Publication: Carbon dioxide reduction with methane over cerium oxide and indium oxide nanocomposite photocatalysts
| datacite.subject.fos | oecd::Engineering and technology::Chemical engineering | |
| dc.contributor.author | Tharani Kulandaivalu | |
| dc.date.accessioned | 2025-05-15T01:26:31Z | |
| dc.date.available | 2025-05-15T01:26:31Z | |
| dc.date.issued | 2023-01-01 | |
| dc.description.abstract | Photocatalytic carbon dioxide (CO2) reduction with methane (CH4) offers a great potential to convert two notorious greenhouse gases to value-added fuels using inexhaustible solar energy. The present study aimed to develop novel silver (Ag) and ceria (CeO2) modified indium oxide (In2O3) photocatalysts for photocatalytic CO2 reduction with CH4 to convert highly stable CO2 and CH4 into syngas. At first, a comparison study was conducted for CeO2/In2O3 composite photocatalysts that were synthesised using two different facile methods, namely wet-impregnation (WI) and hydrothermal co-precipitation (CP) methods and the as-synthesised composite were denoted as CeO2/In2O3-WI and CeO2/In2O3-CP, respectively.The morphological observation verified the formation of interfaces between CeO2 and In2O3 in both the CeO2/In2O3 samples. Both preparation methods resulted in the formation of Ce3+ entities as predominant species on the surface of CeO2/In2O3. The presence of higher content of Ce3+ reflected a strong interfacial contact between CeO2 and In2O3 indicating the formation of heterojunction. However, CeO2/In2O3-WI produced excess portion of Ce3+ species and oxygen vacancies that became recombination centers. The photocatalytic CO2 reduction with CH4 results revealed that the reaction over CeO2/In2O3-CP formed a total yield of 174 μmol/gcat CO and H2 and was 1.5 and 3.6 times higher than that of CeO2/In2O3-WI. However, the selectivity of CO over CeO2/In2O3-WI was higher than that of CeO2/In2O3-CP, with a selectivity of 94 and 85% respectively. When H2O was used as reductant to substitute CH4, the selectivity of H2 was gradually suppressed from 26 % to 9 and 4 % over 0.2 CeO2/In2O3-WI and 0.2 CeO2/In2O3-CP respectively. Based on the experiment findings, the superior photoactivity of CeO2/In2O3-CP was ascribed to its smaller and uniform particle size distribution, higher surface area, enhanced light absorption capacity and suppressed recombination of electron-hole pairs as compared to CeO2/In2O3-WI. Following that, a non-precious Ag metal was photodeposited over CeO2/In2O3-CP to construct Ag-CeO2/In2O3 ternary photocatalysts for photocatalytic CO2 reduction with CH4. At an optimum loading of 0.5 wt. %, the formation of CO and H2 was improved remarkably with a total yield of 253 μmol/gcat which is about ~0.5 times higher than that of binary CeO2/In2O3. A mechanism of reaction was developed based on Type II heterojunction for Ag-CeO2/In2O3 photocatalyst in which charges travel in the direction of In2O3→CeO2→Ag where Ag acts as an electron sink to effectively trap electrons from CeO2, reducing their recombination. Among the operating parameters studied, feed ratio was the most influential to drastically affect the product yield. The stability test showed prolonged stability and reusability of Ag-CeO2/In2O3 in five cycles of photoreaction. The Langmuir–Hinshelwood model revealed that yield rates of products were dependent on efficient adsorption of the reactants and desorption of products over the photocatalyst surface. In conclusion, this study proved the conversion of CO2 and CH4 to syngas using photon energy over the novel highly efficient Ag-CeO2/In2O3 photocatalysts. | |
| dc.identifier.uri | https://erepo.usm.my/handle/123456789/21633 | |
| dc.language.iso | en | |
| dc.title | Carbon dioxide reduction with methane over cerium oxide and indium oxide nanocomposite photocatalysts | |
| dc.type | Resource Types::text::thesis::doctoral thesis | |
| dspace.entity.type | Publication | |
| oairecerif.author.affiliation | Universiti Sains Malaysia |