Electrogeneration of Hydrogen Peroxide in Acid Medium using Pyrolyzed Cobalt-based Catalysts: Influence of the Cobalt Content on the Electrode Performance

Abstract

Cobalt tetramethoxyphenyl porphyrin (CoTMPP) adsorbed on a high area carbon support (Vulcan XC72-R) and heat-treated at 900°C under inert atmosphere was studied as electrocatalyst for the reduction of O 2 to H 2 O 2 in acid medium. Experiments performed on rotating ring-disc electrode (RRDE) and gas diffusion electrode (GDE) show that the catalyst performance depends on the cobalt loading, going through a maximum at 0.2 wt. % Co. For higher cobalt loadings, a growing part of oxygen is reduced into water, decreasing therefore the selectivity of the catalyst. These results are interpreted in terms of a further reduction of H 2 O 2 on Co-based catalytic sites before leaving the catalytic layer. For a GDE polarized at )150 mV vs. saturated calomel electrode (SCE) and loaded with 0.9 lg cm )2 of 0.2 wt. % Co-based catalyst, a H 2 O 2 production rate of 300 lmol h )1 cm )2 was obtained which is five times higher than the H 2 O 2 production rate measured with Vulcan. In these conditions, the selectivity of the Co-based catalyst for H 2 O 2 production is 92%. The good agreement observed between RRDE and GDE results confirms the relevance of using RRDE experiment for screening these non-precious metal catalysts for further GDE applications.

Nonprecious metal catalysts for the molecular oxygen‐reduction reaction

“…In the case of CoTMPP/Vulcan XC72-R, the catalyst performance depends on the Co loading, going through a maximum at 0.2% Co [104].…”

Analysis of Adsorption Effects on a Metal-Nitrogen-Carbon Catalyst Using a Rotating Ring-Disk Study

“…Previous RRDE studies of non-precious metal catalysts for oxygen reduction 1,[12][13][14][15][16][17] generally show an increase in peroxide generation by one to two percent per 0.1 mg/cm 2 decrease in loading. 1,13,17,18 This suggests that peroxide detection at the ring could be artificially low because inner layers may further reduce peroxide to water, decreasing peroxide at the ring and increasing total disk current.…”

“…1,13,17,18 This suggests that peroxide detection at the ring could be artificially low because inner layers may further reduce peroxide to water, decreasing peroxide at the ring and increasing total disk current. Additionally, more active catalysts have been found to produce less peroxide; this is found both by varying metal content 14 and morphology of the carbon support. Such considerations motivate the need for increased understanding of the ORR mechanism using MNC catalysts.…”

Desenvolvimento e avaliação de eletrodos de difusão gasosa (EDG) para geração de H2O2 in situ e sua aplicação na degradação do corante reativo azul 19

“…21,22 A utilização de EDG em processos eletroquímicos, além de gerar catodicamente o H 2 O 2 , permite também trocar a reação cató-dica, normalmente representada pela reação de desprendimento de hidrogênio (Equação 1), pela reação de redução do oxigênio (Equação 2), com isso, pode-se deslocar o potencial de equilíbrio do catodo em até 1,2 V na direção mais positiva de potencial, implicando em uma diminuição da mesma ordem na diferença de potencial entre o catodo e o anodo. 24 [25][26][27] O uso do peróxido de hidrogênio no tratamento de águas contaminadas é comumente conhecido, porém com as dificuldades de transporte e armazenamento desta substância, principalmente devido as suas características químicas, [10][11][12][13] o uso dos eletrodos de difusão gasosa se mostra uma alternativa viável para a produção in situ do H 2 O 2 , eliminando assim a necessidade de transporte e armazenagem. Essa implementação na geração do H 2 O 2 no local de consumo é muito importante, pois em alguns ramos industriais é necessário o uso de elevado volume desse reagente para o tratamento dos efluentes; um exemplo deste ramo é a indústria têxtil.…”