In this study, graphitized carbon nitride photocatalysts were successfully prepared by using the desulfurized waste liquid extracting salt from coking plants. The NO x removal efficiency of g-C 3 N 4 synthesized using ammonium thiocyanate (NH 4 SCN), ammonium thiosulfate ((NH 4 ) 2 S 2 O 3 ) and ammonium sulfate ((NH 4 ) 2 SO 4 ) with different mass ratios were evaluated. The results showed that due to the addition of (NH 4 ) 2 S 2 O 3 and (NH 4 ) 2 SO 4 a large amount of sulfur-containing gas was released during pyrolysis, which significantly increased the specific surface area and pore volume of the photocatalysts. The release of sulfur-containing gas also resulted in the incorporation of sulfur, and due to this doping process the band gap of the photocatalyst was widened to 2.94 eV, thus enhancing its visible light response. C vacancies were formed in the hepazine ring, which increased the electron density around the N–(C) 3 bridge bond and formed an electron trapping center, thus inhibiting the recombination of charge carriers. The photocatalysts had increased O 2 adsorption capacity and increased number of amino groups on their surface. This facilitated the rapid generation and consumption of reactive oxygen species, inhibited the accumulation of NO 2 on the surface, reduced the production of NO 2 , thus improving the NO x removal efficiency of the photocatalysts. The principle of using “waste for waste control” was achieved, and a new method for nitrogen oxide removal was provided.
Weirui Chen,Siyou Fu,Xukai Li,Jing Wang,Xunan Ning,Liying Bin,Ping Li,Bing Tang,Laisheng Li
Photocatalytic ozonation (PCO) was a novel water treatment method, but the low photo-generated electron ( e - ) utilization and ambiguous ROS formation mechanism restrained its performance. Herein, C vacancy and F co-decorated g-C 3 N 4 (FCN_Cv) was designed to accelerate the PCO performance with sodium p -perfluorinated nonoxybenzenesulfonate (OBS) acting as model pollutant. Comparative characterizations revealed that FCN_Cv remained the inherent structure of g-C 3 N 4 (BCN), and had an enhanced conduction band potential, narrower band gap and longer e - lifetime. FCN_Cv exhibited the greater activity over BCN, with 99.3 % OBS removal in 30 min but only 78.3 % for BCN during PCO process. •OH was the main ROS for degrading OBS. The greater •OH yield was obtained by FCN_Cv PCO process because of the increase of e - utilization. On one hand, the two electrons reduction of O 2 into H 2 O 2 on FCN_Cv was accelerated, which triggered the peroxone reaction between photogenerated-H 2 O 2 and O 3 . On the other hand, the direct one electron reduction of O 3 by e - also accounted for •OH generation. 17 kinds of intermediates were detected and the OBS degradation routes were inferred, which was involved with hydroxylation, C-O cleavage and aromatic ring opening reactions. Overall, this study demonstrated the feasibility of decorating F element and C vacancy on g-C 3 N 4 in enhancing e - utilization and •OH generation during PCO process as well as deepened the understanding of fate of OBS in PCO process.
Rong Wang,Chuan Gao,Haiwei Su,Zhen Chen,Junhua Li,Yue Peng
Proton–electron transfer (PET) processes play a pivotal role in numerous electrochemical reactions; yet, effectively harnessing them remains a formidable challenge. Consequently, unveiling the PET pathway is imperative to elucidate the factors influencing the efficiency and selectivity of small molecule electrochemical conversion. In this study, a Zn–NC model catalyst with N and C vacancies was synthesized using a hydriding method to investigate the universal impact of PET on CO2 electroreduction. The introduction of N vacancies induced the formation of a distinctive Zn–N3 topological structure and atomically populated Znδ+ sites with lower valence states, thereby facilitating the cleavage of the C═O bonds. Conversely, C vacancies led to the formation of stable C–H bonds and tuned the rate of dissociation of H2O to H*. In comparison to sequential proton–electron transfer, concerted proton–electron transfer significantly enhanced the formation of *COOH species, a critical step in the CO2 reduction process on a Zn-enhanced N-doped carbon catalyst. The catalyst exhibited a remarkable 96% CO Faradaic efficiency at −0.36 V vs RHE. This research contributes to the ongoing endeavors to unlock the full potential of concerted proton–electron transfer in electrochemical synthesis and its application in sustainable energy and environmental solutions.
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