Holes and electrons in CdSe nanoplatelets

Treball final de Grau en Química. Codi: QU0943. Curs acadèmic 2015-201

Efficient Ligand Passivation Enables Ultrastable CsPbX3 Perovskite Nanocrystals in Fully Alcohol Environments

Halide perovskite nanocrystals (PNCs) have demonstrated their wide potential to fabricate efficient optoelectronic devices and to prepare promising photocatalysts for solar-driven photo(electro)chemical reactions. However, their use in most of the practical applications is limited due to the instability of PNCs in polar environments. Here, the preparation of non-encapsulated CsPbX3 nanocrystals dispersed in fully alcohol environments, with outstanding stability through surface defect passivation strategy is reported. By using didodecyldimethylammonium bromide (DDAB) during material post-treatment, highly luminescent CsPbBr3 PNCs with remarkable stability in methanol/butanol medium up to 7 months with near-unity photoluminescence quantum yield are achieved. This approach is extrapolated to stabilize iodine-based CsPbBr3-xIx and CsPbI3 PNCs, showing an improvement of their photoluminescence features and stability in these high polar alcohols up to 6 h. DDAB mediates the defect suppression through ligand exchange and avoids the full permeation of alcohol to be in contact with the PNCs. In this context, DDAB induces ionization of alcohol molecules to strengthen the surface passivation. The findings open the door to the development of long-term stable CsPbX3 PNCs with high optical performance to be used in polar environments.This work was supported by the European Innovation Council (EIC) via OHPERA project (grant agreement 101071010), the Spanish Ministry of Science and Innovation under projects STABLE (PID2019-107314RB-I00) and ECOCAT (PID2020-116093RB-C41), the Spanish Ministry of Science and Innovation under project She-LED (PID2021-122960OA-I00), and the Generalitat Valenciana via Prometeo Grant Q-Solutions (CIPROM/2021/078). C.A.M. acknowledges APOSTD grant (APOSTD/2021/251) for funding. The authors also thank the Ministry of Education, Youth and Sports of the Czech Republic for the financial support of XPS measurements using CEMNAT infrastructure (project LM 2018103). The authors are very grateful to the “Serveis Centrals d'Instrumentació Científica (SCIC)” of the Universitat Jaume I

Switchable All Inorganic Halide Perovskite Nanocrystalline Photoelectrodes for Solar-Driven Organic Transformations

All inorganic halide perovskite nanocrystals (NCs) are considered as fascinating materials for a wide range of optoelectronic applications encompassing photovoltaics, lasing, sensing, and photocatalysis due to their outstanding optoelectronic properties. Herein, it is demonstrated that the photoelectrochemical behavior of CsPbBr3 NC films can be tailored through engineering the selective contacts and accepting species in the electrolyte. This concept has been successfully applied to the photoelectrochemical oxidation of benzyl alcohol (BzOH) to benzyl aldehyde (BzCHO) and the reverse photoelectrochemical reduction of BzCHO to BzOH, demonstrating that CsPbBr3 NCs activate both reactions with photocurrents up to 40 μA cm 2 toward BzCHO production and 5 μA cm 2 for the reverse reaction at 0.15 V versus normal hydrogen electrode. The obtained results highlight the huge potential and versatility of halide perovskite NCs for photoelectrocatalytic applications, validating the implementation of these materials for a wide range of solar-driven complex organic transformations, and emphasizing the urgent need for stabilization strategies to move beyond the proof-of-concept stage to relevant technological developments

Highly Durable Nanoporous Cu2–xS Films for Efficient Hydrogen Evolution Electrocatalysis under Mild pH Conditions

Copper-based hydrogen evolution electrocatalysts are promising materials to scale-up hydrogen production due to their reported high current densities; however, electrode durability remains a challenge. Here, we report a facile, cost-effective, and scalable synthetic route to produce Cu2–xS electrocatalysts, exhibiting hydrogen evolution rates that increase for ∼1 month of operation. Our Cu2–xS electrodes reach a state-of-the-art performance of ∼400 mA cm–2 at −1 V vs RHE under mild conditions (pH 8.6), with almost 100% Faradaic efficiency for hydrogen evolution. The rise in current density was found to scale with the electrode electrochemically active surface area. The increased performance of our Cu2–xS electrodes correlates with a decrease in the Tafel slope, while analyses by X-ray photoemission spectroscopy, operando X-ray diffraction, and in situ spectroelectrochemistry cooperatively revealed the Cu-centered nature of the catalytically active species. These results allowed us to increase fundamental understanding of heterogeneous electrocatalyst transformation and consequent structure–activity relationship. This facile synthesis of highly durable and efficient Cu2–xS electrocatalysts enables the development of competitive electrodes for hydrogen evolution under mild pH conditions.Funding for open access charge: CRUE-Universitat Jaume IICN2 acknowledges funding from Generalitat de Catalunya 2021SGR00457. This study is part of the Advanced Materials programme and supported by MCIN with funding from European Union NextGenerationEU (PRTR-C17.I1), Generalitat de Catalunya, and the Basque Government (grant IT1591-22). The authors thank the support from the projects (RED2022-134508-T, PID2020-116093RB-C41, PID2020-116093RB-C43, and PID2020-116093RB-C44) funded by MCIN/AEI/10.13039/501100011033/ and the project TED2021-129999A-C33 financed by MCIN/AEI/10.13039/501100011033 and European Union NextGenerationEU/PRTR. C.A.M. acknowledges funding from UJI postdoc fellowship POSDOC/2019/20, the Generalitat Valenciana for the APOSTD/2021/251 fellowship, and to MinCiencias Colombia through the Fondo Nacional de Financiamiento para la Ciencia, la Tecnología y la Innovación “Francisco José de Caldas”, call 848-2019. ICN2 is supported by the Severo Ochoa program from Spanish MCIN/AEI (Grant No.: CEX2021-001214-S) and is funded by the CERCA Programme/Generalitat de Catalunya. M.C.S. has received funding from the post-doctoral fellowship Juan de la Cierva Incorporation from MICINN (JCI-2019) and the Severo Ochoa programme. S.B. acknowledges grant RYC-2017-21931 funded by MCIN/AEI/10.13039/501100011033 and by ESF Investing in Your Future, EUR2020-112066 funded by MCIN/AEI /10.13039/501100011033 and by European Union NextGenerationEU/PRTR, and UPV/EHU project EHUrOPE19/01. J.R. acknowledges the Czech Science Foundation and funding from PIF outgoing project number 22-18079O

The role of oxygen vacancies in water splitting photoanodes

Photoelectrochemical water splitting has become one of the most reliable solar-energy conversion technologies for clean hydrogen production. In the race of developing and understanding new semiconducting materials for this application, several studies have been focused on the role of oxygen vacancies, which are known to be defects with a high impact on the final optical and electrical properties of the photoelectrodes. These oxygen defective states can introduce either favorable or detrimental pathways to the overall PEC performance. The present topical review aims to summarize the role of oxygen vacancies in four of the most studied semiconducting thin film oxides (BiVO4, Fe2O3, TiO2 and WO3) as photoanodes for solar water splitting