Photoelectrochemical biomass valorisation using an integrated PV- PEC approach Irene Carrai a , Raffaello Mazzaro a,b, *, Alberto Piccioni a,b , Marco Salvi a , Luca Pasquini a,b a Department of Physics and Astronomy, University of Bologna, Viale Berti Pichat 6/2, 40127, Bologna, Italy, b Institute for Microelectronics and Microsystems, National Research Council, via Gobetti 101, 40129, Bologna, Italy The sluggish kinetics of the oxygen evolution reaction (OER) is a bottleneck in solar water splitting, limiting the Solar-to-Hydrogen (STH) conversion efficiency and hindering its competitiveness with fossil-based technologies. To overcome this challenge, researchers are increasingly exploring alternative oxidation reactions that require less energy and utilize cost-effective starting materials. In this study, we investigate the photoelectrochemical oxidation of biomass-derived compounds into value-added chemicals by using Metal Oxides Semiconductors (MOS). Titanium-doped hematite (Ti:Fe 2 O 3 ) photoanodes were employed to oxidize 5-hydroxymethylfurfural (HMF) into 2,5-furandicarboxylic acid (FDCA), a key precursor for PEF plastic. Initially, a borate buffer solution (pH 9) with (2,2,6,6-Tetramethylpiperidin-1-yl)oxyl (TEMPO) as a mediator was used. To mitigate competition with the oxygen evolution reaction (OER), the photoanode surface was modified with cobalt-based cocatalysts, and cobalt phosphate (CoPi) exhibited the highest selectivity for TEMPO-mediated oxidation, achieving an FDCA yield of 86%. Electrochemical impedance spectroscopy (EIS) and intensity-modulated photocurrent spectroscopy (IMPS) attributed this enhancement to reduced charge carrier recombination in the presence of the CoPi cocatalyst. To eliminate the need for TEMPO, nickel-based electrocatalysts (Ni(OH) 2 and NiMo) were deposited on Ti:Fe 2 O 3 and tested under alkaline conditions (pH 13), resulting in partial HMF conversion. Operando X-ray absorption spectroscopy (XAS) demonstrated selective hole scavenging by HMF on Ni-based electrocatalysts, enabling the reaction to proceed at the expense of OER without requiring an electron mediator. Additionally, bismuth vanadate (BiVO 4 ) photoanodes were investigated for glycerol oxidation to dihydroxyacetone (DHA) under acidic conditions. Photoanode stability was assessed through long-term chronopotentiometry, while structural analysis was conducted using X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM). To develop a stand-alone device, these biomass valorisation reactions were then integrated with a photovoltaic (PV) cell, eliminating the need for an external bias. A dichroic mirror was used to optimize light utilization, by splitting the excitation light from the solar simulator. The transmitted blue light—aligned with the semiconductor’s bandgap—was precisely directed onto the photoanode, while the remaining lower-energy wavelengths were reflected and efficiently absorbed by the PV cell. By optimizing this setup, we sought to improve the performance of the photoanodic material for the targeted oxidation reaction, while efficiently utilizing the electricity generated by the solar cell to drive parallel processes, such as hydrogen evolution or additional electrochemical conversions. When designing a photoelectrochemical device, advanced operando kinetic analyses offer crucial insights into the underlying reaction mechanisms, while long-term photostability assessments ensure the efficient utilization of these materials. By integrating these optimizations with the PV-PEC approach, we can not only enhance overall energy conversion efficiency but also expand the potential applications of sustainable, solar-driven photoelectrochemical systems. References 1. Cha HG, Choi KS. Nat Chem . 2015 ; 7(4):328-333. 2. Bender MT, Choi K. ChemSusChem 2022 , 15, e202200675. 3. Carrai I, Mazzaro R, Bassan E, et al. Solar RRL 2023 ;2300205:1-13. 4. Carrai I, Mazzaro R, Bellatraccia C, et al.ChemSusChem, 2025 , e202402604.
P126
© The Author(s), 2025
Made with FlippingBook Learn more on our blog