Abstract Developing Pd-based catalysts for formic acid (HCOOH) dehydrogenation is of great significance to the advancement of renewable hydrogen utilization. However, traditional Pd surfaces typically display symmetrical electronic and geometrical configurations that suffer from both selectivity issues and CO poisoning phenomena, deteriorating their long-term HCOOH dehydrogenation performance. In this study, we report a bismuth–palladium (BiPd) alloy catalyst with asymmetric electronic and geometric Pd sites that achieved an exceptional H2-evolving turnover frequency (5893.7 h–1) of HCOOH dehydrogenation while maintaining over 96% catalytic activities spanning consecutive 15-round experiments. High-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) and synchrotron X-ray absorption spectroscopy (XAS) characterizations verified the successful construction of BiPd alloys and that Bi components desymmetrized the electronic configuration of Pd sites toward the thermodynamically favored HCOOH dehydrogenation pathway for H2 evolution. On the other hand, in situ diffuse reflectance infrared fourier transform spectroscopy (DRIFTS) and kinetic isotope effect experiments combined with density functional theory (DFT) calculations collectively demonstrated that Bi also diluted Pd ensembles, and the resulting asymmetric Pd architectures reduced the diversity of *CO adsorption configurations on the surface of BiPd alloys, effectively mitigating CO poisoning. This work underscores the critical role of alloying engineering in designing Pd-based catalysts for practically implementing sustainable hydrogen release from liquid organic hydrogen carriers.
Abstract The production of jet-fuel-grade butyl-butyrate from butanol has been investigated using a series of NNN pincer-Ru catalysts. Notably, a majority of the considered pincer-Ru complexes, excluding the Ru precursors, demonstrated good activity toward the upgradation of n-butanol to butyl-butyrate. In particular, in the presence of 10 mol % of KOtBu at 160 °C, the complex [(MeBim2NNN)RuCl2(PPh3)2]Cl (1 mol %) based on the 2,6-bis(benzimidazole-2-yl)pyridine ligand demonstrated very high activity, giving up to 90% yield of butyl-butyrate starting from n-butanol after 72 h of reaction. The reaction proceeded with favorable green metrics (97.3% atom economy, 87.6% atom efficiency, 100% carbon efficiency, and 87% reaction mass efficiency). On the other hand, the complex ((p-OMe-C6H4)2NNN)RuCl2PPh3 based on the bis(imino)pyridine ligand exhibited the lowest activity and gave 40% yield of butyl-butyrate. Mechanistic studies reveal that the catalytic transformation of n-butanol to butyl-butyrate has a first-order dependence of the initial rate on the concentration of [(MeBim2NNN)RuCl2(PPh3)2]Cl, while a second-order dependence on the concentration of n-butanol is observed. The catalytically active species is homogeneous with a well-defined molecular nature; a few of these molecular species, including the resting-state (MeBim2NNN)RuHCl (experimentally trapped as its PPh3 adduct), have been identified by HRMS and NMR analysis. While the observed KIEs of 1.1 and 2.4 in experiments with C4H9OD and C4D9OD, respectively, are suggestive of the involvement of a rate-determining C–H bond activation, the corresponding activation Gibbs free energy is experimentally determined to be 25.3 kcal/mol by Eyring plot analysis. DFT studies further fortify the experimental observations while suggesting that the rate-determining step (RDS) involves the β-hydride elimination from hemiacetal coordinated pincer-Ru species with a barrier of 25.2 kcal/mol leading to the extrusion of butyl-butyrate along with the formation of the resting-state (RS) species (MeBim2NNN)RuHCl. In stark contrast, the catalysis with ((p-OMe-C6H4)2NNN)RuCl2PPh3, which is the least active among the considered catalysts, is kinetically unfavorable (ΔG160‡ = 34.6 kcal/mol). This study not only provides a convenient high-yield synthetic protocol to jet-fuel-grade butyl-butyrate via pincer-Ru-catalyzed dehydrogenative coupling of n-butanol but also provides key mechanistic insights that could leverage the global efforts in designing effective dehydrogenative esterification catalysts for the upgradation of alcohols.
Abstract Solar-driven photocatalytic water splitting represents a promising route for sustainable hydrogen production. However, the practical application of single-component photocatalysts is severely constrained by rapid bulk charge-carrier recombination. CdZnS (CZS) solid solutions have garnered significant interest as visible-light-active photocatalysts due to their compositionally tunable band structures. However, photocorrosion and sluggish interfacial charge transfer critically hinder their practical application. To address these limitations, we herein report an S-scheme heterojunction photocatalyst (Ni-CZS/MW), constructed by integrating Ni-doped CZS (Ni-CZS) with MnWO4 (MW). Ni-doping markedly diminishes the work function of Ni-CZS, creating a substantial work-function difference with MW that induces interfacial charge asymmetry. An internal electric field generated by the intimate contact at the Ni-CZS/MW interface directs the migration of photoexcited electrons from MW to Ni-CZS through an S-scheme charge-transfer pathway, thereby significantly enhancing charge-carrier separation efficiency. Under visible-light irradiation, the optimized Ni-CZS/MW heterostructure produces 882 μmol of hydrogen. Furthermore, this catalyst demonstrates a strong ability to catalytically reform microplastics, the hybrid system simultaneously generates 331 μmol of hydrogen and upcycles PLA into pyruvic acid (PA). Collectively, these findings elucidate the synergistic roles of S-scheme heterojunction engineering and Ni-doping in modulating charge-carrier dynamics, and provide a strategic framework for designing photocatalysts tailored for plastic waste valorization.
Abstract The high production cost of polyhydroxybutyrate (PHB) remains a major barrier to its commercial application. Therefore, it is imperative to develop processes that combine low-cost lignocellulose feedstocks with robust microbial strains. In this study, a fermentation process with an emerging microbial strain was evaluated, possessing the potential to significantly accentuate the kinetics of cell growth and product accumulation. Genome annotation of the strain Halomonas hydrothermalis Slthf2 revealed a complete acyl-CoA-dependent PHB biosynthetic pathway and four full-length putative PhaA homologues, supporting the genetic capacity of H. hydrothermalis Slthf2 for PHB biosynthesis. Response surface methodology based on the Box–Behnken design was used to optimize pH, steam-exploded corn stover (SECS) concentration, and temperature. Based on the optimized conditions, a fed-batch simultaneous saccharification and fermentation (SSF) process with sequential SECS feeding was developed to promote cellulose conversion and PHB accumulation. The optimized process achieved a maximum PHB concentration of 15.1 g/L, corresponding to a PHB content as high as 67.7%. Due to its environmental adaptability and inhibitor tolerance, H. hydrothermalis was identified as an ideal PHB producer in the complex lignocellulosic reaction system containing various inhibitors. This work demonstrates a more sustainable and process-optimized technology for PHB production from lignocellulosic biomass by H. hydrothermalis.
Abstract Sugarcane bagasse (SCB) is an abundant lignocellulosic by-product with high potential for the sustainable production of xylo-oligosaccharides (XOS) and cello-oligosaccharides (COS), compounds with reported functional and prebiotic applications. This study presents an integrated fractionation and hydrolysis approach to produce XOS and COS from SCB using chemical treatments and commercial enzymes. SCB was fractionated via hydrogen peroxide-acetic acid (HPAA) pretreatment followed by alkaline peroxide extraction (APE), yielding cellulosic and hemicellulosic fractions with 78.3% cellulose and 69.3% xylan, respectively. X-ray diffraction and ATR-FTIR confirmed selective lignin removal and polysaccharide enrichment. Enzymatic hydrolysis produced XOS (25.5% yield, 6 h) and COS (49.8% yield, 12 h), corresponding to an estimated production potential of 26.9 kg XOS and 203.7 kg COS per ton of raw SCB. The process exhibited a water-excluded process mass intensity (PMI) of 249.2 and an E-factor of 248.2, driven mainly by ethanol consumption; a sensitivity analysis showed that ethanol recovery efficiencies of 70–95% could lower PMI to 46–99, a 60–85% reduction. These findings demonstrate the technical feasibility of producing high-value oligosaccharides from agro-industrial waste and highlight solvent recovery as a key lever toward a more sustainable biorefinery process.
