Fulfilling the growing demand for energy via renewable resources while minimizing CO2 emissions has become one of the world’s great challenges. One such system capable of renewable solar energy conversion for storage is photoelectrochemical water splitting into hydrogen and oxygen. Previously, a photoanode composed of nanostructured SnO2 coated with a perylene diimide dye derivative, N,N′-bis(phosphonomethyl)-3,4,9,10-perylenediimide (PMPDI), plus photoelectrochemically deposited cobalt oxide (CoOx) catalyst, represented as FTO/SnO2/PMPDI/CoOx, was shown to photoelectrochemically oxidize water with 31 ± 7% Faradaic efficiency. However, the addition of the known water-oxidation catalyst (WOC) CoOx to this system resulted in an undesired reduction of the total photocurrent due to an increase in charge-carrier recombination. Hence, we strove to understand this “anti-catalytic” behavior by examining the role of C-impurities in the nano-SnO2. We show deposition of a more defect free, phase pure SnO2 layer applied by atomic layer deposition (ALD) instead of the nano-SnO2 can improve the photoactivity and catalytic activity of the system. Crucially, the addition of the CoOx catalyst improves photocurrents and decreases recombination in systems without nano-SnO2, improving the Faradaic efficiency to 45 ± 5.5%. Using a series of controls in which the C-based impurity was altered, we observed changes in charge-carrier recombination, offering us insight into the recombination kinetics involved with C-based impurities. Additionally, we show that we can semi-quantitatively compare systems with differing electrochemically active surface areas and amounts of dye. These results indicate that thoughtful characterization and synthesis of dye sensitized solar cells is critical to understanding and improving the charge-transfer kinetics in such complex systems.

Understanding the role of carbon-based impurity and resultant defects in DS-PECs: Atomic layer deposition of tin oxide en route to improved photoelectrochemical water oxidation catalysis

ACS Spring 2022

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.