Electrophoretic fabrication of alcohol-stable CsPbBr₃nanocrystalline photoelectrodes for formaldehyde production

Beyond their established role in photovoltaics and optoelectronics, halide perovskites (HPs) are emerging as promising photoactive materials for solar-driven (photo)electrochemical (PEC) reactions, aimed at fuel and energy generation. However, their fast degradation in polar solvents severely affects their PEC redox performance, making protective coatings or the use of non-polar systems essential to preserve their structural integrity. Here, we report the fabrication of bulky quaternary ammonium-stabilized CsPbBr₃ perovskite nanocrystal (PNC) photoanodes via butanol (BuOH)- mediated electrophoretic deposition (ED), without any encapsulation, exhibiting high PEC performance in fully alcoholic environments. By carrying out the ED of PNCs in the presence of didodecyldimethylammonium bromide (DDAB) dissolved in BuOH, we modulate the PEC behavior of the films, obtaining an average photocurrent of 1.17 ± 0.19 mA cm⁻² with a maximum value up to 1.45 mA cm⁻² in methanol (MeOH) under visible light irradiation. We attribute this performance to a fine balance between DDAB-mediated surface defect passivation, limited alcohol permeation and efficient electron transport within the PNC active layer. These factors collectively result in a high oxidizing power, enabling the selective conversion of MeOH into formaldehyde, with a faradaic efficiency ∼60% after 30 min of continuous operation. This work offers a novel and facile approach to fabricate high-quality PNC photoelectrodes with enhanced PEC activity for solar-driven chemical reactions in polar solvents.