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The oxidative coupling of methane to higher hydrocarbons offers a promising autothermal approach for direct methane conversion, but its progress has been hindered by yield limitations, high temperature requirements, and performance penalties at practical methane partial pressures (~1 atm). In this study, we report a class of Li₂CO₃-coated mixed rare earth oxides as highly effective redox catalysts for oxidative coupling of methane under a chemical looping scheme. This catalyst achieves a single-pass C₂₊yield up to 30.6%, demonstrating stable performance at 700 °C and methane partial pressures up to 1.4 atm. In-situ characterizations and quantum chemistry calculations provide insights into the distinct roles of the mixed oxide core and Li₂CO₃shell, as well as the interplay between the Pr oxidation state and active peroxide formation upon Li₂CO₃coating. Furthermore, we establish a generalized correlation between Pr⁴⁺content in the mixed lanthanide oxide and hydrocarbons yield, offering a valuable optimization strategy for this class of oxidative coupling of methane redox catalysts.

 

Core-shell–structured “perovskite oxide@molten LiBr” redox catalyst anaerobically converts n -butane into butadiene. 

The current study reports AxA’1-xByB’1-yO3-𝛿 perovskite redox catalysts (RCs) for CO2-splitting and methane partial oxidation (POx) in a cyclic redox scheme. Strontium (Sr) and iron (Fe) were chosen as A and B site elements with A’ being lanthanum (La), samarium (Sm) or yttrium (Y), and B’ being manganese (Mn), or titanium (Ti) to tailor their equilibrium oxygen partial pressures (P_(O_2 ) s) for CO2-splitting and methane partial oxidation. DFT calculations were performed for predictive optimization of the oxide materials whereas experimental investigation confirmed the DFT predicted redox performance. The redox kinetics of the RCs improved significantly by 1 wt.% ruthenium (Ru) impregnation without affecting their redox thermodynamics. Ru impregnated LaFe0.375Mn0.625O3 (A=0, A’=La, B=Fe, and B’=Mn) was the most promising RC in terms of its superior redox performance (CH4/CO2 conversion >90% and CO selectivity~ 95%) at 800oC. Long-term redox testing over Ru impregnated LaFe0.375Mn0.625O3 indicated stable performance during the first 30 cycles following with a ~25% decrease in the activity during the last 70 cycles. Air treatment was effective to reactivate the redox catalyst. Detailed characterizations revealed the underlying mechanism for redox catalyst deactivation and reactivation. This study not only validated a DFT guided mixed oxide design strategy for CO2 utilization but also provides potentially effective approaches to enhance redox kinetics as well as long-term redox catalyst performance. 

Integration of carbon dioxide capture from flue gas with dry reforming of CH 4 represents an attractive approach for CO 2 utilization. The selection of a suitable bifunctional material serving as a catalyst/sorbent is the key. This paper reports Ni decorated and CeO x -stabilized SrO (SrCe 0.5 Ni 0.5 ) as a multi-functional, phase transition catalytic sorbent material. The effect of CeO x on the morphology, structure, decarbonation reactivity, and cycling stability of the catalytic sorbent was determined with TEM-EDX, XRD, in situ XRD, CH 4 -TPR and TGA. Cyclic process tests were conducted in a packed bed reactor. The results indicate that large Ni clusters were present on the surface of the SrNi sorbent, and the addition of CeO 2 promoted even distribution of Ni on the surface. Moreover, the Ce–Sr interaction promoted a complex carbonation/decarbonation phase-transition, i.e. SrCO 3 + CeO 2 ↔ Sr 2 CeO 4 + CO 2 as opposed to the conventional, simple carbonation/decarbonation cycles ( e.g. SrCO 3 ↔ SrO + CO 2 ). This double replacement crystalline phase transition mechanism not only adjusts the carbonation/calcination thermodynamics to facilitate SrCO 3 decomposition at relatively low temperatures but also inhibits sorbent sintering. As a result, excellent activity and stability were observed with up to 91% CH 4 conversion, >72% CO 2 capture efficiency and ∼100% residual O 2 capture efficiency from flue gas by utilizing the CeO 2 ↔ Ce 2 O 3 redox transition. This renders an intensified process with zero coke deposition. Moreover, the SLDRM with SrCe 0.5 Ni 0.5 has the flexibility to produce concentrated CO via CO 2 -splitting while co-producing a syngas with tunable H 2 /CO ratios. 

Alkaline fuel cells enable the use of earth-abundant elements to replace Pt but are hindered by the sluggish kinetics of the hydrogen oxidation reaction (HOR) in alkaline media. Precious metal–free HOR electrocatalysts need to overcome two major challenges: their low intrinsic activity from too strong a hydrogen-binding energy and poor durability due to rapid passivation from metal oxide formation. Here, we designed a Ni-based electrocatalyst with a 2-nm nitrogen-doped carbon shell (Ni@CN x ) that serves as a protection layer and significantly enhances HOR kinetics. A Ni@CN x anode, paired with a Co−Mn spinel cathode, exhibited a record peak power density of over 200 mW/cm 2 in a completely precious metal–free alkaline membrane fuel cell. Ni@CN x exhibited superior durability when compared to a Ni nanoparticle catalyst due to the enhanced oxidation resistance provided by the CN x layer. Density functional theory calculations suggest that graphitic carbon layers on the surface of the Ni nanoparticles lower the H binding energy to Ni, bringing it closer to the previously predicted value for optimal HOR activity, and single Ni atoms anchored to pyridinic or pyrrolic N defects of graphene can serve as the HOR active sites. The strategy described here marks a milestone in electrocatalyst design for low-cost hydrogen fuel cells and other energy technologies with completely precious metal–free electrocatalysts. 

Styrene is an important commodity chemical that is highly energy and CO₂intensive to produce. We report a redox oxidative dehydrogenation (redox-ODH) strategy to efficiently produce styrene. Facilitated by a multifunctional (Ca/Mn)_1−xO@KFeO₂core-shell redox catalyst which acts as (i) a heterogeneous catalyst, (ii) an oxygen separation agent, and (iii) a selective hydrogen combustion material, redox-ODH auto-thermally converts ethylbenzene to styrene with up to 97% single-pass conversion and >94% selectivity. This represents a 72% yield increase compared to commercial dehydrogenation on a relative basis, leading to 82% energy savings and 79% CO₂emission reduction. The redox catalyst is composed of a catalytically active KFeO₂shell and a (Ca/Mn)_1−xO core for reversible lattice oxygen storage and donation. The lattice oxygen donation from (Ca/Mn)_1−xO sacrificially stabilizes Fe³⁺in the shell to maintain high catalytic activity and coke resistance. From a practical standpoint, the redox catalyst exhibits excellent long-term performance under industrially compatible conditions.