Wykład zatytułowany Rational design of photoelectrodes for photoelectrochemical water splitting: from structural to electronic properties wygłosi dr Taymaz Tabari z Wydziału Chemii Uniwersytetu Jagiellońskiego.
Water splitting is an uphill reaction, which needs 237 kJ to produce one mole of hydrogen. To provide it, solar energy can be used to oxidize/reduce water. Despite the numerous attempts to design efficient photoelectrodes in solar water splitting, the reported efficiency is far from reaching the expected theoretical values. This stems from the intrinsic slow charge transportation, and inefficient charge separation, along with poor oxidation kinetics of the photocatalysts such as TiO2, Fe2O3, etc. Norskov et al. have shown that these photocatalytic systems are unable to efficiently produce oxygen, favoring the production of H2O2. This phenomenon points to the importance of employing active oxygen evolution reaction (OER) electrocatalysts to increase the efficiency of water splitting in a PEC system. On the other hand, an efficient charge separation at the bulk is a necessity for a photocatalytic system. In this context, 1D materials due to their directional charge transfer showed promising efficacy in charge separation. Herein, we have used a fundamental approach to design active photoelectrodes for solar water splitting constructed in a heterojunction architecture. The materials were synthesized employing hydrothermal, and sol-gel methods, while to build the heterojunction architecture a spin-coater was used. The photoelectrodes were studied using XRD, XPS, SEM, TEM, UPS, Kelvin probe, and electrochemical methods. The photoelectrochemical (PEC) activity is studied in a gas-tight reactor with an irradiation widow of 1 cm2. In this collective study, we have shown that the most efficient 1D structure photoelectrodes are constructed from long rods with small diameters, which dramatically decreases charge recombination and increases charge separation. Such rods amounted to 0.24% “applied bias photon to current efficiency”, which was among the highest activities reported for pristine and heterojunction TiO2. However, the activity of the photoelectrodes correlates with the OER activity of the catalysts employed to oxidize water. In a series of La1–xSrxFeO3 (x = 0, 0.2, 0.4), we have shown that the catalytic activity and the overall PEC activity of the photoelectrodes are correlates with the length of Fe–O bond in these perovskites. The overall activity of the photoelectrodes in solar water splitting was a function of the band bending degree and hole consumption at the interface with electrolyte. High solar to hydrogen efficiency can be obtained when both factors are designed to perform efficiently. However, the hole transfer at bulk and specifically at the interface of two semiconductors in a heterojunction design is hindered by the increased oxygen vacancies and decreased conductivity. Therefore, to improve the charge transfer at the bulk and diminish the back charge transfer, reduced graphene oxide is employed as a 2D mediator to direct the holes to the surface of the photoanode, while at the same time preventing back electron transfer. This architecture, constructed from 1D@2D@0D architecture, demonstrated a performance among the highest activities reported for Fe2O3-based photoelectrodes, which are related to its optimized electronic and structural properties.
W tym semestrze seminarium dotychczas organizowane przez Akademickie Centrum Materiałów i Nanotechnologii będzie połączone z Krakow Condensed Matter Seminar (zwane wcześniej Środowiskowym Seminarium Fizyki Ciała Stałego). Począwszy od 1 marca 2023 r. spotkania odbywać się będą w środy o godz. 9.00 i prowadzone będą hybrydowo: stacjonarnie (w siedzibie ACMiN przy ul. Kawiory 30, bud. D-16, sala audytoryjna 1.02A na II piętrze) oraz z transmisją online na platformie MS Teams.