Phthalocyanine Polymer Anchored Ketjen Black Nanoparticles for Bifunctional Oxygen Electrocatalysis

• Published in: ACS applied nano materials Vol. 7; no. 9; pp. 10600 - 10613
• Main Authors: Kousar, Naseem, Thimmappa, Ravikumar, Giddaerappa, Palanna, Manjunatha, Sannegowda, Lokesh Koodlur
• Format: Journal Article
• Language: English
• Published: American Chemical Society 10.05.2024
• Subjects: Ketjen black; oxygen evolution reaction; Tafel slope; exchange current density; adsorbate evolution mechanism; cobalt phthalocyanine polymer; oxygen reduction reaction; density function theory
• ISSN: 2574-0970; 2574-0970
• DOI: 10.1021/acsanm.4c01044

The limitations of current benchmark oxygen electrocatalysts, such as RuO2, IrO2, and Pt/C, due to their high cost, scarcity, and unifunctionality, have inspired a search for more effective oxygen catalysts to advance sustainable enegry solutions. Hence, development of cost-effective bifunctional catalysts to overcome the issues associated with benchmark catalysts is crucial. Metal–organic framework composites containing conductive carbon materials present promising solutions to these challenges. This study reports the synthesis, characterization, and application of a metal–organic framework of cobalt­(II) tetra­(3-hydroxy tyramine) phthalocyanine polymer, poly­[Co (II) THTPc], for bifunctional oxygen electrocatalysis. The synthesis methodology is simple, cost-effective, and sustainable. To improve the catalytic performance of poly­[Co (II) THTPc], an organic-hybrid composite was prepared by incorporating Ketjen black (KB) nanoparticles at an optimized ratio. The resulting poly­[Co (II) THTPc]:KB (4:1, respectively) hybrid exhibited outstanding catalytic activity for OER bearing an overpotential of 359 mV on a Ni foam substrate and 371 mV on a glassy carbon electrode (GCE) substrate at 10 mA cm–2 current density in 1.0 M KOH at 5 mV s–1 scan rate. Furthermore, the same composite catalyst demonstrated an onset potential of 0.876 V vs RHE for ORR with a half-wave potential of 0.767 V vs RHE, obeying four-electron-transfer pathway in the same electrolyte and scan rate on GCE. In addition, the designed hybrid catalyst demonstrated improved catalytic properties compared to standard catalysts, including a lower Tafel slope, reduced charge-transfer resistance, and higher exchange current density for OER and ORR. The remarkable catalytic performance of the developed hybrid can be attributed to various synergistic effects, favorable π–π interactions, and increased number of electroactive sites that downshifts the D-band center of Co adsorption sites, effectively reducing the activation barrier of reaction intermediates in both the OER and ORR. Importantly, the low-cost bifunctional oxygen catalyst exhibited excellent stability and efficiency, making it a potential bifunctional oxygen electrocatalyst for large-scale integrated green energy systems.