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Electrochemical reduction of CO2 is a promising strategy to realize clean energy and a balanced carbon cycle. However, a critical challenge for this approach is to develop effective electrocatalysts with high current density and selectivity. Here, we report the facile synthesis of a highly efficient carbon coated silver (Ag/C) catalyst for CO2 reduction through a simple ultrasonic pyrolysis method. The obtained Ag/C exhibits high CO faradaic efficiency of up to 95% at a high current density of 800 mA cm−2 in 1 M KOH, which is far superior to the performance of state-of-the-art Ag-based catalysts. Mechanistic investigations combined with surface spectroscopic studies reveal that the amorphous carbon shell can boost the CO2 adsorption in the catalytic layer during CO2 electroreduction, favoring the formation of highly active solid–liquid–gas interfacial environments. The findings of this study contribute to the design and synthesis of highly active Ag-based catalysts for industrial-level applications. [ABSTRACT FROM AUTHOR]

Photocatalytic water splitting has been widely studied as a means of converting solar energy into hydrogen as an ideal energy carrier in the future. Systems for photocatalytic water splitting can be divided into one-step excitation and two-step excitation processes. The former uses a single photocatalyst while the latter uses a pair of photocatalysts to separately generate hydrogen and oxygen. Significant progress has been made in each type of photocatalytic water splitting system in recent years, although improving the solar-to-hydrogen energy conversion efficiency and constructing practical technologies remain important tasks. This perspective summarizes recent advances in the field of photocatalytic overall water splitting, with a focus on the design of photocatalysts, co-catalysts and reaction systems. The associated challenges and potential approaches to practical solar hydrogen production via photocatalytic water splitting are also presented. [ABSTRACT FROM AUTHOR]

Obtaining hydrogen energy from photocatalytic water splitting driven by solar energy is a promising strategy to solve the global energy crisis. Herein, by taking the photoinduced activation effects of TiO2, we obtained a Ti3+ self-doped TiO2 (Ti3+–TiO2). In situ characterization revealed that the presence of Ti3+ is attributed to the reduction reaction of Ti4+ on the TiO2 surface under UV light irradiation. The research results prove that the optical properties of TiO2 are modified by the active species Ti3+; the recombination rate of the photogenerated carriers is significantly decreased, and Ti3+–TiO2 exhibits a hydrogen production rate which is 1.7 times superior than that of pristine TiO2. To further enhance the self-activation effect of TiO2, we constructed a type II heterojunction TiO2/UiO-66-NH2 structure to transfer photoexcited electrons to TiO2, which gives a higher concentration and duration of the active species Ti3+. Ti3+–TiO2/UiO-66-NH2 shows improved photocatalytic hydrogen evolution activity with a rate 3.2 times better than that of pristine TiO2 due to the synergistic function of oxygen vacancies and Ti3+. A novel perspective was adopted in this work to observe the dynamic variation of active species and electron transfer pathways during TiO2 photocatalytic reactions. Since Ti3+ is generated on the TiO2in situ, this work could be extended to TiO2-based photocatalysts. [ABSTRACT FROM AUTHOR]

Traditional sensor materials for detecting gaseous and volatile compounds still have relatively low sensitivity and high price, which limits their large-scale applications. It is critical to improve the changes of sensor resistance vs. the amount of adsorbed target gas by promoting the designed surface reaction. Herein, an atomically deposited Ag on tungsten oxide nanoplate (AD-Ag-WO3) sensor is synthesized by a low temperature deposition method to tackle the existing problems. It is found that the AD-Ag-WO3 is very sensitive when exposed to triethylamine (TEA). Meanwhile, the films showed an unexpectedly high response and low operating temperature due to the deposition of the single-atom silver. Among all of the synthesized materials, 0.01 M AD-Ag-WO3 sensors exhibited far superior gas sensing performance (5150 for 50 ppm at 175 °C) to TEA, which is enhanced 50 times compared with that of pure WO3 (110 for 50 ppm at 250 °C). Simultaneously, the AD-Ag-WO3 sensor also showed an extremely low limit of detection (LLD) (1.7 ppb, far superior to that of traditional materials) and an ultrahigh selectivity for TEA. Such an excellent performance can be ascribed to the presence of single-atom Ag. The synthetic method of loading metal single atoms onto gas-sensitive materials can be extended to other similar composite materials, which opens the way for the industrial application of gas-sensitive sensors induced by designed single-atoms. [ABSTRACT FROM AUTHOR]

Sulfur accurate determination plays a vital role in the evaluation of coal quality. In this work, double-pulse laser-induced breakdown (DP-LIBS) in a helium atmosphere was presented and applied in the sulfur concentration quantification of coal. The ablation plasma generated from the sample surface by the first laser (Nd:YAG laser at 1064 nm, 50 mJ per pulse) was re-excited orthogonally by the second laser pulse (Nd:YAG laser at 1064 nm, 120 mJ per pulse). The intensity of sulfur spectral lines has been enhanced with DP-LIBS and the interference from O I 926.6 has been weakened in the helium atmosphere. The calibration curves of S I 921.3 nm, S I 922.8 nm and S I 923.8 nm have been established for 10 coal samples with S concentration ranging from 0.28 wt% to 4.01 wt%. The best result was achieved with R2 = 0.992, LoD = 0.038 wt%, and RMSECV = 0.143 wt%. The overall results adequately demonstrate that DP-LIBS combined with a helium atmosphere has excellent analytical performance for sulfur determination in coal and enormous potential for on-line detection in the coal industry. [ABSTRACT FROM AUTHOR]

Tobacco smoke is a complex mixture consisting of hundreds of toxic and carcinogenic chemicals, which may cause many diseases once inhaled. Among these toxic substances, radioactive and non-radioactive heavy metals present great health concerns to both active and passive smokers. However, conventional methodologies for characterizing heavy metals in smoke require intensive and time-consuming preparation procedures, and thus prevent their on-line applications. We report here a portable laser-induced breakdown spectroscopy (PLIBS) device for on-line detection of radioactive and non-radioactive heavy metals in tobacco smoke with ultra-high sensitivity. Two local cigarette brands were investigated, and a number of heavy metals were detected. In particular, several radioactive metals show very strong atomic emissions, and a limit of detection down to parts per trillion was obtained by single-shot PLIBS. The linear dependencies of their spectral intensities on the smoke concentrations were revealed, suggesting that the PLIBS is a promising tool for high-throughput and quantitative analysis of heavy metals in tobacco smoke. Tobacco emission dynamics were also investigated, and the results suggest the potential applications of the PLIBS in smoke risk assessment. [ABSTRACT FROM AUTHOR]