Precious Metal Doped Ni–Mg/Ceria–Zirconia Catalysts for Methane Conversion to Syngas by Low Temperature Bi-reforming

Enhanced chemical looping CO2 conversion activity and thermal stability of perovskite LaCo1-xAlxO3 by Al substitution

The reverse water-gas shift chemical looping (RWGS-CL) process that utilizes redox reactions of metal oxides is promising for converting CO2 to CO at low temperatures. Metal oxides with perovskite structures, particularly, perovskite LaCoO3 are promising frameworks for designing RWGS-CL materials as they can often release oxygen atoms topotactically to form oxygen vacancies. In this study, solid solutions of perovskite LaCo1-xAlxO3 (0 ≤ x ≤ 1), which exhibited high CO production capability and thermal stability under the RWGS-CL process, were developed. Al-substituted LaCo0.5Al0.5O3 (x = 0.5) exhibited a 4.1 times higher CO production rate (2.97 × 10-4 CO mol g-1 min-1) than that of LaCoO3 (x = 0; 0.73 × 10-4 CO mol g-1 min-1). Diffuse reflectance infrared Fourier transform spectroscopy studies suggested that an increase in CO2 adsorption sites produced by the coexistence of Al and Co was responsible for the enhancement of CO production rate. Furthermore, LaCo0.5Al0.5O3 maintained its perovskite structure during the RWGS-CL process at 500 °C without significant decomposition, whereas LaCoO3 decomposed into La2O3 and Co0. In situ X-ray diffraction study revealed that the high thermal stability was attributed to the suppression of phase transition into a brownmillerite structure with ordered oxygen vacancies. These findings provide a critical design approach for the industrial application of perovskite oxides in the RWGS-CL processes.

Investigation of catalytic methane oxidation over Ag/Co2MOx (M = Co, Ni, Cu) catalysts with varying interfacial electron transfer

Atom-doped Co3O4 catalysts loaded with Ag were examined as cost-effective catalysts for methane oxidation. The synthesized Ag/Co2NiOx catalysts exhibited distinctive surface characteristics in contrast with Ag/Co3O4 and Ag/Co2CuOx catalysts prepared using a similar method. Characterization results unveiled that Ag/Co2NiOx featured a higher presence of active surface oxygen species, lattice defects, a larger surface area, and enhanced reducibility. A methane oxidation catalytic performance followed the sequence: Ag/Co2NiOx > Ag/Co3O4 > Ag/Co2CuOx. The investigation delved into methane degradation pathways on the surfaces of three catalysts, examining their behavior under both aerobic and anaerobic atmospheres through in-situ DRIFTS analysis. Furthermore, introducing Ag showed a marked positive effect on Co-Ni mixed oxide, inducing electron transfer and a more active electron system, whereas it exhibited an inverse impact within the surface of Co-Cu mixed oxide. This work provides innovative perspectives on the development of forthcoming environmental catalysts.

Biogas Reforming to Syngas: A Review

Interest in novel uses of biogas has increased recently due to concerns about climate change and greater emphasis on renewable energy sources. Although biogas is frequently used in low-value applications such as heating and fuel in engines or even just flared, reforming is an emerging strategy for converting biogas to syngas, which could then be used to obtain high-value-added liquid fuels and chemicals. Interest also exists due to the role of dry, bi-, and tri-reforming in the capture and utilization of CO2. New research efforts have explored efficient and effective reforming catalysts, as specifically applied to biogas. In this paper, we review recent developments in dry, bi-, and tri-reforming, where the CO2 in biogas is used as an oxidant/partial oxidant. The synthesis, characterization, lifetime, deactivation, and regeneration of candidate reforming catalysts are discussed in detail. The thermodynamic limitation and techno-economics of biogas conversion are also discussed.

Intrinsically strained noble metal-free oxynitrides for solar photoreduction of CO2

Metal oxynitrides show promising activity for photocatalytic solar water splitting and CO₂ reduction under solar irradiance. Precise control of cation ratios in oxynitrides is an inevitable challenge that needs to be overcome for achieving effective band gap tuning. Here we report the density functional theory-based calculations for the intricate structure-function relationships of Zn-Ga based oxynitrides and correlate the results with the experimental parameters. Crucial material property descriptors such as elemental composition, intrinsic lattice strain, and vacancy defects were exploited during the synthesis to achieve stable oxynitride photocatalysts that demonstrated CO₂ conversion to CO under simulated solar light, without any noble metal impregnation. The highest CO production rate surpassed that of TiO₂ under the same conditions. This work inspires future research on oxynitride materials with tailored optical properties and sustainable photocatalytic activity which enables their large scale applications.