Role of active species formed by electrolysis on electrochemical therapy

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Bifunctional atomically dispersed ruthenium electrocatalysts for efficient bipolar membrane water electrolysis

Atomically dispersed catalysts (ADCs) have recently drawn considerable interest for use in water electrolysis to produce hydrogen, because they allow for maximal utilization of metal species, particularly the expensive and scarce platinum group metals. Herein, we report the electrocatalytic performance of atomically dispersed ruthenium catalysts (Ru ADCs) with ultralow Ru loading (0.2 wt%). The as-obtained Ru ADCs (Ru (0.2)-NC) are active for both hydrogen evolution reaction (HER) and oxygen evolution reaction (OER), which only require a low overpotential (η) of 47.1 and 72.8 mV to deliver 10 mA cm for HER in 0.5 M HSO and 1.0 M KOH, respectively, and of 300 mV for OER in 1.0 M KOH, showing favorable bifunctionality. Density functional theory (DFT) calculations reveal that the Ru-N bonding plays an important role in lowering the energy barrier of the reactions, boosting the HER and OER activities. Furthermore, the bipolar membrane (BPM) water electrolysis using the bifunctional Ru (0.2)-NC as both HER and OER catalysts can afford 10 mA cm under a low cell voltage of only 0.89 V, and does not show any performance decay upon 100 h continuous operation, showing great potential for energy-saving hydrogen production.L. L. acknowledges the financial support from the National Innovation Agency of Portugal through the Mobilizador Programme (Baterias 2030, Grant No. POCI-01-0247-FEDER-046109). B. L. acknowledges the Natural Science Foundation of LiaoNing Province, China (Grant No. 20180510014) for funding. Z. P. Y. is grateful for the scholarship offered by the China Scholarship Council (Grant No. 201806150015). This work was also in part financially supported by: LA/P/0045/2020 (ALiCE), UIDB/50020/2020 and UIDP/50020/2020 (LSRE-LCM) funded by national funds through FCT/MCTES (PIDDAC); project 2DMAT4FUEL (POCI-01-0145-FEDER-029600 - COMPETE2020 – FCT/MCTES - PIDDAC, Portugal). In addition, this work was carried out in part through the use of the INL Advanced Electron Microscopy, Imaging and Spectroscopy (AEMIS) Facility

Conformal and continuous deposition of bifunctional cobalt phosphide layers on p-silicon nanowire arrays for improved solar hydrogen evolution

Vertically aligned p-silicon nanowire (SiNW) arrays have been extensively investigated in recent years as promising photocathodes for solar-driven hydrogen evolution. However, the fabrication of SiNW photocathodes with both high photoelectrocatalytic activity and long-term operational stability using a simple and affordable approach is a challenging task. Herein, we report conformal and continuous deposition of a di-cobalt phosphide (Co2P) layer on lithography-patterned highly ordered SiNW arrays via a cost-effective drop-casting method followed by a low-temperature phosphorization treatment. The as-deposited Co2P layer consists of crystalline nanoparticles and has an intimate contact with SiNWs, forming a well-defined SiNW@Co2P core/shell nanostructure. The conformal and continuous Co2P layer functions as a highly efficient catalyst capable of substantially improving the photoelectrocatalytic activity for the hydrogen evolution reaction (HER) and effectively passivates the SiNWs to protect them from photo-oxidation, thus prolonging the lifetime of the electrode. As a consequence, the SiNW@Co2P photocathode with an optimized Co2P layer thickness exhibits a high photocurrent density of -21.9 mA.cm(-2) at 0 V versus reversible hydrogen electrode and excellent operational stability up to 20 h for solar-driven hydrogen evolution, outperforming many nanostructured silicon photocathodes reported in the literature. The combination of passivation and catalytic functions in a single continuous layer represents a promising strategy for designing high-performance semiconductor photoelectrodes for use in solar-driven water splitting, which may simplify fabrication procedures and potentially reduce production costsThis work was funded by ERDF funds through the Portuguese Operational Programme for Competitiveness and Internationalization COMPETE 2020, and national funds through FCT – The Portuguese Foundation for Science and Technology, under the project “PTDC/CTM-ENE/2349/2014” (Grant Agreement No. 016660). The work is also partially funded by the Portugal-China Bilateral Collaborative Programme (FCT/21102/28/12/2016/S). L. F. Liu acknowledges the financial support of the FCT Investigator Grant (IF/01595/2014) and Exploratory Grant (IF/01595/2014/CP1247/CT0001). L. Qiao acknowledges the financial support of the Ministry of Science and Technology of China (Grant Agreement No. 2016YFE0132400).info:eu-repo/semantics/publishedVersio

Identificação e quantificação dos produtos de eletrólises efectuadas em condições fisiológicas e estudo da sua atividade toxicológica utilizando leveduras como modelos celulares

Dissertação de mestrado em Técnicas de Caracterização e Análise QuímicaO tratamento eletroquímico (EChT) é uma modalidade alternativa para o tratamento de tumores com base na aplicação de uma corrente elétrica contínua no tecido tumoral, por meio de dois ou mais elétrodos colocados na zona do tumor ou nas áreas circundantes. Há relato de resultados promissores em ensaios clínicos realizados na China que mostram a regressão dos tumores, e em alguns casos a própria remissão total. Apesar destes resultados, tem havido muita relutância no mundo ocidental em aceitar este tratamento. A falta de evidências de natureza científica acerca do funcionamento destes tratamentos é uma das causas que pode justificar a falta de interesse pela medicina ocidental. Como resultado direto das eletrólises galvanostáticas que resultam da passagem de corrente elétrica nos tecidos, há referência à evolução de O2 no ânodo e de H2 no cátodo, provenientes da eletrólise da água. A maioria dos estudos in vitro reporta os efeitos relacionados com a acidificação na região do ânodo e da alcalinização na região do cátodo. Apesar de na presença de Cl- ser referida a evolução de Cl2 no ânodo, a sua deteção é normalmente realizada de uma forma qualitativa através do cheiro. A dissolução do Cl2 dá origem à formação do HOCl, que é por sua vez um potente agente oxidante com capacidade para reagir com diferentes componentes celulares. Este trabalho visa contribuir para o esclarecimento do papel do HOCl na eficiência do EChT. De modo a quantificar o HOCl produzido durante as eletrólises foi otimizado um método espectrofotométrico, baseado na reação com a curcumina. Este método permitiu a quantificação de quantidades muito reduzidas de HOCl em meio fisiológico (PBS) tendo sido utilizado posteriormente para quantificar esta espécie em diferentes condições experimentais relevantes na aplicação do EChT. Os ensaios realizados mostraram que a produção de HOCl depende fortemente das condições experimentais da eletrólise. Dos efeitos estudados, o pH do meio mostrou ser o mais importante na medida em que pode limitar a produção de HOCl mesmo em condições em que a dose aplicada é elevada (tempo longos e intensidade de corrente altas). A acidificação junto ao ânodo, que tende a aumentar com a dose do tratamento, reduz a extensão de formação do HOCl, tornando o processo menos eficiente. Quando existe comunicação entre os produtos formados no ânodo e no cátodo ocorre um efeito de alcalinização do meio. Este aumento de pH demonstrou ser efetivo na solubilização do Cl2 produzido no ânodo contribuindo para a formação de quantidades superiores de HOCl tanto por aumento da intensidade de corrente como do tempo de eletrólise. O efeito em células vivas do HOCl produzido nas eletrólises foi testado utilizando culturas da levedura S. Cerevisiae como modelo. Observou-se que baixas concentrações de HOCl afetam drasticamente a viabilidade celular. Esta espécie demonstrou ter efeitos citotóxicos provocando a oxidação intracelular.The electrochemical treatment (EChT) is an alternative approach for the treatment of tumours by applying a continuous electric current to the tumour by means of two or more electrodes placed in the tumour area or at its surroundings. There are reports on positive results in clinical trials conducted in China, showing the regression, and in some cases the complete remission of tumours. Despite these results, the Western world is reluctant to accept this treatment. The lack of scientific evidence on the mechanism of action of this treatment is one of the causes that may justify lack of interest for this treatment by Western medicine. As result of electric current, galvanostatic electrolysis of the extracellular medium occurs, taking place the O2 evolution at the anode and the H2 evolution at the cathode. The majority of the in vitro studies report the effect of acidification in the anode region and of alkalinization at the cathode region. Although in the presence of Cl-, Cl2 evolution is known to take place at the anode its production is reported following its odour detection. This work aims to contribute to the clarification of the role of HOCl in EChT efficiency. The dissolution of Cl2 gives rise to the formation of HOCl, which in turn is a potent oxidizing agent capable of reacting with different cellular material. In order to quantify the HOCl produced during electrolysis a spectrophometric method based on reaction with curcumin has been optimized. This method allowed the quantitation of small amounts of HOCl at the physiological medium (PBS) and was used to quantify this species formed in different experimental conditions that are relevant for EChT. Results show that the amount of HOCl produced depends strongly on the experimental conditions of the electrolysis. The pH demonstrated to be the most important variable that can limit the production of HOCl, even for a high dose (long time and high current intensity). The medium acidification that increases during the treatment reduces the extent of HOCl formation and makes the process less effective. When the electrolysis is carried out in conditions that enable the mixture between the products formed at the anode and at the cathode, the medium alkalinizing is noticed. The pH increase, which takes place with increasing current intensity and electrolysis time, is effective for solubilisation of the Cl2 produced at the anode and contributes to formation of higher amounts of HOCl. The effect in living cells of the HOCl produced by electrolysis was evaluated using culture of the yeast S. cerevisiae as model. It was observed that low concentrations of HOCl dramatically affect cell viability. This species was shown to have cytotoxic effects by causing intracellular oxidation

Electrocatalytic properties and applications of transition metal catalysts

Programa doutoral em Chemistry (ramo do conhecimento em Physical and Analytical Chemistry)O rápido crescimento populacional e a industrialização têm contribuído para a poluição ambiental devido ao uso de combustíveis fósseis para produção de energia e na libertação de contaminantes nas águas, o que representa uma ameaça aos ecossistemas, causando efeitos tóxicos em organismos vivos. O hidrogénio verde produzido a partir da eletrólise eletroquímica da água, usando fontes de energia renovável, tem surgido como uma solução mais sustentável para o fornecimento global de energia, tendo o potencial de promover a obtenção dos objetivos da neutralidade de carbono, por descarbonização em áreas como o transporte e as indústrias. Além disso, os sensores eletroquímicos têm sido reconhecidos como ferramentas cruciais para monitorizar informações químicas abrangentes, em particular na deteção de analitos perigosos e contaminantes residuais nas águas, como compostos fenólicos. De forma a obter tecnologias de alto desempenho, estas aplicações eletroquímicas requerem eletrocatalisadores mais eficientes e económicos. Esta tese foca por isso no desenvolvimento de materiais avançados com excelente atividade catalítica, com ênfase em fosforetos de metais de transição (FMTs). Vários materiais FMTs com diferentes morfologias, como nanofios e nanopartículas, foram sintetizados com sucesso e extensivamente caracterizados usando técnicas como microscopia eletrónica de varrimento (MEV), microscopia eletrónica de transmissão (MET), difração de raios X (DRX) e espectroscopia de fotoeletrões por raios X. Posteriormente, os materiais CoP-CoTe2 , Co-Ni-P/NF e CoNiP-Ir@CP foram investigados como materiais de elétrodo para a eletrólise da água. Os resultados demonstraram que tanto o CoP-CoTe2 como o Co-Ni-P/NF exibem um desempenho superior na eletrólise de água por membrana bipolar usando uma configuração de “polarização inversa” em comparação com a eletrólise de água por membrana de troca aniónica. Além disso, a configuração de “polarização direta” levou a um potencial menor através da redução da energia elétrica por meio da neutralização eletroquímica. O material CoNiP-Ir@CP, com reduzido teor de metal precioso, mostrou ser eficaz na eletrólise da água por membrana de troca de protões com excelente estabilidade. Além disso, CoNiP@rGO e xerogéis de carbono (CXs) foram investigados na deteção de compostos fenólicos. A interação sinérgica entre CoNiP e rGO facilitou a modulação da estrutura eletrónica, levando a um melhor desempenho catalítico do CoNiP@rGO, que resultou numa alta sensibilidade e baixo limite de deteção de Bisfenol A por parte do CoNiP@rGO. Além disso, os CXs mostraram propriedades texturais e químicas favoráveis para a deteção de hidroquinona, superando o rGO, tornando-os num excelente material de suporte para incorporar FMTs.Rapid population growth and industrialization have contributed to environmental pollution trough either the use of fossil fuels for energy production and the release of contaminates into water bodies, posing threats to ecosystems and causing toxic effects in living organisms, including humans. Green hydrogen produced by electrochemical water electrolysis using renewable energy sources has emerged as an environmentally sustainable solution to global energy supply. It has the potential to decarbonize transportation and hard-to-abate industries, thereby contributing to the achievement of carbon neutrality. Additionally, electrochemical sensors have been recognized as crucial tools for monitoring comprehensive chemical information, particularly for detecting hazardous analytes and trace contaminants in water, such as phenolic compounds. Both of these electrochemical applications require high efficient and cost-effective electrocatalysts to enable high-performance technologies. Therefore, this thesis focuses on the development of advanced materials with excellent catalytic activity as alternative electrocatalysts to conventional ones, with a specific emphasis on transition metal phosphides (TMPs). Various TMP materials with different morphologies, such as nanowires and nanoparticles, were successfully synthesized and extensively characterized using techniques such as scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS). Subsequently, the home-made CoP-CoTe2 , Co-Ni-P/NF and CoNiP Ir@CP materials were investigated as electrode materials for electrochemical water splitting. The results demonstrated that both CoP-CoTe2 and Co-Ni-P/NF exhibit superior performance in bipolar membrane water electrolysis (BPMWE) compared to anion exchange membrane water electrolysis using a “reverse bias” configuration. Moreover, the “forward bias” configuration enabled significantly lower external bias due to reduced required electrical energy through electrochemical neutralization. The CoNiP-Ir@CP material, with reduced precious group metal (PGM) content exhibited significant potential for proton exchange membrane (PEM) electrolysis and excellent stability. Furthermore, CoNiP@rGO and carbon xerogles (CXs) were investigated for the detection of phenolic compounds. The synergetic interaction between CoNiP and rGO facilitated the modulation of the electronic structure, leading to enhanced catalytic performance of CoNiP@rGO. Consequently, CoNiP@rGO on a glassy carbon electrode showed a low limit of detection and high sensitivity for the detection of Bisphenol A. Moreover, CXs showed favorable textural and chemical properties for hydroquinone sensing, surpassing those of rGO, making them an excellent support material for incorporating TMPs.I would also like to acknowledge the financial support of Fundação para a Ciência e Tecnologia (FCT) for turning this project possible with the financial support given, grant no. SFRH/BD/137546/2018 and COVID/BD/153233/2023, co-financed by the Fundo Social Europeu (FSE) through the Programa Operacional Regional Norte (Norte 2020)

Towards an improved electrocatalytic material for detection of polyphenols based on transition metal phosphides anchored on reduced graphene oxide

The design of advanced materials with catalytic activity for detection of a target molecule is key to construct a sensitive electrochemical sensor. Transition metal phosphides (TMPs) have recently attracted substantial interest and are widely investigated as electrode material in the field of energy conversion/storage. TMPs have also been exploited for electrochemical sensing showing promising results for molecular detection. In this work, we report the preparation of a composite consisting of bimetallic cobalt−nickel phosphide (CoNiP) nanoparticles supported on reduced graphene oxide (rGO) and study the impact of phosphorization and presence of rGO on the electrochemical response using hydroquinone (HQ) as a model phenolic compound. The results show that the catalytic performance of CoNiP@rGO is a consequence of the synergetic interaction between different atoms of CoNiP and rGO, where P increases the proton concentration at the electrode interface favoring a catalytic mechanism where metal centers are oxidized. In the presence of rGO this effect is suppressed due to the formation of high valence states of CoNiP. The remarkable electrocatalytic performance may originate from the modulation of the electronic structure together with the large electroactive surface area and low electron-transfer resistance, enabling CoNiP@rGO to be a promising candidate for electrochemical sensor construction.Thanks are due to Fundação para a Ciência e Tecnologia (FCT) and FEDER (European Fund for Regional Development)-COMPETE-QRENEU for financial support through the research units Chemistry Research Centre of (UID/QUI/00686/2020). This work was carried out in part using the Advanced Electron Microscopy, Imaging and Spectroscopy (AEMIS) Facilities available at INL. I. Amorim is thankful to Fundação para a Ciência e Tecnologia (FCT) for the support of PhD grant No. SFRH/BD/137546/2018, co-financed by the Fundo Social Europeu (FSE) through the Programa Operacional Regional Norte (Norte 2020) under Portugal 2020

Facile preparation of a Pt-ERGO composite modified screen-printed electrode for the sensitive determination of phenolic compounds

The mass production of screen-printed electrochemical devices with integrated electrodes has facilitated the widespread adoption of electroanalytical methods. The SPEs (screen-printed electrodes) overcome some obstacles associated with the use of conventional electrochemical cells, making them accessible to untrained operators. Despite their advantages, SPEs require activation/modification of the working electrode (WE) to enhance sensitivity. Nanomaterials, with metal nanoparticles (NPs) dispersed in polymers and/or carbon NPs has gaining popularity for this purpose. In this study, we describe a modification of carbon SPEs (SPCEs) using Pt NPs and reduced graphene oxide (ERGO). The Pt-ERGO@SPCE is prepared by galvanostatic reduction of drop-casted precursors directly onto the WE surface, eliminating complex synthetic steps and high temperatures. After optimizing Pt amount and reduction extent, the modified SPCEs were tested for detecting hydroquinone (HQ) and bisphenol A (BPA). DPV results show significantly increased sensitivity for the quantification of both compounds. The modified SPCEs demonstrates promising performance: precision (5 % HQ, 8 % BPA), detection limits (1.4 μM HQ, 4.6 μM BPA), sensitivity (1688 μA mM−1 HQ, 441 μA mM−1 BPA), and recoveries (98–113 % HQ, 98–104 % BPA). This simple electrode modification holds great potential, allowing the preparation of the sensor by personnel who may lack access to well-equipped laboratories, particularly in developing countries

Facile preparation of a Pt-ERGO composite modified screen-printed electrode for the sensitive determination of phenolic compounds

The mass production of screen-printed electrochemical devices with integrated electrodes has facilitated the widespread adoption of electroanalytical methods. The SPEs (screen-printed electrodes) overcome some obstacles associated with the use of conventional electrochemical cells, making them accessible to untrained operators. Despite their advantages, SPEs require activation/ modification of the working electrode (WE) to enhance sensitivity. Nanomaterials, with metal nanoparticles (NPs) dispersed in polymers and /or carbon NPs has gaining popularity for this purpose. In this study, we describe a modification of carbon SPEs (SPCEs) using Pt NPs and reduced graphene oxide (ERGO). The Pt-ERGO@SPCE is prepared by galvanostatic reduction of drop-casted precursors directly onto the WE surface, eliminating complex synthetic steps and high temperatures. After optimizing Pt amount and reduction extent, the modified SPCEs were tested for detecting hydroquinone (HQ) and bisphenol A (BPA). DPV results show significantly increased sensitivity for the quantification of both compounds. The modified SPCEs demonstrates promising performance: precision (5% HQ, 8% BPA), detection limits (1.4 µM HQ, 4.6 µM BPA), sensitivity (1688 µA mM-1 HQ, 441 µA mM-1 BPA), and recoveries (98-113% HQ, 98-104% BPA). This simple electrode modification holds great potential, allowing the preparation of the sensor by personnel who may lack access to well-equipped laboratories, particularly in developing countriesThanks are due to Fundação para a Ciência e Tecnologia (FCT), Portugal and FEDER (European Fund for Regional Development)-COMPETE-QRENEU for financial support through the research units Chemistry Research Centre of (UID/QUI/00686/2020). L. Lema is thankful to the Angolan Government, MESCT and ISCED of Uíge for the support of PhD grant

Template-Free Synthesis of Hollow Iron Phosphide–Phosphate Composite Nanotubes for Use as Active and Stable Oxygen Evolution Electrocatalysts

The oxygen evolution reaction (OER) is a half-cell reaction that is of importance to many electrochemical processes, especially for electrochemical and photoelectrochemical water splitting. Developing efficient, durable, and low-cost OER electrocatalysts comprising Earth-abundant elements has been in the focus of electrocatalysis research. Herein, we report a cost-effective, scalable, and template-free approach to the fabrication of hollow iron phosphide–phosphate (FeP–FeP_<i>x</i>O_<i>y</i>) composite nanotubes (NTs), which is realized by hydrothermal growth of iron oxy-hydroxide nanorods (NRs) and a subsequent postphosphorization treatment. The hollow interior of NTs results from the Kirkendall effect occurring upon phosphorization. When used to catalyze the OER in basic medium, the as-synthesized FeP–FeP_<i>x</i>O_<i>y</i> composite NTs exhibit excellent catalytic activity, delivering the benchmark current density of 10 mA cm^–2 at a low overpotential of 280 mV and showing a small Tafel slope of 48 mV dec^–1 and a high turnover frequency of 0.10 s^–1 at the overpotential of 350 mV. Moreover, the composite NTs demonstrate outstanding long-term stability, capable of catalyzing the OER at 10 mA cm^–2 for 42 h without increasing the overpotential, holding substantial potential for use as active and inexpensive anode catalysts in water electrolyzers

Espetroscopia de RMN em estudos de relação estrutura-atividade de péptidos antimicrobianos

Comunicação em painel P41A técnica de RMN tem sido muito útil nos estudos de relação estrutura-atividade dos péptidos antimicrobianos, pois é possível averiguar qual é a ligação entre as preferências conformacionais dos péptidos e a sua atividade ao nível da capacidade de disrupção das membranas celulares ou as suas interações com as mesmas