Experimental Evidence of CO₂ Photoreduction Activity of SnO₂ Nanoparticles

Abstract

Tin dioxide (SnO2) has intrinsic characteristics that do not favor its photocatalytic activity. However, we evidenced that surface modification can positively influence its performance for CO2 photoreduction in the gas phase. The hydroxylation of the SnO2 surface played a role in the CO2 affinity decreasing its reduction potential. The results showed that a certain selectivity for methane (CH4), carbon monoxide (CO), and ethylene (C2H4) is related to different SnO2 hydrothermal annealing. The best performance was seen for SnO2 annealed at 150 °C, with a production of 20.4 μmol g−1 for CH4 and 16.45 μmol g−1 for CO, while for SnO2 at 200 °C the system produced more C2H4, probably due to a decrease of surface −OH groups.

Creation of SnxNb1−xO2 solid solution through heavy Nb-doping in SnO2 to boost its photocatalytic CO2 reduction to C2+ products under simulated solar illumination

“…The photocatalytic CO 2 reduction products by both samples under the simulated solar illumination were found to be liquid products of CH 3 OH, CH 3 CHO, and C 2 H 5 OH, while no gas product like CO or CH 4 was found. This observation was quite different from the previous reports on the photocatalytic CO 2 reduction by SnO 2 -based photocatalysts to mainly produce CO and CH 4 [33][34][35][36][37][38].…”

“…It could be seen that, the pristine SnO 2 sample had better or similar photocatalytic CO 2 reduction performances, compared with these SnO 2 -based photocatalysts reported, while that of the Sn x Nb 1−x O 2 solid solution sample was over one magnitude higher. Furthermore, the production rate of C 2+ products by the Sn x Nb 1−x O 2 solid solution sample was much higher than various photocatalysts previously reported in pieces of literature [33][34][35][36][37][38], when no sacrificial agent was used during the photocatalytic CO 2 reduction.…”

“…Due to its environmental friendliness, non-toxicity, relatively low cost, and high surface activity, SnO 2 had been extensively explored for various technical applications, including photocatalysts [29], gas sensors [30], dye-sensitized solar cells [31], and supercapacitors [32]. It had been found that SnO 2 [33] and its composites with other photocatalysts like g-C 3 N 4 [34,35], Fe 2 O 3 [36], BiVO 4 [37], or MoS 2 [38] could photocatalytically reduce CO 2 . However, their photocatalytic CO 2 reduction efficiencies were generally low, and only one-carbon (C 1 ) products (mostly CO and CH 4 ) were reported, while multi-carbon (C 2+ ) products are more attractive due to their higher energy density, easier processing and transportation, and better economical values for the industrial application [39].…”

Effect of the oxidation state and morphology of SnOx-based electrocatalysts on the CO2 reduction reaction

“…SnO (PDF2: 01-172-1012) exhibited small peaks due to the small amount in the carbon fiber (18 mg); however, its characteristic peaks related to the plane (101) could be observed. Microsized SnO 2 exhibited all peaks in a well-defined way; on the other hand, as expected, nanometric SnO 2 exhibited small and broad peaks due to its small particle size [33]. In addition, the main peak from SnO 2 , i.e., the (101) plane was overlapped by a carbon fiber peak of about 26º.…”

“…The mixture was dried in a fume hood and then deposited to the carbon fiber electrode (area of 8 cm 2 ) by means of brushing. The electrodes were then cured at 80 °C for 1 h. Three different SnO x -based materials were evaluated: (i) microsized SnO 2 (99.9%, Sigma-Aldrich); (ii) microsized SnO (99.99%, Sigma-Aldrich); and (iii) nanosized SnO 2 that was prepared by means of hydrothermal treatment, as described elsewhere [33]. In detail, 0.564 g of SnCl 2 .2H 2 O (Sigma-Aldrich) was dissolved in 100 mL of ethanol anhydrous (99.5% purity, Dinâmica) and then under vigorous stirring, 22.5 mL of distilled water was added dropwise at room temperature for 12 h. After that, the suspension was cleaned by dialysis in 5 L of distilled water, often renewed, until removing all chloride ions, which was confirmed by tests with AgNO 3 solution (0.1 mol L −1 ).…”