Desenvolvimento de eletrocatalisadores de platina modificados por adátomos do bloco p para a conversão eletroquímica de glicerol em meio alcalino

Author(s)

Matheus Batista Cordeiro de Souza

• Document type: Doctoral Thesis
• Press: Campinas, SP.
• Institution: Universidade Estadual de Campinas (UNICAMP). Instituto de Química
• Defense date: 2022-10-25

Examining board members

Pablo Sebastián Fernández; Cláudia Longo; William Reis de Araujo; Camilo Andrea Angelucci; José Joaquín Linares León

• Advisor: Pablo Sebastián Fernández

Abstract

Alternatives to the current dependency on fossil fuels are constantly sought after, as it is the only way to minimize the current impact of global warming effect. High-purity hydrogen gas is unanimously considered an important renewable energy source in the foreseeable future, and it can be sustainably synthesized from water electrolysis. Of the many issues surrounding water electrolysis, substituting the anode reaction (oxygen evolution) for biomass oxidation, like the glycerol oxidation, not only would decrease the energy cost needed to operate these devices, but would also enable the generation of value-added products from the biomass conversion. Glycerol is readily obtained as a byproduct from the biodiesel synthesis, another renewable fuel source widely used in the transportation sector, and glycerol itself can also be used as an energy source by its direct oxidation, with the added possibility of generating green hydrogen, in addition to its conversion into other value-added molecules. In this context, this work aims to develop platinum-based catalysts for the electrochemical oxidation of glycerol in alkaline media, and later apply the acquired knowledge to electrochemical devices. In an initial electrochemical investigation, we modified the electrodes with nine different elements from the p-block and identified three elements that improved the electrode activity when compared to the clean platinum electrode: lead, bismuth, and thallium. The addition of these elements resulted in higher anodic currents for a longer period. Using in situ FTIR, we showed that the presence of adatoms reduced the cleavage of C-C bonds during the oxidation, and prevented the adsorption of CO, a poisonous intermediate. Soluble oxidation products were identified using liquid chromatography, and while the selectivity of the reaction did not change, there was a significant increase in the reaction yield. Lastly, we were able to transfer the resulting knowledge to a glycerol-based microfluidic fuel cell, where we modified the anode, Pt/C nanoparticles supported on carbon paper, with bismuth. We saw a significant increase in the open circuit voltage and power extracted from the device after modification, and a mixture of glycolate and formate was generated in the exhaust electrolyte, confirming the possibility of the cogeneration of energy with value-added chemicals (AU)

• FAPESP's process: 19/00305-2 - Development of p-block adatom-modified platinum electrocatalysts for the electrochemical conversion of glycerol in alkaline medium
• Grantee: Matheus Batista Cordeiro de Souza
• Support Opportunities: Scholarships in Brazil - Doctorate