(558h) Multiple Applications of 2D Titanium Carbide (MXene) in Photoelectrochemical Water Splitting: Cocatalysts, Surface Modifications and Matrix for Chemical Transformation
AIChE Annual Meeting
2019
2019 AIChE Annual Meeting
Poster Sessions
General Poster Session II
Wednesday, November 13, 2019 - 3:30pm to 5:00pm
Transition metal carbides and carbonitrides (MXenes), a newly explored family of 2D materials has expanded rapidly since discovered in 2011. Due to their unique in-plane anisotropic structures, excellent metallic conductivity and hydrophilicity, MXenes have shown attractive applications in energy storage and biology fields. As the most studied MXenes, 2D titanium carbides (Ti3C2Tx MXene) can be readily obtained by etching the Al layer of MAX phase Ti3AlC2 with HF. The Tx was the surface terminated functional groups such as âO, âF, or âOH. Although the Ti3C2Tx MXene has been used in photocatalysis, the potential applications of the Ti3C2Tx MXene in photoelectrochemical (PEC) water splitting have not been rigorously investigated. The present study focuses on the multiple applications of 2D Ti3C2Tx MXene in PEC water splitting, which has been carried out from the following three aspects:
- As co-catalysts, the 2D Ti3C2Tx MXene can facilitate the charge transfer of the photogenerated carriers and reduce the charge recombination of the BiVO4 photoanode. A composite photoanode of Ti3C2Tx/BiVO4 was fabricated by spin coating thin Ti3C2Tx MXene flakes onto the surface of a BiVO4 film grown on the FTO substrate. The coating of thin Ti3C2Tx flakes onto the BiVO4 film would boost the photocurrent density from 2.95 to 3.45 mA cmâ2, exhibiting a photoconversion efficiency of 0.78% and a surface charge separation efficiency of 73%.
- For surface modifications, the oxygen vacancies enriched Ti3C2Tx flakes can be obtained by reducing Ti3C2Tx with H2/Ar gas (denoted as H:Ti3C2Tx). The H:Ti3C2Tx/Cu2O, Ti3C2Tx/Cu2O as well as Au/Cu2O composite photocathodes are fabricated through a facile dip-coating method. The H:Ti3C2Tx/Cu2O and Ti3C2Tx/Cu2O yield a photocurrent density of -5.41 and -4.45 mA cm-2 respectively, which is higher than the bare Cu2O and Au/Cu2O (-4.31 mA cm-2). The results suggest that the Ti3C2Tx is more effective than noble metal Au for improving the PEC performance of Cu2O photocathode. The superior performance of H:Ti3C2Tx/Cu2O is attributed to enriched oxygen vacancies in the H:Ti3C2Tx which can enhance the conductivity, light-harvesting efficiency and charge-transfer ability of fabricated photocathode.
- As matrix for chemical transformation, the {001} facets exposed TiO2 flakes were derived from the delaminated Ti3C2Tx MXene (D-Ti3C2Tx) without adding extra HF or F ions by a facile hydrothermal synthesis because the surface of D-Ti3C2Tx was natively terminated by -F functional groups. The Sn-doped α-Fe2O3 nanorods were embedded with the {001} facets exposed TiO2 flakes (denoted as E-Sn-Fe2O3/TiO2). The Sn-doped hematite/surface-covered TiO2 (denoted as S-Sn-Fe2O3/TiO2) and Sn-doped hematite (denoted as Sn-Fe2O3) were also fabricated for comparison. Under simulated sunlight, the E-Sn-Fe2O3/TiO2 yielded a photocurrent density of 0.85 mA cm-2 at 1.23 V (vs. RHE) compared with 0.72 mA cm-2 and 0.42 mA cm-2 for S-Sn-Fe2O3/TiO2 and Sn-Fe2O3, respectively. The E-Sn-Fe2O3/TiO2 achieved an IPCE value of 18.6% at 380 nm (15.8% for S-Sn-Fe2O3/TiO2 and 10.4% for Sn-Fe2O3) and exhibited enhanced IPCE values at all measured wavelengths compared with the other two photoanodes. The unique architecture of embedded TiO2 can improve the interfacial contact between the α-Fe2O3 and TiO2 as well as the light harvesting of the α-Fe2O3 compared with the surface-covered TiO2, contributing to the better charge transport ability and enhanced PEC performance.