Tongming Su

Recent advances in the photocatalytic reduction of carbon dioxide

Fossil fuels are currently the major energy source and are rapidly consumed to supply the increasing energy demands of mankind. CO2, a product of fossil fuel combustion, leads to climate change and will have a serious impact on our environment. There is an increasing need to mitigate CO2 emissions using carbon–neutral energy sources. Therefore, research activities are devoted to CO2 capture, storage and utilization. For instance, photocatalytic reduction of CO2 into hydrocarbon fuels is a promising avenue to recycle carbon dioxide. Here we review the present status of the emission and utilization of CO2. Then we review the photocatalytic conversion of CO2 by TiO2, modified TiO2 and non-titanium metal oxides. Finally, the challenges and prospects for further development of CO2 photocatalytic reduction are presented.

Soft template inducted hydrothermal BiYO3 catalysts for enhanced formic acid formation from the photocatalytic reduction of carbon dioxide

Bismuth yttrium oxide (BiYO3) photocatalysts were hydrothermally prepared using sodium dodecyl benzene sulfonate (SDBS), disodium ethylenediamine tetraacetate (EDTA), and citric acid (CA) as soft templates. The effects of templates on the formed BiYO3 nanostructures were revealed. The BiYO3 nanostructures prepared without the existing template and with the existence of SDBS, EDTA, and CA as templates had flaked structures, sliced, rectangular lath structures with fine particles, and scaly uniform particles, respectively. The photocatalytic reduction of CO2 under visible-light irradiation with these synthesized BiYO3 nanostructures was studied and compared. Due to the larger specific surface area, higher adsorbed edge, and lower band gap, BiYO3 prepared using EDTA as a template produced fewer hydroxyl free radicals (·OH) to give a higher yield of formic acid (HCOOH) in the process of the photocatalytic reduction of CO2. The HCOOH yield from the photocatalytic reduction of CO2 by the EDTA synthesized BiYO3 was 1.68 μmol L−1, which was 1.9 times higher than that produced from BiYO3 prepared without a template, and 2.6 times higher than that of BiYO3 prepared by a solid-state reaction.

A zinc sulfide-supported iron tetrakis (4-carboxyl phenyl) porphyrin catalyst for aerobic oxidation of cyclohexane

Zinc sulfide-supported iron tetrakis (4-carboxyl phenyl) porphyrin (Fe TCPP/ZnS) was prepared and used for aerobic cyclohexane oxidation. X-ray diffraction, ultraviolet-visible spectroscopy and Fourier-transform infrared spectroscopy were carried out. The effects of oxygen pressure, reaction temperature, amount of iron tetrakis (4-carboxyl phenyl) porphyrin (Fe TCPP) and reaction time on the Fe TCPP/ZnS-catalyzed cyclohexane oxidation process were investigated. Fe TCPP/ZnS exhibited excellent activity for aerobic cyclohexane oxidation. Under optimal reaction conditions, the turnover number, cyclohexane conversion, cyclohexanone and cyclohexanol yields were 8.6 × 105, 64.9% and 24.4%, respectively. The stability of Fe TCPP was improved after immobilization on zinc sulfide (ZnS), and the catalyst maintained nearly original levels of activity after several reaction cycles.

One-Step Synthesis of Nb2O5/C/Nb2C (MXene) Composites and Their Use as Photocatalysts for Hydrogen Evolution

Hydrogen production through facile photocatalytic water splitting is regarded as a promising strategy to solve global energy problems. Transition-metal carbides (MXenes) have recently drawn attention as potential co-catalyst candidates for photocatalysts. Here, we report niobium pentoxide/carbon/niobium carbide (MXene) hybrid materials (Nb2 O5 /C/Nb2 C) as photocatalysts for hydrogen evolution from water splitting. The Nb2 O5 /C/Nb2 C composites were synthesized by one-step CO2 oxidation of Nb2 CTx . Nb2 O5 grew homogeneously on Nb2 C after mild oxidation, during which some amorphous carbon was also formed. With an optimized oxidation time of 1.0 h, Nb2 O5 /C/Nb2 C showed the highest hydrogen generation rate (7.81 μmol h-1  gcat-1 ), a value that was four times higher than that of pure Nb2 O5 . The enhanced performance of Nb2 O5 /C/Nb2 C was attributed to intimate contact between Nb2 O5 and conductive Nb2 C and the separation of photogenerated charge carriers at the Nb2 O5 /Nb2 C interface; the results presented herein show that transition-metal carbide are promising co-catalysts for photocatalytic hydrogen production.

Intrinsic Kinetics of Dimethyl Ether Synthesis from Plasma Activation of CO2 Hydrogenation over Cu-Fe-Ce/HZSM-5.

CO2 is activated in a plasma reactor followed by hydrogenation over a Cu-Fe-Ce/HZSM-5 catalyst, and the intrinsic kinetics of the plasma catalytic process are studied. Compared with CO2 hydrogenation using Cu-Fe-Ce/HZSM-5 alone, the CO2 conversion and the dimethyl ether selectivity for the plasma catalytic process are increased by 16.3 %, and 10.1 %, respectively, indicating that the CO2 was activated by the plasma to promote hydrogenation. A study of the intrinsic kinetics shows that the activation energies of methanol formation, the reverse water-gas shift reaction, and methanol dehydration to dimethyl ether are 149.34, 75.47, and 73.18 kJ mol-1 , respectively, which are lower than if Cu-Fe-Ce/HZSM-5 is used without plasma, indicating that the activation of CO2 in the plasma reduces the activation energy of the hydrogenation reaction and improves the yield of dimethyl ether.

Photocatalytic Reduction of Carbon Dioxide

Reduction is an effective way to convert carbon dioxide (CO2), a greenhouse gas, into compounds that can be further used for materials and energy. Here we discuss the emission and utilization of CO2. Then we review the photocatalytic conversion of CO2 with emphasis on the use of TiO2, modified TiO2 and non-titanium metal oxides. Finally, the challenges and prospects for further development of CO2 photocatalytic reduction are presented.