Recent Advances in TiO2-based Photoanodes for Photoelectrochemical Water Splitting

Particle-Based Photoelectrodes for PEC Water Splitting: Concepts and Perspectives

This comprehensive review delves into the intricacies of the photoelectrochemical (PEC) water splitting process, specifically focusing on the design, fabrication, and optimization of particle-based photoelectrodes for efficient green hydrogen production. These photoelectrodes, composed of semiconductor materials, potentially harness light energy and generate charge carriers, driving water oxidation and reduction reactions. The versatility of particle-based photoelectrodes as a platform for investigating and enhancing various semiconductor candidates is explored, particularly the emerging complex oxides with compelling charge transfer properties. However, the challenges presented by many factors influencing the performance and stability of these photoelectrodes, including particle size, shape, composition, morphology, surface modification, and electrode configuration, are highlighted. The review introduces the fundamental principles of semiconductor photoelectrodes for PEC water splitting, presents an exhaustive overview of different synthesis methods for semiconductor powders and their assembly into photoelectrodes, and discusses recent advances and challenges in photoelectrode material development. It concludes by offering promising strategies for improving photoelectrode performance and stability, such as the adoption of novel architectures and heterojunctions.

Construction of Photothermo-Electro Coupling Field Based on Surface Modification of Hydrogenated TiO2 Nanotube Array Photoanode and Its Improved Photoelectrochemical Water Splitting

Solar water splitting has gained increasing attention in converting solar energy into green hydrogen energy. However, the construction of a photothermo-electro coupling field by harnessing light-induced heat and its enhancement on solar water splitting were seldom studied. Herein, we developed a full-spectrum responsive photoanode by depositing CdxZn1-xS onto the surface of hydrogenated TiO2 nanotube array (H-TNA), followed by modification with Ni2P. The resulting ternary photoanode exhibits a photocurrent density of 4.99 mA·cm-2 at 1.23 V vs. RHE with photoinduced heating, which is 11.9-fold higher than that of pristine TNA, with an optimal ABPE of 2.47%. The characterization results demonstrate that the ternary photoanode possesses superior full-spectrum absorption and efficient photogenerated carrier separation driven by the interface electric fields. Additionally, Ni2P reduces the hole injection barrier and increases surface active sites, accelerating the consumption of holes accumulating on the relatively unstable CdxZn1-xS to simultaneously improve the activity and stability of water splitting. Moreover, temperature-dependent measurements reveal that H-TNA and Ni2P significantly motivate the photothermal conversion to construct a photothermo-electro coupling field, optimizing photoelectric conversion and charge carrier-induced surface reactions. This work contributes to understanding the synergistic effect of the photothermo-electro coupling field on the photoelectrochemical water splitting.

Architecture design of TiO2 with Co-doped CdS quantum dots photoelectrode for water splitting

Photoelectrochemical hydrogen production is a critical key to solving the carbon-zero goal of countries due to renewable sources of solar light and combustion products of hydrogen-only water. Here, an architecture design for an n-type nano rosettes-rod TiO2 (RT) surface using CdS and Co-doped CdS quantum dots (QDs) is carried out utilizing the SILAR (simple ionic layer adsorption and reaction) method. Furthermore, the photocatalytic behaviour of Co-doped CdS QDs SILAR cycles deposition is investigated in various cycles, including 5, 8, 10, and 12. The FESEM, Raman XRD, Uv-Vis spectrometer, and vibration modes are used to evaluate the photoelectrode surface structure, crystal structure, and solar light absorption, respectively. FESEM images and XRD pattern revealed successive CdS QDS and Co-doped CdS QDs deposition on the RT boundary and rising SILAR cycles of Co-doped CdS QDs lead to further coverage of RT surface. UV-vis spectrometer indicated shifting solar light absorption to the visible region by applying more SILAR cycles of Co-doped CdS QDs deposition. The electrochemical parameters obtained from EIS showed total polarization resistance (Rp) of the RT electrode dramatically decreased with 10 SILAR cycle Co-doped CdS QDs deposition (5093 Ω cm2 and 617 Ω cm2). Linear sweep voltammetry (LSV) and chronoamperometric photocatalytic performance measurements indicated Co-doped CdS QDs on RT extremely enhanced photoresponse under solar irradiation and 10 SILAR cycle Co-doped CdS QDs improved photocurrent density about fourfold according to blank RT electrode.

Two-Dimensional Sb Modified TiO2 Nanorod Arrays as Photoanodes for Efficient Solar Water Splitting

As one of the widely studied semiconductor materials, titanium dioxide (TiO₂) exhibits high photoelectrochemical (PEC) water-splitting performance as well as high chemical and photo stability. However, limited by a wide band gap and fast electron-hole recombination rate, the low solar-to-hydrogen conversion efficiency remains a bottleneck for the practical application of TiO₂-based photoelectrodes. To improve the charge separation and water oxidation efficiency of TiO₂ photoanodes, antimonene, a two-dimensional (2D) material obtained by liquid-phase exfoliation, was assembled onto TiO₂ nanorod arrays (TNRAs) by a simple drop-coating assembly process. PEC measurements showed that the resulting 2D Sb/TiO₂ photoelectrode displayed an enhanced photocurrent density of about 1.32 mA cm^-2 in 1.0 M KOH at 0.3 V vs. Hg/HgO, which is ~1.65 times higher than that of the pristine TNRAs. Through UV-Vis absorption and electrochemical impedance spectroscopy measurements, it was possible to ascribe the enhanced PEC performances of the 2D Sb/TiO₂ photoanode to increased absorption intensity in the visible light region, and improved interfacial charge-transfer kinetics in the 2D Sb/TiO₂ heterojunction, which promotes electron-hole separation, transfer, and collection.