Search

Photocatalytic carbon dioxide (CO2) conversion is a promising technology to address the greenhouse effect and energy shortage problems by utilizing the inexhausted solar energy. However, the over-reliance on metal-based photocatalysts hampers its long-term application. Here, a series of Earth-abundant natural biomass-derived heteroatom-doped carbonaceous photocatalysts prepared via a sulfuric-acid-assisted carbonization method are developed to convert the CO2 waste into the valuable carbon monoxide (CO) fuel. On account of visible-light-harvesting, large CO2 uptake, efficient charge separation and abundant defects, green catalysts such as the carbonized konjac biomass (CKB) exhibit a superior visible-light-driven CO formation of 115 μmol g−1 h−1 without using any co-catalyst or sacrificial reagent. The versatility of the synthetic approach developed is verified by preparing a series of carbonaceous photocatalysts derived from various Earth-abundant natural biomass precursors including crops, plants, and agricultural waste. The results show that they all perform appreciable photocatalytic CO2-to-CO conversion. This study provides a general method for designing cheap, high-performance, sustainable, and metal-free photocatalysts using natural biomass, which makes the large-scale practical use feasible and helps achieve a closed-loop carbon cycle. [ABSTRACT FROM AUTHOR]

Elemental Ag 0 is well known for its remarkable catalytic and antibacterial properties, thus the regeneration of valuable Ag 0 metal from Ag + wastewater is of great significance. In this study, a novel polyethylenimine (PEI) modified potassium tungsten oxide (N-K 2 W 4 O 13 ) adsorbent was prepared for Ag + removal and reduction to Ag 0 using glutaraldehyde as crosslinking agent. XPS and FT-IR spectra verified PEI successfully anchored on the surface O and W atoms of K 2 W 4 O 13 through aldehyde bridges. The content of PEI in N-K 2 W 4 O 13 was calculated as 8.74wt% by TG curve. A heterogeneous PEI coating was observed in the SEM and TEM images. The N-K 2 W 4 O 13 exhibited larger Ag + uptake (48.25mg/g) than the raw K 2 W 4 O 13 (42.50mg/g) though required a longer equilibrium time. This was due to the combined results of strong chelation and weak electrostatic repulsion that meanwhile occurring on the positive-charged surface of N-K 2 W 4 O 13 . The maximum Ag + uptake on N-K 2 W 4 O 13 was 72.5mg/g, which was larger than many of the reported adsorbents. Furthermore, the prepared N-K 2 W 4 O 13 displayed good anti-interference toward background ions (Na + , K + ) and hold a stable Ag + removal (>95%) after five runs of recycling tests. The mechanism studies elucidated that NH/N groups from the PEI modified N-K 2 W 4 O 13 mainly accounted for the Ag + adsorption and Ag 0 recovery in the adsorption-reduction process. Ion-exchange between Ag + and K + from the N-K 2 W 4 O 13 lattice also occurred. This work provided a facile method to synthesize a promising adsorbent for Ag + wastewater remediation and valuable Ag 0 recovery., (Copyright © 2019. Published by Elsevier B.V.)