In Situ Surface-Enhanced Raman Spectroscopic Evidence on the Origin of Selectivity in CO2 Electrocatalytic Reduction.

The electrocatalytic reduction of CO2 (CO2ER) to liquid fuels is important for solving fossil fuel depletion. However, insufficient insight into the reaction mechanisms renders a lack of effective regulation of liquid product selectivity. Here, in situ surface-enhanced Raman spectroscopy (SERS) empowered by 13C/12C isotope exchange is applied to probing the CO2ER process on nanoporous silver (np-Ag). Direct spectroscopic evidence of the preliminary intermediates, *COOH and *OCO-, indicates that CO2 is coordinated to the catalyst via diverse adsorption modes. Further, the relative Raman intensities of the above intermediates vary notably on np-Ag modified by Cu or Pd, and the liquid product selectivity also changes accordingly. Combined with density functional theory calculations, this study demonstrates that the CO2 adsorption configuration is a critical factor governing the reaction selectivity. Meanwhile, *COOH and *OCO- are key targets in the initial stage regulating liquid product selectivity, which could facilitate future selective catalyst design.

Elevated occupational exposure to chlorinated phosphate esters at a construction materials manufacturing plant.

BACKGROUND: Numerous studies have documented that the general population is widely exposed to organophosphate esters (OPEs), yet studies on the emissions of OPEs in the industrial application processes and their occupational exposure are scarce. The aim of this study was to assess the exposure to OPEs for workers engaged in OPE-retarded construction material manufacturing plant in China. METHOD: Paired dust samples (12 samples each time) from an OPEs retarded building materials manufacturing plant during the plant uptime and downtime have been analyzed for tris(2-chloroethyl)-phosphate (TCEP), tris(2-chloroisopropyl) phosphate (TCPP), and other commonly used OPEs. Moreover, nine OPEs metabolites (mOPEs) in urine samples (n = 42) from fourteen workers who engaged in this plant were also measured. The daily exposure doses to OPEs were estimated from the measured urinary concentrations of corresponding mOPEs. RESULTS: Thirteen out of fourteen studied OPEs (except for tri-n-propyl phosphate, TnPP) were determined in all dust samples from the manufacturing plant, and TCEP and TCPP were the predominant compounds in dust collected from the plant uptime and downtime. Overall, the occupationally exposed population had significantly higher (p < 0.01) urinary levels of mOPE, especially for bis (2-chloroethyl) phosphate (BCEP), relative to the reference population. Workshop workers who directly involved in the production of OPEs treated products had higher OPEs exposure. Risk assessment revealed that cancer risk (1.5 × 10-6-8.5 × 10-4) for all workers was larger than 1 × 10-6 when levels of mOPEs in urine from workers were used for estimating OPEs exposure, revealing moderate to high potential cancer risk to workers from OPEs exposure. CONCLUSION: To our knowledge, this is the first study reporting emissions of OPEs in OPE-treated products manufacturing processes and the potential exposure of the occupationally exposed population. OPEs, especially for TCEP and TCPP, present at elevated levels and pose moderate to high potential health risks to the exposed workers, emphasizing the importance of strengthening occupational exposure prevention in similar industries.

Defect Sites in Ultrathin Pd Nanowires Facilitate the Highly Efficient Electrochemical Hydrodechlorination of Pollutants by H*ads.

Adsorbed atomic H (H*ads) facilitates indirect pathways playing a major role in the electrochemical removal of various priority pollutants. It is crucial to identify the atomic sites responsible for the provision of H*ads. Herein, through a systematic study of the distribution of H*ads on Pd nanocatalysts with different sizes and, more importantly, deliberately controlled relative abundance of surface defects, we uncovered the central role of defects in the provision of H*ads. Specifically, the H*ads generated on Pd in an electrochemical process increased markedly upon introducing defect sites by changing the morphology to ultrathin polycrystalline Pd nanowires (NWs), while dramatically reducing upon decreasing the number of surface defects through an annealing treatment. Benefiting from a proportion of H*ads up to 40% of the total H* species, the Pd NWs showed an electrochemical active surface area normalized rate constant of 13.8 ± 0.8 h-1 m-2, which is 8-9 times higher than its Pd/C counterparts. The pivotal role of defect sites for the generation of H*ads was further verified by blocking such sites with Rh and Pt atoms, while theoretical calculation also confirms that the adsorption energy of H*ads on these sites is much higher than that on the Pd{111} facet.

Au@Pd Bimetallic Nanocatalyst for Carbon-Halogen Bond Cleavage: An Old Story with New Insight into How the Activity of Pd is Influenced by Au.

AuPd bimetallic nanocatalysts exhibit superior catalytic performance in the cleavage of carbon-halogen bonds (C-X) in the hazardous halogenated pollutants. A better understanding of how Au atoms promote the reactivity of Pd sites rather than vaguely interpreting as bimetallic effect and determining which type of Pd sites are necessary for these reactions are crucial factors for the design of atomically precise nanocatalysts that make full use of both the Pd and Au atoms. Herein, we systematically manipulated the coordination number of Pd-Pd, d-orbital occupation state, and the Au-Pd interface of the Pd reactive centers and studied the structure-activity relationship of Au-Pd in the catalyzed cleavage of C-X bonds. It is revealed that Au enhanced the activity of Pd atoms primarily by increasing the occupation state of Pd d-orbitals. Meanwhile, among the Pd sites formed on the Au surface, five to seven contiguous Pd atoms, three or four adjacent Pd atoms, and isolated Pd atoms were found to be the most active in the cleavage of C-Cl, C-Br, and C-I bonds, respectively. Besides, neighboring Au atoms directly contribute to the weakening of the C-Br/C-I bond. This work provides new insight into the rational design of bimetallic metal catalysts with specific catalytic properties.

Tracking the Fate of Surface Plasmon Resonance-Generated Hot Electrons by In Situ SERS Surveying of Catalyzed Reaction.

Plasmonic catalysis is an emerging process that utilizes surface plasmon resonance (SPR) process to harnesses solar energy for the promotion of catalyzed reactions. In most cases, SPR generated hot electrons (HEs) play an indispensable role in this solar-chemical energy shift process. Therefore, understanding the effectiveness of the HEs in promoting chemical reactions, and identifying the key factors that contribute to this utilization efficiency is of profound importance. Herein, the authors outline an in situ surface enhanced Raman spectroscopy protocol to track the fate of HEs. This is based on the unheeded HEs-acceleration nature of the p-nitirothiophenol hydrogenation reaction. By this way, the authors discover that unlike Au@Pd nanostructures which experience a 20-fold increase in rate constant, HEs primary leak to surrounding H+ /O species through Ag pinholes in Ag@Pd. This work sheds light on why Ag is seldom employed as a plasmonic cocatalyst, and provides a new viewpoint to design plasmonic nanocatalysts with efficient light utilization.