming increasingly serious, and there is an urgent need to reduce the use of plastics and to improve the recovery rate of plastic wastes. Plastic wastes can be transformed into value-added chemicals at the anode through electrocatalytic conversion, while coupling with cathodic reduction reactions to achieve cogeneration of valuable anodic and cathodic products. The plastic electroreforming technology has unprecedented advantages, including a green and decentralizable process, renewable energy storage, ecological benefits, resource recovery, cost-effectiveness, and so on. Herein, we present a mini review about recent advances in this topic. We first discuss the electrooxidation mechanisms of different plastic wastes (such as polylactic acid, polyethylene glycol terephthalate, polyethylene, polyethylene furanoate, polybutylene terephthalate, and polyamides). Then, the progress of plastic waste-assisted electrolysis systems is summarized, including plastic waste-assisted water splitting for hydrogen production and oxygen reduction, as well as plastic electroreforming coupled with CO2 reduction, and the nitrate reduction reaction. Finally, the development prospects and challenges in this field are introduced and discussed. This review aims to provide a concise overview of the emerging plastic electroreforming, thus offering insight on the design of efficient and stable plastic-assisted electrolysis systems.

Surface Selenium Coating Promotes Selective Methanol-to-Formate Electrooxidation on Ni3Se4 Nanoparticles

In the quest to replace fossil fuels and reduce carbon dioxide emissions, developing energy technologies based on clean catalytic processes is fundamental. However, the cost-effectiveness of these technologies strongly relies on the availability of efficient catalysts made of abundant elements. Herein, this study presents a one-step hydrothermal method to obtain a series of Ni3Se4 nanoparticles with a layer of amorphous selenium on their surface. When employed as electrocatalysts for the methanol oxidation reaction (MOR), the optimized proper surface Se-coated Ni3Se4 nanoparticles exhibit a high current density of 160 mA cm-2 at 1.6 V, achieving a high methanol-to-formate Faradaic efficiency above 97.8% and excellent stability with less than 20% current decay after an 18 h chronoamperometry test. This excellent performance is rationalized using density functional theory calculations, which unveil that the electrochemical recombination of SeOx results in a reduction of the energy barrier for the dehydrogenation of methanol during the MOR process.

Plasma-Constructed Co2P-Ni2P Heterointerface for Electro‑Upcycling of Polyethylene Terephthalate Plastic to Co-Produce Hydrogen and Formate

Integrating electrochemical upcycling of polyethylene-terephthalate (PET) and the hydrogen evolution reaction (HER) is an energy-saving approach for electrolytic hydrogen (H2) production, along with the coproduction of formate. Herein, a novel and rapid strategy of cold plasma phosphating is employed to synthesize Co2P-Ni2P heterointerface decorated on carbon cloth (Co2P-Ni2P/CC) to catalyze H2 generation and reform PET. Notably, the obtained Co2P-Ni2P/CC exhibits eminent ethylene glycol oxidation reaction (EGOR) and HER activities, effectuating low potentials of merely 1.300 and -0.112 V versus RHE at 100 mA cm-2 for the EGOR and HER, respectively, also attaining an ultralow cell bias of 1.300 V at 10 mA cm-2 for EG oxidation assisted-water splitting. DFT and characterization results validate that the as-formed built-in electric fields in the Co2P-Ni2P heterointerface can accelerate electrons transfer and deepen structural self-reconstruction, thereby boosting effectively water dissociation and ethylene glycol (EG) dehydrogenation. Impressively, coupling HER with PET-derived EG-to-formate in a flow-cell electrolyzer assembled with Co2P-Ni2P/CC pair achieves an intriguing formate Faradaic efficiency of 90.6% and an extraordinary stable operation of over 70 h at 100 mA cm-2. The work exemplifies a facile and effective strategy for synthesizing metal phosphides electrocatalysts with extraordinary performance toward H2 generation of water splitting and recycling of PET.

Manipulating C-C coupling pathway in electrochemical CO2 reduction for selective ethylene and ethanol production over single-atom alloy catalyst

Manipulation C-C coupling pathway is of great importance for selective CO2 electroreduction but remain challenging. Herein, two model Cu-based catalysts, by modifying Cu nanowires with Ag nanoparticles (AgCu NW) and Ag single atoms (Ag1Cu NW), respectively, are rationally designed for exploring the C-C coupling mechanisms in electrochemical CO2 reduction reaction (CO2RR). Compared to AgCu NW, the Ag1Cu NW exhibits a more than 10-fold increase of C2 selectivity in CO2 reduction to ethanol, with ethanol-to-ethylene ratio increased from 0.41 over AgCu NW to 4.26 over Ag1Cu NW. Via a variety of operando/in-situ techniques and theoretical calculation, the enhanced ethanol selectivity over Ag1Cu NW is attributed to the promoted H2O dissociation over the atomically dispersed Ag sites, which effectively accelerated *CO hydrogenation to form *CHO intermediate and facilitated asymmetric *CO-*CHO coupling over paired Cu atoms adjacent to single Ag atoms. Results of this work provide deep insight into the C-C coupling pathways towards target C2+ product and shed light on the rational design of efficient CO2RR catalysts with paired active sites.

Mn and Mo co-doped NiS nanosheets induce abundant Ni3+-O bonds for efficient electro-oxidation of biomass

MnMo-NiS were synthesized for electro-oxidizing ethylene glycol (EG), glycerol (GLY), and 5-hydroxymethylfurfural (HMF), achieving faradaic efficiencies of 97.5%, 98.6%, and 99.2%, and yield rates of 615.7, 475.5, and 333.9 μmol h-1 cm-2. In situ Raman spectroscopy and multi-step chronoamperometry reveal that Ni3+-O is the active site.

Energy-Saving Ambient Electrosynthesis of Nylon-6 Precursor Coupled with Electrocatalytic Upcycling of Polyethylene Terephthalate

Cyclohexanone oxime is an important intermediate in the chemical industry, especially for the manufacture of nylon-6. The traditional cyclohexanone oxime production strongly relies on cyclohexanone-hydroxylamine and cyclohexanone ammoxidation processes, which require harsh reaction conditions and consume considerable amounts of energy. Herein, direct electrosynthesis of cyclohexanone oxime is reported from environmental pollutants nitrite and cyclohexanone with almost 100% yield by using low-cost Cu2Se nanosheets as electrocatalysts. Combination of in situ Fourier transform infrared spectroscopy and theoretical calculations verifies that the p-d orbital hybridization between Cu and Se elements could synergistically optimize the surface electronic structure and enable improved adsorption and formation of the key active N intermediate NH2OH*, thereby enhancing cyclohexanone/nitrite-to-cyclohexanone oxime conversion over the Cu2Se nanosheets. Based on these, an efficient asymmetric co-electrolysis system is further demonstrated by coupling cyclohexanone/nitrite-to-cyclohexanone oxime conversion with the upcycling of polyethylene terephthalate plastics, achieveing energy-saving simultaneously production of value-added products (cyclohexanone oxime and glycolic acid).

Electrocatalytic Valorization of Nitrate and Polyester Plastic for Simultaneous Production of Ammonia and Glycolic Acid

Electrochemical upcycling of nitrate and polyester plastic into valuable products is an ideal solution to realize the resource utilization. Here, the co-production of ammonia (NH3) and glycolic acid (GA) via electrochemical upcycling of nitrate and polyethylene terephthalate (PET) plastics over mesoporous Pd3Au film on Ni foam (mPd3Au/NF), which is synthesized by micelle-assisted replacement method, is proposed. The mPd3Au/NF with well-developed mesoporous structure provides abundant active sites and facilitated transfer channels and strong electronic effect. As such, the mPd3Au/NF exhibits high Faraday efficiencies of 97.28% and 95.32% at 0.9 V for the formation of NH3 and GA, respectively. Theoretical results indicate that the synergistic effect of Pd and Au can optimize adsorption energy of key intermediates *NOH and *OCH2-CH2OH on active sites and increase bond energy of C─C band, thereby improving the activity and selectivity for the formation of NH3 and GA. This work proposes a promising strategy for the simultaneous conversation of nitrate and PET plastic into high-value NH3 and GA.

Unraveling the Impact of Oxygen Vacancy on Electrochemical Valorization of Polyester Over Spinel Oxides

Electrochemical upcycling of end-of-life polyethylene terephthalate (PET) using renewable electricity offers a route to generate valuable chemicals while processing plastic wastes. However, it remains a huge challenge to design an electrocatalyst with reliable structure-property relationships for PET valorization. Herein, spinel Co3O4 with rich oxygen vacancies for improved activity toward formic acid (FA) production from PET hydrolysate is reported. Experimental investigations combined with theoretical calculations reveal that incorporation of VO into Co3O4 not only promotes the generation of reactive hydroxyl species (OH*) species at adjacent tetrahedral Co2+ (Co2+ Td), but also induces an electronic structure transition from octahedral Co3+ (Co3+ Oh) to octahedral Co2+ (Co2+ Oh), which typically functions as highly-active catalytic sites for ethylene glycol (EG) chemisorption. Moreover, the enlarged Co-O covalency induced by VO facilitates the electron transfer from EG* to OH* via Co2+ Oh-O-Co2+ Td interaction and the following C─C bond cleavage via direct oxidation with a glyoxal intermediate pathway. As a result, the VO-Co3O4 catalyst exhibits a high half-cell activity for EG oxidation, with a Faradaic efficiency (91%) and productivity (1.02 mmol cm-2 h-1) of FA. Lastly, it is demonstrated that hundred gram-scale formate crystals can be produced from the real-world PET bottles via two-electrode electroreforming, with a yield of 82%.

Enhanced hydroxyl adsorption and improved glycerol adsorption configuration for efficient glyceric acid production

Challenges such as insufficient reactivity and low selectivity of single C3 product limit the application of glycerol oxidation reaction (GOR) into the production of value-added products. In this work, Pd nanoparticles were loaded on supports containing different cations (NiFe(OH)2, NiCo(OH)2, and Ni(OH)2) using electrodeposition method. This approach facilitated the interactions between the Pd and the support, allowing for the regulation of the electronic structure and the design of catalyst morphology, ultimately leading to enhanced performance. Remarkably, Pd/NiCo(OH)2 displays improved activity (128.8 mA·cm-2 at 0.95 V vs. RHE), glyceric acid (GLA) selectivity (67 %) reaction kinetics and stability compared to pure Pd. Combined density functional theory (DFT) calculation and experimental results indicated that the superior electrocatalytic performance of Pd/NiCo(OH)2 arises from a lower d-band center, a unique nanorod array microstructure, high OHads coverage, an improved adsorption configuration for glycerol, and strong adsorption of glycerol and hydroxyl at the metal-support interface. This research presents a novel strategy for optimizing glycerol oxidation performance.

Membrane-Free Electrocatalytic Co-Conversions of PBS Waste Plastics and Maleic Acid into High-Purity Succinic Acid Solid

Plastic pollution, an increasingly serious global problem, can be addressed through the full lifecycle management of plastics, including plastics recycling as one of the most promising approaches. System design, catalyst development, and product separation are the keys in improving the economics of electrocatalytic plastics recycling. Here, a membrane-free co-production system was devised to produce succinic acid (SA) at both anode and cathode respectively by the co-electrolysis of polybutylene succinate (PBS) waste plastics and biomass-derived maleic acid (MA) for the first time. To this end, Cr3+-Ni(OH)2 electrocatalyst featuring much enhanced 1,4-butanediol (BDO) oxidation reaction (BOR) activity has been synthesized and the role of doped Cr has been revealed as an "electron puller" to accelerate the rate-determining step (RDS) in the Ni2+/Ni3+ cycling. Impressively, an extra-high SA production rate of 3.02 g h-1 and ultra-high apparent Faraday efficiency towards SA (FEapparent=181.5 %) have been obtained. A carbon dioxide-assisted sequential precipitation approach has been developed to produce high-purity SA and byproduct NaHCO3 solids. Preliminary techno-economic analysis demonstrates that the reported system is economically profitable and promising for future industrial applications.