N,S co-doped SnO2 catalysts in gas-liquid interface dielectric barrier discharge for formate formation via CO2 reduction

N,S co-doped SnO2 were deposited on MWNTs/sponge to prepare a series of related N-S-SnO2/MWNTs/sponges for the reduction of CO2 by dielectric barrier discharge (DBD). With optimizing the composition, the N-S-SnO2/MWNTs/sponge (N:S:Sn = 1:0.2:1) achieves higher yields of formate (4791.40 μmol/L) and formaldehyde (66.11 μmol/L) after 60 min. The structural properties and DFT calculations reveal that, the S doped increased oxygen-containing functional groups on catalysts surface, thus the nonmetallic N and S modified Sn based catalysts affected the adsorption sites and reduced the reaction energy barrier of CO2 on the catalyst surface in order to promote energy utilization of DBD system for CO2 catalytic reduction. In addition, different types and concentrations of seawater ions such as K+, Na+, Ca2+, Mg2+, Cl- and SO42- affected on the formation of formic acid and formaldehyde during discharge, which showed that DBD catalysis technology was advanced used for CO2 capture and storage in the ocean. [Display omitted] •Suspended N-S-SnO2 compound was used for CO2RR by gas-liquid DBD technology.•Yields of total formate and formaldehyde reached ∼5.5 mmol L−1 h−1 for CO2RR.•N,S co-doping SnO2 has a higher oxygen vacancy ratio than N doping SnO2.•S doping on N-SnO2 changed surface structure and decreased CO2 adsorption energy.•High ion concentrations in simulated seawater hindered mass transfer for CO2RR.