Proceedings of Catalyst Design Strategies for Photo- and Electrochemical Fuel Synthesis (ECAT25)
Publication date: 19th December 2024
Oxygen evolution reaction (OER) is the limiting factor for energy conversion processes in aqueous media such as water splitting due to its high energy demand and sluggish, multistep kinetics. Typically, precious metal oxides like RuO2 or IrO2 are required to promote the reaction in an efficient way. For this reason, new alternatives with less critical, scarce and expensive materials are being explored. Photoanode materials like bismuth vanadates (BiVO4) appear as promosing candidates due to their ability to leverage sunlight and employ it for oxidation reactions. However, BiVO4 present some drawbacks that reduce its performance in photoanodes such as short hole diffusion length (~70 nm), low carriers mobility (~0.044 cm^2 V^-1 s^-1) and great surface recombination. Many strategies have been examined to tackle these inconveniences, some of which are nanostructuring, heterostructuring with other metal oxides, postsynthetic treatments, and deposition of cocatalysts.
In this work, we explore MOOH (M = Fe, Ni) as efficient cocatalysts over Zr:BiVO4 photoanodes towards OER. We characterize them structurally by x-ray diffraction and Raman spectroscopy, we examine the morphologies of the films by field emission scanning electronic microscopy and verify the cocatalysts present by elemental analysis via energy disperssive x-ray spectroscopy. We test the photoelectrochemical properties by linear sweep voltammetry under chopped illumination and electrochemical impedance spectroscopy and we test the stability under operational conditions by chronoamperometry. Our findings show that the deposition of cocatalysts effectively enhance the photoelectrochemical properties of the devices in terms of photocurrent, photovoltage, fill factor, stability and charge transfer kinetics. Next steps will be focused on unraveling the underlying mechanism of water oxidation by operando techniques.
This work received funding from the European Union NextGenerationEU 2021 research and innovation program under SolFuture research project (PLEC2021-007906). Financial support was received from AEI-MICINN/FEDER, UE through N-GREEN project (PID2022-141688OB-I00). Moreover, thanks PIPF-2023/ECO-31189 fellowship funded by regional government of Comunidad de Madrid.