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The development of robust and efficient electrocatalysts for use in fuel cells and metal–air batteries has garnered a great deal of interest due to the quest for clean and renewable energy sources. In this paper, a promising Co-doped Pr0.5Ba0.4Ca0.1Fe1-xCoxO3-δ (x = 0, 0.2, 0.4, 0.6, 0.8; denoted as PBCFC-x, x = 0, 2, 4, 6, 8) with enhanced durability and electrocatalytic ORR/OER activity for zinc–air battery cathode catalysts is presented. Particularly, PBCFC-6 exhibits the best bifunctional catalytic activity in alkaline media among several materials, according to research using the RDE. The zinc–air battery with PBCFC-6 as the cathode catalyst delivered the smallest discharge–charge voltage difference at the current density of 10 mA·cm−2 and only increased by 0.031 V after 220 cycles (220 h), demonstrating its superior bifunctional catalytic activity and durability. The optimized electrochemical performance of both OER and ORR as well as stability in zinc–air batteries might result from the higher electrical conductivity, increasing concentration of adsorbed oxygen, and the greater proportion of Fe4+ (t2g3eg1) with optimal electron occupancy, owing to the partial replacement of Fe with Co. [ABSTRACT FROM AUTHOR]

• The intrinsic activity for OER is enhanced after Sr doping. • Partial substitution of Fe with Mn can transform the reduction of O 2 to H 2 O from a two-electron reduction pathway to a four-electron dominated pathway. • Sr and Mn co-doped Pr 0.6 Sr 0.4 Fe 0.8 Mn 0.2 O 3-δ exhibits excellent bifunctional activity and stability for zinc-air batteries. Reasonable design of perovskite oxides with outstanding and durable oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) performance is of vital importance to enhancing the performance of zinc-air batteries. In this paper, PrFeO 3-δ and a series of Sr and Mn co-doped Pr 0.6 Sr 0.4 Fe 1-x Mn x O 3-δ (x = 0, 0.2 and 0.4) perovskite materials were successfully prepared via a citrate-nitrate combustion process and used in rechargeable zinc-air batteries as bifunctional catalysts. The rotating disk electrode technique demonstrated the bifunctional catalytic activity of several materials in an alkaline medium increase in the order of Pr 0.6 Sr 0.4 Fe 0.8 Mn 0.2 O 3-δ (PSFM-82), Pr 0.6 Sr 0.4 Fe 0.6 Mn 0.4 O 3-δ (PSFM-64), Pr 0.6 Sr 0.4 FeO 3-δ (PSFM-0) and PrFeO 3-δ (PFO). Compare to PFO, PSFM-82 displayed a greater peak power density (56.3 mW·cm−2) as an oxygen electrode catalyst for zinc-air batteries. The smaller discharge-charge cycle difference (1.03 V) of PSFM-82 after 135 cycles (135 h) at the current density of 10 mA·cm−2 also demonstrates its notably bifunctional activity and excellent cycling stability than that of PFO. The enhanced electrocatalytic property of both ORR and OER could be owing to the greater specific surface area, higher electrical conductivity and the coexistence of Fe4+ and Mn3+ ions with optimal electron filling caused by the partial substitution of Pr with Sr and Fe with Mn. [ABSTRACT FROM AUTHOR]

Titania-supported gold nanoparticles were prepared by using the deposition-precipitation method, followed by reduction under a hydrogen flow. The catalytic activity of these as-prepared catalysts was explored in the oxidation of cellobiose to gluconic acid with molecular oxygen, and the properties of these catalysts were examined by using XRD, TEM, temperature-programmed desorption of NH3, energy-dispersive X-ray spectroscopy, UV/Vis, and X-ray photoemission spectroscopy (XPS). The catalyst sample reduced at high temperature demonstrated an excellent catalytic activity in the oxidation of cellobiose. The characterization results revealed the strong metal-support interaction between the gold nanoparticles and titania support. Hydrogen reduction at higher temperatures (usually >600 °C) plays a vital role in affording a unique interface between gold nanoparticles and titania support surfaces, which thus improves the catalytic activity of gold/titania by fine-tuning both the electronic and structural properties of the gold nanoparticles and titania support. [ABSTRACT FROM AUTHOR]

• A bifunctional catalyst with two active sites of controllable intimacy is synthesized. • The proximity between two active sites is regulated with nanometer precision. • The proximity has significant effect on the catalytic activity and product selectivity. • A kinetic study reveals a synergy of solvent composition and catalytic species. • The study provides a deep understanding on the cascade catalysis in solvent systems. For responding to the rapidly increasing trend of research on biorefinery, a diverse range of furans derived from biomass emerge as versatile platform chemicals for a spectrum of pharmaceutical applications. However, it is a formidable challenge to transform biomass feedstock into valuable furan-based chemicals via complicated cascade reactions. Here, we develop a bifunctional reduced graphene oxide (rGO)-supported catalyst with two controllably intimate active sites (namely Ru species and sulfonic acid groups, respectively) on the graphene sheets. The structural and morphological evolution of the catalyst is characterized by FTIR, Raman, XPS, XRD, SEM, and HR-TEM. This catalyst is employed in a biphasic solvent system for the one-pot conversion of fructose to 2,5-diformyfuran (DFF) which is a high-value pharmaceutical intermediate. We demonstrate that the nanoscale proximity of two active sites and the solvent composition are crucial to the catalytic activity and DFF selectivity in the cascade catalysis. The spatial organization of Ru species and sulfonic acid groups reveals an optimized inter-site distance of 12.5 ± 2.2 nm for the high catalytic activity. A solvent-influenced kinetic model is established and accurately elaborates the regulatory role of toluene (as the co-solvent) on the reaction pathways. More importantly, this bifunctional catalyst can be recycled for 4 times without significant loss of catalytic activity. Taken together, a deep understanding is highlighted which provides clues on the optimization of multifunctional catalysts and the choice of solvent system in the cascade catalysis which is a general unit operation in chemical engineering processes. [ABSTRACT FROM AUTHOR]