Essential features of weak current for excellent enhancement of NOx reduction over monoatomic V-based catalyst

Human society is facing increasingly serious problems of environmental pollution and energy shortage, and up to now, achieving high NH3-SCR activity at ultra-low temperatures (<150 °C) remains challenging for the V-based catalysts with V content below 2%. In this study, the monoatomic V-based catalyst under the weak current-assisted strategy can completely convert NOx into N2 at ultra-low temperature with V content of 1.36%, which shows the preeminent turnover frequencies (TOF145 °C = 1.97×10-3 s-1). The improvement of catalytic performance is mainly attributed to the enhancement catalysis of weak current (ECWC) rather than electric field, which significantly reduce the energy consumption of the catalytic system by more than 90%. The further mechanism research for the ECWC based on a series of weak current-assisted characterization means and DFT calculations confirms that migrated electrons mainly concentrate around the V single atoms and increase the proportion of antibonding orbitals, which make the V-O chemical bond weaker (electron scissors effect) and thus accelerate oxygen circulation. The novel current-assisted catalysis in the present work can potentially apply to other environmental and energy fields.

Distributed electrified heating for efficient hydrogen production

This study introduces a distributed electrified heating approach that is able to innovate chemical engineering involving endothermic reactions. It enables rapid and uniform heating of gaseous reactants, facilitating efficient conversion and high product selectivity at specific equilibrium. Demonstrated in catalyst-free CH4 pyrolysis, this approach achieves stable production of H2 (530 g h-1 L reactor -1) and carbon nanotube/fibers through 100% conversion of high-throughput CH4 at 1150 °C, surpassing the results obtained from many complex metal catalysts and high-temperature technologies. Additionally, in catalytic CH4 dry reforming, the distributed electrified heating using metallic monolith with unmodified Ni/MgO catalyst washcoat showcased excellent CH4 and CO2 conversion rates, and syngas production capacity. This innovative heating approach eliminates the need for elongated reactor tubes and external furnaces, promising an energy-concentrated and ultra-compact reactor design significantly smaller than traditional industrial systems, marking a significant advance towards more sustainable and efficient chemical engineering society.

Effect of Hydrogen Addition on Coke Formation and Product Distribution in Catalytic Coupling of Methane

The effect of hydrogen addition on catalytic nonoxidative coupling of methane at 1000 °C was investigated. Experiments were performed at varying ratios between the catalyst and the postcatalytic volume to discern the effect of hydrogen on the catalytic reaction as well as on the gas-phase reaction. Adding 10% H2 decreases the methane conversion by a factor of 2, almost independent of the ratio between the catalyst and the postcatalytic residence time. The effect on the conversion is mostly determined by gas-phase chemistry. Hydrogen addition has no influence on the C2 hydrocarbon yield, whereas aromatic selectivity is significantly reduced. Changes in selectivity are attributed to changes in methane conversion. Quantitative determination of the amount of coke deposited on the catalyst reveals a decrease by 1 order of magnitude when dosing up to 10% H2, while carbon deposits-downstream of the catalyst bed are suppressed to a much lower extent. These results suggest a process in which the produced hydrogen is partly recycled, maximizing the carbon selectivity to C2 hydrocarbons while minimizing both aromatics and, most crucially, formation of coke on the catalyst as well as further deposits-downstream.

Spatial Confinement of Pt Nanoparticles in Carbon Nanotubes for Efficient and Selective H2 Evolution from Methanol

H2 generation from methanol-water mixtures often requires high pressure and high temperature (200-300 °C). However, CO can be easily generated and poison the catalytic system under such high temperature. Therefore, it is highly desirable to develop the efficient catalytic systems for H2 production from methanol at room temperature, even at sub-zero temperatures. Herein, carbon nanotube-supported Pt nanocomposites are designed and synthesized as high-performance nano-catalysts, via stabilization of Pt nanoparticles onto carbon nanotube (CNT), for H2 production upon methanol dehydrogenation at sub-zero temperatures. Therein, the optimal Pt/CNT nanocomposite presents the superior catalytic performance in H2 production upon methanol dehydrogenation at the expense of B2(OH)4, with the TOF of 299.51 min-130 oC. Compared with other common carriers, Pt/CNT exhibited the highest catalytic performance in H2 production, emphasizing the critical role of CNT in methanol dehydrogenation. The confinement of Pt nanoparticles by CNTs is conducive to inhibiting the aggregation of Pt nanoparticles, thereby significantly increasing its catalytic performance and stability. The kinetic study, detailed mechanistic insights, and density functional theory (DFT) calculation confirm that the breaking of O─H bond of CH3OH is the rate-controlling step for methanol dehydrogenation, and both H atoms of H2 are supplied by methanol. Interestingly, H2 is also successfully produced from methanol dehydrogenation at -10 °C, which absolutely solves the freezing problem in the H2 evolution upon water-splitting reaction.

Role of H2O in Catalytic Conversion of C1 Molecules

Due to their role in controlling global climate change, the selective conversion of C1 molecules such as CH4, CO, and CO2 has attracted widespread attention. Typically, H2O competes with the reactant molecules to adsorb on the active sites and therefore inhibits the reaction or causes catalyst deactivation. However, H2O can also participate in the catalytic conversion of C1 molecules as a reactant or a promoter. Herein, we provide a perspective on recent progress in the mechanistic studies of H2O-mediated conversion of C1 molecules. We aim to provide an in-depth and systematic understanding of H2O as a promoter, a proton-transfer agent, an oxidant, a direct source of hydrogen or oxygen, and its influence on the catalytic activity, selectivity, and stability. We also summarize strategies for modifying catalysts or catalytic microenvironments by chemical or physical means to optimize the positive effects and minimize the negative effects of H2O on the reactions of C1 molecules. Finally, we discuss challenges and opportunities in catalyst design, characterization techniques, and theoretical modeling of the H2O-mediated catalytic conversion of C1 molecules.

Progress in Anode Stability Improvement for Seawater Electrolysis to Produce Hydrogen

Seawater electrolysis for hydrogen production is a sustainable and economical approach that can mitigate the energy crisis and global warming issues. Although various catalysts/electrodes with excellent activities have been developed for high-efficiency seawater electrolysis, their unsatisfactory durability, especially for anodes, severely impedes their industrial applications. In this review, attention is paid to the factors that affect the stability of anodes and the corresponding strategies for designing catalytic materials to prolong the anode's lifetime. In addition, two important aspects-electrolyte optimization and electrolyzer design-with respect to anode stability improvement are summarized. Furthermore, several methods for rapid stability assessment are proposed for the fast screening of both highly active and stable catalysts/electrodes. Finally, perspectives on future investigations aimed at improving the stability of seawater electrolysis systems are outlined.

Actively Learned Optimal Sustainable Operation of Plasma-Catalyzed Methane Bireforming on La0.7Ce0.3NiO3 Perovskite Catalyst

Plasma-catalytic bireforming of methane was studied and actively optimized using a La0.7Ce0.3NiO3 perovskite catalyst via experimentation in tandem with response surface modeling. Plasma power, inlet flow rate, temperature, CO2/CH4 ratio, and steam concentration were tuned to maximize a variety of process- and sustainability-based metrics. Analysis of the optimal conditions (with respect to different metrics) with and without the catalyst reveals that dry reforming is driven largely via noncatalytic reactions, while steam reforming and water gas shift reactions require the catalyst. The experimental outcome demonstrated that under optimum reaction conditions using the La0.7Ce0.3NiO3 catalyst it is possible to minimize global warming potential (GWP), in terms of inferred CO2 footprint normalized to hydrogen throughput, resulting in maximizing hydrogen yield through steam reforming (and water gas shift reactions) at an SEI of ≈12 eV/molecule. Furthermore, the highest CH4 conversion reached was 87% while the catalyst showed good activity stability in DBD plasma experiments.The actively learned iterative optimization procedure developed in this work allows for a direct juxtaposition of thermal (heat needed to make steam and heat the plasma reactor) and electrical (power requirement for plasma generation) carbon footprints in a highly nonlinear multivariate process. Furthermore, the corresponding GWP was calculated using a conventional electricity mix, wind electricity, and solar electricity, allowing a direct sustainability assessment in catalyst-assisted plasma conversion of carbonaceous feedstock to H2 and CO.

Significantly Enhanced Energy-Saving H2 Production Coupled with Urea Oxidation by Low- and Non-Pt Anchored on NiS-Based Conductive Nanofibers

Rational designing electrocatalysts is of great significance for realizing high-efficiency H2 production in the water splitting process. Generally, reducing the usage of precious metals and developing low-potential nucleophiles oxidation reaction to replace anodic oxygen evolution reaction (OER) are efficient strategies to promote H2 generation. Here, NiS-coated nickel-carbon nanofibers (NiS@Ni-CNFs) are prepared for low-content Pt deposition (Pt-NiS@Ni-CNFs) to attain the alkaline HER catalyst. Due to the reconfiguration of NiS phase and synergistic effect between Pt and nickel sulfides, the Pt-NiS@Ni-CNFs catalyst shows a high mass activity of 2.74-fold of benchmark Pt/C sample. In addition, the NiS@Ni-CNFs catalyst performs a superior urea oxidation reaction (UOR) activity with the potential of 1.366 V versus reversible hydrogen electrode (RHE) at 10 mA cm-2 , which demonstrates the great potential in the replacement of OER. Thus, a urea-assisted water splitting electrolyzer of Pt-NiS@Ni-CNFs (cathode)||NiS@Ni-CNFs (anode) is constructed to exhibit small voltages of 1.44 and 1.65 V to reach 10 and 100 mA cm-2 , which is much lower than its overall water splitting process, and presents a 6.5-fold hydrogen production rate enhancement. This work offers great opportunity to design new catalysts toward urea-assisted water splitting with significantly promoted hydrogen productivity and reduced energy consumption.

Environmental impact assessment of a combined bioprocess for hydrogen production from food waste

With the growth of population and the development of economy, the food waste (FW) and energy shortage issues are getting great attentions. In this study, the environmental performance of a biorefinery of enzymatic hydrolysis and fermentation for hydrogen production from FW (FW-H2) was investigated by life cycle assessment (LCA) in terms of greenhouse gas (GHG) emissions and non-renewable energy use (NREU). It was found that the gas compression, electricity and FW transport were the major environmental hotspots in the FW-H2 process. The GHG emissions of 10.1 kg CO2 eq and NREU of 104 MJ were obtained from per kg hydrogen production through the whole process. The environmental impacts of the FW-H2 process were lower than the conventional processes for hydrogen production, such as steam methane reforming and electrolysis with grid. Sensitivity analysis demonstrated that the efforts in environmental hotspots, especially in gas compression, could result in the improvement of environmental impacts of the FW-H2 process. The GHG emissions and NREU could reduce to 89.2 % and 89.4 % with a 20 % reduction of energy consumption for gas compression. Different allocation methods (economic allocation, mass allocation, no allocation and system expansion method) applied for LCA analysis could provide a significant influence of environmental impacts in the FW-H2 process. The results obtained from this study could lead to further research into resource recycling from waste and would ultimately contribute to the development of circular economy.

Electrification-Enhanced Low-Temperature NOx Storage-Reduction on Pt and K Co-Supported Antimony-Doped Tin Oxides

NOx storage-reduction (NSR), a promising approach for removing NOx pollutants from diesel vehicles, remains elusive to cope with the increasingly lower exhaust temperatures (especially below 250 °C). Here, we develop a conceptual electrified NSR strategy, where electricity with a low input power (0.5-4 W) is applied to conductive Pt and K co-supported antimony-doped tin oxides (Pt-K/ATO), with C3H6 as a reductant. The ignition temperature for 10% NOx conversion is nearly 100 °C lower than that of the traditional thermal counterpart. Furthermore, reducing the power in the fuel-lean period relative to that in the fuel-rich period increases the maximum energy efficiency by 23%. Electrically driven release of lattice oxygen is revealed to play vital roles in multiple steps in NSR, including NO adsorption, desorption, and reduction, for improved NSR activity. This work provides an electrification strategy for developing high-activity NSR catalysis utilizing electricity onboard hybrid vehicles.

Emerging Liquid Metal Catalysts

Catalysts serve pivotal roles in facilitating the development of sustainable energy systems on a global scale. Liquid metal usually refers to metal that is liquid below 330 °C, also known as low melting point metal. Liquid metal has emerged as an intriguing catalyst due to its commendable electrical conductivity, favorable fluidity, solubility in metals, phase transition capabilities, and modifiable oxide surface, thereby presenting a plethora of prospects for diverse catalytic reactions. In this Perspective, we elucidate the four primary merits of liquid metal catalysts: resistance to coking, the ability to tune elemental composition, the potential for structural transformation, and the capacity to inhibit coalescence. In light of this, a comprehensive summary is presented on the research advancements pertaining to liquid metal in methane pyrolysis, alkane dehydrogenation, carbon dioxide reduction, alcohol oxidation, and various other catalytic reactions. Finally, the challenges and prospects of liquid metal catalysts are elucidated.

Microwave-assisted, performance-advantaged electrification of propane dehydrogenation

Nonoxidative propane dehydrogenation (PDH) produces on-site propylene for value-added chemicals. While commercial, its modest selectivity and catalyst deactivation hamper the process efficiency and limit operation to lower temperatures. We demonstrate PDH in a microwave (MW)-heated reactor over PtSn/SiO2 catalyst pellets loaded in a SiC monolith acting as MW susceptor and a heat distributor while ensuring comparable conditions with conventional reactors. Time-on-stream experiments show active and stable operation at 500°C without hydrogen addition. Upon increasing temperature or feed partial pressure at high space velocity, catalysts under MWs show resistance in coking and sintering, high activity, and selectivity, starkly contrasting conventional reactors whose catalyst undergoes deactivation. Mechanistic differences in coke formation are exposed. Gas-solid temperature gradients are computationally investigated, and nanoscale temperature inhomogeneities are proposed to rationalize the different performances of the heating modes. The approach highlights the great potential of electrification of endothermic catalytic reactions.

A step-by-step strategy to design active and stable quaternary intermetallic compounds for the hydrogen evolution reaction

Multinary intermetallic compounds with rich chemical compositions enable one to achieve a logical design for desired materials based on the required function. In this work, we have demonstrated a step-by-step strategy to design a quaternary intermetallic compound that exhibits highly active and stable performance for the hydrogen evolution reaction (HER). With binary intermetallic TaCo2 as the starting point, the minor inclusion of a ductile Cu element in TaCo2 to form ternary TaCu0.25Co1.75 can substantially lower the degradation rate from ca. 20% to 5% after sintering treatment (i.e., enhance connectivity between particles). However, the overpotential at a current density of 10 mA cm-2 (η10) increases by ca. 20 mV from TaCo2 to TaCu0.25Co1.75. Further incorporation of a HER active Ru element to cast quaternary TaCu0.125Ru0.125Co1.75 can decrease ca. 70 mV of η10 while maintaining long-term stability. This proves that one can design functional intermetallic compounds intentionally, which may be extended to different fields of application.

Methane-to-chemicals: a pathway to decarbonization

The utilization of methane for chemical production, often considered as the future of petrochemistry, historically could not compete economically with conventional processes due to higher investment costs. Achieving sustainability and decarbonization of the downstream industry by integration with a methane-to-chemicals process may provide an opportunity to unlock the future for these technologies. Gas-to-chemicals is an efficient tool to boost the decarbonization potential of renewable energy. While the current implementation of carbon capture utilization and storage (CCUS) technologies is of great importance for industrial decarbonization, a shift to greener CO2-free processes and CO2 utilization from external sources for manufacturing valuable goods is highly preferred. This review outlines potential options for how a methane-to-chemicals process could support decarbonization of the downstream industry.

Smart manufacturing inspired approach to research, development, and scale-up of electrified chemical manufacturing systems

As renewable electricity becomes cost competitive with fossil fuel energy sources and environmental concerns increase, the transition to electrified chemical and fuel synthesis pathways becomes increasingly desirable. However, electrochemical systems have traditionally taken many decades to reach commercial scales. Difficulty in scaling up electrochemical synthesis processes comes primarily from difficulty in decoupling and controlling simultaneously the effects of intrinsic kinetics and charge, heat, and mass transport within electrochemical reactors. Tackling this issue efficiently requires a shift in research from an approach based on small datasets, to one where digitalization enables rapid collection and interpretation of large, well-parameterized datasets, using artificial intelligence (AI) and multi-scale modeling. In this perspective, we present an emerging research approach that is inspired by smart manufacturing (SM), to accelerate research, development, and scale-up of electrified chemical manufacturing processes. The value of this approach is demonstrated by its application toward the development of CO₂ electrolyzers.

Microwave-enhanced hydrogen production: a review

Currently, the massive use of fossil fuels, which still serve as the dominant global energy, has led to the release of large amounts of greenhouse gases. Providing abundant, clean, and safe renewable energy is one of the major technical challenges for humankind. Nowadays, hydrogen-based energy is widely considered a potentially ideal energy carrier that could provide clean energy in the fields of transportation, heat and power generation, and energy storage systems, almost without any impact on the environment after consumption. However, a smooth energy transition from fossil-fuel-based energy to hydrogen-based energy must overcome a number of key challenges that require scientific, technological, and economic support. To accelerate the hydrogen energy transition, advanced, efficient, and cost-effective methods for producing hydrogen from hydrogen-rich materials need to be developed. Therefore, in this study, a new alternative method based on the use of microwave (MW) heating technology in enhanced hydrogen production pathways from plastic, biomass, low-carbon alcohols, and methane pathways compared with conventional heating methods is discussed. Furthermore, the mechanisms of MW heating, MW-assisted catalysis, and MW plasma are also discussed. MW-assisted technology usually has the advantages of low energy consumption, easy operation, and good safety practices, which make it a promising solution to supporting the future hydrogen society.

Algae Pyrolysis in Molten NaOH-Na2CO3 for Hydrogen Production

Biomass pyrolysis within the alkaline molten salt is attractive due to its ability to achieve high hydrogen yield under relatively mild conditions. However, poor contact between biomass, especially the biomass pellet, and hydroxide during the slow heating process, as well as low reaction temperatures, become key factors limiting the hydrogen production. To address these challenges, fast pyrolysis of the algae pellet in molten NaOH-Na₂CO₃ was conducted at 550, 650, and 750 °C. Algae were chosen as feedstock for their high photosynthetic efficiency and growth rate, and the concept of coupling molten salt with concentrated solar energy was proposed to address the issue of high energy consumption at high temperatures. At 750 °C, the pollutant gases containing Cl and S were completely removed, and the HCN removal rate reached 44.92%. During the continuous pyrolysis process, after a slight increase, the hydrogen yield remained stable at 71.48 mmol/g-algae and constituted 86.10% of the gas products, and a minimum theoretical hydrogen production efficiency of algae can reach 84.86%. Most importantly, the evolution of physicochemical properties of molten NaOH-Na₂CO₃ was revealed for the first time. Combined with the conversion characteristics of feedstock and gas products, this study provides practical guidance for large-scale application of molten salt including feedstock, operation parameters, and post-treatment process.

Direct S-H Evidence Revealing the Photo-electrocatalytic Hydrogen Evolution Reaction Mechanism on CdS Using Surface-Enhanced Raman Spectroscopy

Photoelectrocatalytic water splitting using metal sulfides is a promising method for green hydrogen production. However, in situ probing of the hydrogen evolution reaction (HER) on sulfides with excellent performance remains a challenge. Here, we construct Au@CdS core-shell nanoparticles to study the HER on CdS, a typical HER catalyst, by surface-enhanced Raman spectroscopy (SERS) using a "borrowing" strategy. We directly capture the spectroscopic evidence of S-H intermediate under HER condition, further verified by isotopic experiments. Moreover, the population of S-H intermediates is improved by injecting charge carriers through light illumination and the S-H bond is weakened by introducing Pt to form a Au@Pt@CdS structure to change the interfacial electronic structure, both of them resulting in significant HER performance improvement. These findings can deepen the understanding of the HER mechanism and offer strategies for designing of cost-effective HER catalyst with high performance.

Ni nanoparticles supported on Al2O3 + La2O3 yolk-shell catalyst for photo-assisted thermal decomposition of methane

Catalytic methane decomposition (CMD) has emerged as an appealing technology for large-scale production of H₂ and carbon nanostructures from natural gas. As the CMD process is mildly endothermic, the application of concentrated renewable energy sources such as solar energy under a low-temperature regime could potentially represent a promising approach towards CMD process operation. Herein, Ni/Al₂O₃-La₂O₃ yolk-shell catalysts are fabricated using a straightforward single-step hydrothermal approach and tested for their performance in photothermal CMD. We show that the morphology of the resulting materials, dispersion and reducibility of Ni nanoparticles, and nature of metal-support interactions can be tuned by addition of varying amounts of La. Notably, the addition of an optimal amount of La (Ni/Al-20La) improved the H₂ yield and catalyst stability relative to the base Ni/Al₂O₃ material, while also favoring base growth of carbon nanofibers. Additionally, we show for the first time a photothermal effect in CMD, whereby the introduction of 3 suns light irradiation at a constant bulk temperature of 500 °C reversibly increased the H₂ yield of catalyst by about 1.2 times relative to the rate in the dark, accompanied by a decrease in apparent activation energy from 41.6 kJ mol^-1 to 32.5 kJ mol^-1. The light irradiation further suppressed undesirable CO co-production at low temperatures. Our work reveals photothermal catalysis as a promising route for CMD while providing an insightful understanding of the roles of modifier in enriching methane activation sites on Al₂O₃-based catalysts.

Electrified hydrocarbon-to-oxygenates coupled to hydrogen evolution for efficient greenhouse gas mitigation

Chemicals manufacture is among the top greenhouse gas contributors. More than half of the associated emissions are attributable to the sum of ammonia plus oxygenates such as methanol, ethylene glycol and terephthalic acid. Here we explore the impact of electrolyzer systems that couple electrically-powered anodic hydrocarbon-to-oxygenate conversion with cathodic H₂ evolution reaction from water. We find that, once anodic hydrocarbon-to-oxygenate conversion is developed with high selectivities, greenhouse gas emissions associated with fossil-based NH₃ and oxygenates manufacture can be reduced by up to 88%. We report that low-carbon electricity is not mandatory to enable a net reduction in greenhouse gas emissions: global chemical industry emissions can be reduced by up to 39% even with electricity having the carbon footprint per MWh available in the United States or China today. We conclude with considerations and recommendations for researchers who wish to embark on this research direction.

δ-MnO2 decorated layered double oxides in-situ grown on nickel foam towards electrothermal catalysis of n-heptane

Energy-saving and efficient monolithic catalysts are hotspots of catalytic purification of industrial gaseous pollutants. Here, we have developed an electrothermal catalytic mode, in which the ignition temperature required for the reaction is provided by Joule heat generated when the current flows through the catalyst. In this paper, Mn/NiAl/NF, Mn/NiFe/NF and Mn/NF metal-based monolithic catalysts were prepared using nickel foam (NF) as the carrier for thermal and electrothermal catalysis of n-heptane. The results indicated that Mn-based monolithic catalysts exhibit high activity in thermal and electrothermal catalysis. Mn/NiFe/NF achieve conversion of n-heptane more than 99% in electrothermal catalysis under a direct-current (DC) power of 6 W, and energy-saving is 54% compared with thermal catalysis. In addition, the results indicated that the introduction of NiAl (or NiFe) greatly enhanced the catalytic activity of Mn/NF, which attributed to the higher specific surface area, Mn³⁺/Mn⁴⁺, Ni³⁺/Ni²⁺, adsorbed oxygen species (O_ads)/lattice oxygen species (O_latt), redox performance of the catalyst. Electrothermal catalytic activity was significantly higher than thermal catalytic activity before complete conversion, which may be related to electronic effects. Besides, Mn/NiFe/NF has good cyclic and long-term stability in electrothermal catalysis. This paper provided a theoretical basis for applying electrothermal catalysis in the field of VOCs elimination.

Depolymerization of plastics by means of electrified spatiotemporal heating

Depolymerization is a promising strategy for recycling waste plastic into constituent monomers for subsequent repolymerization1. However, many commodity plastics cannot be selectively depolymerized using conventional thermochemical approaches, as it is difficult to control the reaction progress and pathway. Although catalysts can improve the selectivity, they are susceptible to performance degradation2. Here we present a catalyst-free, far-from-equilibrium thermochemical depolymerization method that can generate monomers from commodity plastics (polypropylene (PP) and poly(ethylene terephthalate) (PET)) by means of pyrolysis. This selective depolymerization process is realized by two features: (1) a spatial temperature gradient and (2) a temporal heating profile. The spatial temperature gradient is achieved using a bilayer structure of porous carbon felt, in which the top electrically heated layer generates and conducts heat down to the underlying reactor layer and plastic. The resulting temperature gradient promotes continuous melting, wicking, vaporization and reaction of the plastic as it encounters the increasing temperature traversing the bilayer, enabling a high degree of depolymerization. Meanwhile, pulsing the electrical current through the top heater layer generates a temporal heating profile that features periodic high peak temperatures (for example, about 600 °C) to enable depolymerization, yet the transient heating duration (for example, 0.11 s) can suppress unwanted side reactions. Using this approach, we depolymerized PP and PET to their monomers with yields of about 36% and about 43%, respectively. Overall, this electrified spatiotemporal heating (STH) approach potentially offers a solution to the global plastic waste problem.

Regulating Hollow Carbon Cage Supported NiCo Alloy Nanoparticles for Efficient Electrocatalytic Hydrogen Evolution Reaction

The NiCo alloy is one of the most promising alternatives to the noble-metal electrocatalysts for the hydrogen evolution reaction (HER); however, its performance is largely restricted by insufficient active sites and low surface area. Here, we fabricated a hierarchical hollow carbon cage supported NiCo alloy (denoted as HC NiCo/C) and a bulk NiCo alloy (denoted as NiCo) by reduction of a partially ZIF-67 etched ZIF-67@NiCo-LDH (LDH = layered double hydroxide) precursor and a fully ZIF-67 etched NiCo-LDH precursor, respectively. The as-prepared HC NiCo/C, in which the Ni₂₉Co₇₁ alloy nanocrystals with an average 6 nm size were encapsulated in graphitic carbon layers, provided a vastly increased electrochemically active surface area (ca. 13 times than the NiCo) and abundant catalytic active sites, which resulted in a higher HER performance with an overpotential of 99 mV than the 198 mV for NiCo at 10 mA cm^-2. Detailed experimental results suggested that only the HC NiCo/C possessed the active alloy surface composed of unsaturated Ni⁰ and Co⁰ atoms, and both the metal-support interaction and alloying effect influenced the electronic structure of Co and Ni in HC NiCo/C, whereas the NiCo exhibited pure Ni surface. Theoretical calculations further revealed the Ni₂₉Co₇₁ alloy surface in HC NiCo/C possessed the appropriate adsorption energy of the intermediate state (adsorbed H*). This work provided new insight into the construction of the stable small-sized bimetallic alloy nanocatalysts by regulating the reduction precursors.

Decoupled alkaline water electrolysis by a K0.5MnO2-Ti mediator via K-ion insertion/extraction

Conventional one-step water electrolyzers generate H₂ accompanied by O₂ evolution, and may cause gas mixing and high cell voltage inputs. Herein, using the potassium ion battery material of K_0.5MnO₂-Ti as a mediator, we effectively decoupled the H₂ and O₂ evolution of alkaline water electrolysis temporally, thereby achieving a membrane-free pathway for H₂ production. As a mediator electrode for charge storage, the K_0.5MnO₂-Ti exhibited a stable capacity of 100 mA h g^-1 at 0.1 A g^-1 owing to the reversible K-ion insertion/extraction mechanism. The decoupled water electrolysis device exhibited the step voltages for hydrogen and oxygen production of 1.02 and 0.57 V at 5 mA, respectively. A nearly unity Faradaic efficiency and sustained production of pure H₂ has been demonstrated at a constant current density. We anticipate that this mediator demonstrated here may provide a route for the practical application of the decoupling strategy.

Greenhouse gas emissions from nitrogen fertilizers could be reduced by up to one-fifth of current levels by 2050 with combined interventions

Food security relies on nitrogen fertilizers, but its production and use account for approximately 5% of global greenhouse gas (GHG) emissions. Meeting climate change targets requires the identification and prioritization of interventions across the whole life cycle of fertilizers. Here we have mapped the global flows of synthetic nitrogen fertilizers and manure and their corresponding GHG emissions across their life cycle. We have then explored the maximum mitigation potential of various interventions to reduce emissions by 2050. We found that approximately two-thirds of fertilizer emissions take place after their deployment in croplands. Increasing nitrogen-use efficiency is the single most effective strategy to reduce emissions. Yet this should be combined with decarbonization of fertilizer production. Using currently available technologies, GHG emissions of fertilizers could be reduced up to approximately one-fifth of current levels by 2050.

A Carbon-Negative Hydrogen Production Strategy: CO2 Selective Capture with H2 Production

We reported a strategy of carbon-negative H₂ production in which CO₂ capture was coupled with H₂ evolution at ambient temperature and pressure. For this purpose, carbonate-type Cu_x Mg_y Fe_z layered double hydroxide (LDH) was preciously constructed, and then a photocatalysis reaction of interlayer CO₃ ^2- reduction with glycerol oxidation was performed as driving force to induce the electron storage on LDH layers. With the participation of pre-stored electrons, CO₂ was captured to recover interlayer CO₃ ^2- in presence of H₂ O, accompanied with equivalent H₂ production. During photocatalysis reaction, Cu_0.6 Mg_1.4 Fe₁ exhibited a decent CO evolution amount of 1.63 mmol g^-1 and dihydroxyacetone yield of 3.81 mmol g^-1 . In carbon-negative H₂ production process, it showed an exciting CO₂ capture quantity of 1.61 mmol g^-1 and H₂ yield of 1.44 mmol g^-1 . Besides, this system possessed stable operation capability under simulated flu gas condition with negligible performance loss, exhibiting application prospect.

Methane Oxidation to Methanol

The direct transformation of methane to methanol remains a significant challenge for operation at a larger scale. Central to this challenge is the low reactivity of methane at conditions that can facilitate product recovery. This review discusses the issue through examination of several promising routes to methanol and an evaluation of performance targets that are required to develop the process at scale. We explore the methods currently used, the emergence of active heterogeneous catalysts and their design and reaction mechanisms and provide a critical perspective on future operation. Initial experiments are discussed where identification of gas phase radical chemistry limited further development by this approach. Subsequently, a new class of catalytic materials based on natural systems such as iron or copper containing zeolites were explored at milder conditions. The key issues of these technologies are low methane conversion and often significant overoxidation of products. Despite this, interest remains high in this reaction and the wider appeal of an effective route to key products from C-H activation, particularly with the need to transition to net carbon zero with new routes from renewable methane sources is exciting.

Electrosynthesis of ammonia with high selectivity and high rates via engineering of the solid-electrolyte interphase

Ammonia is a large-scale commodity essential to fertilizer production, but the Haber-Bosch process leads to massive emissions of carbon dioxide. Electrochemical ammonia synthesis is an attractive alternative pathway, but the process is still limited by low ammonia production rate and faradaic efficiency. Herein, guided by our theoretical model, we present a highly efficient lithium-mediated process enabled by using different lithium salts, leading to the formation of a uniform solid-electrolyte interphase (SEI) layer on a porous copper electrode. The uniform lithium-fluoride-enriched SEI layer provides an ammonia production rate of 2.5 ± 0.1 μmol s^-1 cm_geo ^-2 at a current density of -1 A cm_geo ^-2 with 71% ± 3% faradaic efficiency under 20 bar nitrogen. Experimental X-ray analysis reveals that the lithium tetrafluoroborate electrolyte induces the formation of a compact and uniform SEI layer, which facilitates homogeneous lithium plating, suppresses the undesired hydrogen evolution as well as electrolyte decomposition, and enhances the nitrogen reduction.

Supra Hydrolytic Catalysis of Ni3 Fe/rGO for Hydrogen Generation

Light metal hydrolysis for hydrogen supply is well suited for portable hydrogen fuel cells. The addition of catalysts can substantially aid Mg hydrolysis. However, there is a lack of clear catalytic mechanism to guide the design of efficient catalysts. In this work, the essential role of nanosized catalyst (Ni₃ Fe/rGO) in activating micro-sized Mg with ultra-rapid hydrolysis process is investigated for the first time. Here, an unprecedented content of 0.2 wt% Ni₃ Fe/rGO added Mg can release 812.4 mL g^-1 hydrogen in just 60 s at 30 °C. Notably, an impressive performance with a hydrogen yield of 826.4 mL g^-1 at 0 °C in only 30 s is achieved by the Mg-2 wt% Ni₃ Fe/rGO, extending the temperature range for practical applications of hydrolysis. Moreover, the four catalysts (Ni₃ Fe/rGO, Ni₃ Fe, Ni/rGO, Fe/rGO) are designed to reveal the influence of composition, particle size, and dispersion on catalytic behavior. Theoretical studies corroborate that the addition of Ni₃ Fe/rGO accelerates the electron transfer and coupling processes and further provides a lower energy barrier diffusion path for hydrogen. Thus, a mechanism concerning the catalyst as migration relay is proposed. This work offers guidelines designing high-performance catalysts especially for activating the hydrolysis of micro-sized light weight metals.

Low Temperature Nano Mechano-electrocatalytic CH4 Conversion

Transforming natural resources to energy sources, such as converting CH₄ to H₂ and carbon, at high efficiency and low cost is crucial for many industries and environmental sustainability. The high temperature requirement of CH₄ conversion regarding many of the current methods remains a critical bottleneck for their practical uptake. Here we report an approach based on gallium (Ga) liquid metal droplets, Ni(OH)₂ cocatalysts, and mechanical energy input that offers low-temperature and scalable CH₄ conversion into H₂ and carbon. Mainly driven by the triboelectric voltage, originating from the joint contributions of the cocatalysts during agitation, CH₄ is converted at the Ga and Ni(OH)₂ interface through nanotribo-electrochemical reaction pathways. The efficiency of the system is enhanced when the reaction is performed at an increased pressure. The dehydrogenation of other nongaseous hydrocarbons using this approach is also demonstrated. This technology presents a possible low energy route for CH₄ conversion without involving high temperature and harsh operating conditions.

Electrodissolution-Coupled Hafnium Alkoxide Synthesis with High Environmental and Economic Benefits

The conventional thermal method of preparing hafnium alkoxides [Hf(OR)₄ , R=alkyl] - excellent precursors for gate-dielectric HfO₂ on semiconductors - is severely hindered by its unsatisfactory environmental and economic burdens. Herein, we propose a promising electrodissolution-coupled Hf(OR)₄ synthesis (EHS) system for green and efficient electrosynthesis of Hf(OR)₄ . The operational principle of the electrically driven system consists of two simultaneous heterogeneous reactions of Hf dissolution and alcohol dehydrogenation, plus a spontaneous solution-based combination reaction. In applying ethanol as solvent and Hf metal as electrodissolution medium, we achieved waste-free production of high-purity hafnium ethoxide [Hf(OEt)₄ ] with an equivalent "a concomitant" reduction in CO₂ emission of 187.33 g CO₂ per kg Hf(OEt)₄ and a high net profit of 30 477 USD per kg Hf(OEt)₄ . This system is very competitive with the thermal process, which unavoidably releases substantial waste and CO₂ for a net profit of 27 700 USD per kg Hf(OEt)₄ . We anticipate that the environmental and economic benefits of the EHS process could pave the way for its practical application.

Recent Advances in Perovskite Catalysts for Efficient Overall Water Splitting

Hydrogen is considered a promising clean energy vector with the features of high energy capacity and zero-carbon emission. Water splitting is an environment-friendly and effective route for producing high-purity hydrogen, which contains two important half-cell reactions, namely, the anodic oxygen evolution reaction (OER) and the cathodic hydrogen evolution reaction (HER). At the heart of water splitting is high-performance electrocatalysts that efficiently improve the rate and selectivity of key chemical reactions. Recently, perovskite oxides have emerged as promising candidates for efficient water splitting electrocatalysts owing to their low cost, high electrochemical stability, and compositional and structural flexibility allowing for the achievement of high intrinsic electrocatalytic activity. In this review, we summarize the present research progress in the design, development, and application of perovskite oxides for electrocatalytic water splitting. The emphasis is on the innovative synthesis strategies and a deeper understanding of structure–activity relationships through a combination of systematic characterization and theoretical research. Finally, the main challenges and prospects for the further development of more efficient electrocatalysts based on perovskite oxides are proposed. It is expected to give guidance for the development of novel non-noble metal catalysts in electrochemical water splitting.

Programmable heating and quenching for efficient thermochemical synthesis

Conventional thermochemical syntheses by continuous heating under near-equilibrium conditions face critical challenges in improving the synthesis rate, selectivity, catalyst stability and energy efficiency, owing to the lack of temporal control over the reaction temperature and time, and thus the reaction pathways^1-3. As an alternative, we present a non-equilibrium, continuous synthesis technique that uses pulsed heating and quenching (for example, 0.02 s on, 1.08 s off) using a programmable electric current to rapidly switch the reaction between high (for example, up to 2,400 K) and low temperatures. The rapid quenching ensures high selectivity and good catalyst stability, as well as lowers the average temperature to reduce the energy cost. Using CH₄ pyrolysis as a model reaction, our programmable heating and quenching technique leads to high selectivity to value-added C₂ products (>75% versus <35% by the conventional non-catalytic method and versus <60% by most conventional methods using optimized catalysts). Our technique can be extended to a range of thermochemical reactions, such as NH₃ synthesis, for which we achieve a stable and high synthesis rate of about 6,000 μmol g_Fe^-1 h^-1 at ambient pressure for >100 h using a non-optimized catalyst. This study establishes a new model towards highly efficient non-equilibrium thermochemical synthesis.

Ni-CeO2/SBA-15 Catalyst Prepared by Glycine-Assisted Impregnation Method for Low-Temperature Dry Reforming of Methane

Developing low-temperature nickel-based catalysts with good resistance to coking and sintering for dry reforming of methane (DRM) is of great significance. In this work, Ni (5 wt%) and CeO2 (5 wt%) were supported on SBA-15 porous material by glycine-assisted impregnation method to obtain Ni-CeO2/SBA-15-G catalyst. XRD and TEM results showed that the addition of glycine can effectively promote the dispersion of NiO and CeO2 in the pores of SBA-15. H2-TPR and XPS results confirmed the formation of stronger metal-support interaction. In addition, after the addition of glycine, the NixCe1−xOy solid solution content was increased significantly, meanwhile, the Ce3+ concentration was increased from 31% to 49%, accompanied by more oxygen vacancies and generation of active oxygen species. For the above reasons, Ni-CeO2/SBA-15-G had better catalytic performance in the low-temperature DRM test (20 h, 600 °C) with high GHSV (600,000 mL/gcat/h), its CH4 conversion after reaction of 20 h was 2 times that of Ni-CeO2/SBA-15-C catalyst prepared by a conventional impregnation method. TGA-DTA test also proved that Ni-CeO2/SBA-15-G almost completely eliminated carbon deposition. The above advantages of the Ni-CeO2/SBA-15-G catalyst may have originated from the complexation of glycine with metal cations and can prevent them from gathering.