Modified Poly(Heptazine Imides): Minimizing H2O2 Decomposition to Maximize Oxygen Reduction

Author(s)

Rogolino, Andrea ; Silva, Ingrid F. ; Tarakina, Nadezda V. ; da Silva, Marcos A. R. ; Rocha, Guilherme F. S. R. ; Antonietti, Markus ; Teixeira, Ivo F.

• Document type: Journal article
• Source: ACS APPLIED MATERIALS & INTERFACES; v. 14, n. 44, p. 10-pg., 2022-10-31.

Abstract

Photocatalysis provides a sustainable pathway to produce the consumer chemical H2O2 from atmospheric O2 via an oxygen reduction reaction (ORR). Such an alternative is attractive to replace the cumbersome traditional anthraquinone method for H2O2 synthesis on a large scale. Carbon nitrides have shown very interesting results as heterogeneous photocatalysts in ORR because their covalent two-dimensional (2D) structure is believed to increase selectivity toward the two-electron process. However, an efficient and scalable application of carbon nitrides for this reaction is far from being achieved. Poly(heptazine imides) (PHIs) are a more powerful subgroup of carbon nitrides whose structure provides high crystallinity and a scaffold to host transition-metal single atoms. Herein, we show that PHIs functionalized with sodium and the recently reported fully protonated PHI exhibit high activity in two-electron ORR under visible light. The latter converted O2 to up to 1556 mmol L-1 h-1 g-1 H2O2 under 410 nm irradiation using inexpensive but otherwise chemically demanding glycerin as a sacrificial electron donor. We also prove that functionalization with transition metals is not beneficial for H2O2 synthesis, as the metal also catalyzes its decomposition. Transient photoluminescence spectroscopy suggests that H-PHIs exhibit higher activity due to their longer excited-state lifetime. Overall, this work highlights the high photocatalytic activity of the rarely examined fully protonated PHI and represents a step forward in the application of inexpensive covalent materials for photocatalytic H2O2 synthesis. (AU)

• FAPESP's process: 21/11162-8 - Multi-user equipment approved in grant 2020/14741-6: GC-MS/FID/TCD (2 injetores+Loop+Sistema valvulado)
• Grantee: Ivo Freitas Teixeira
• Support Opportunities: Multi-user Equipment Program
• FAPESP's process: 20/14741-6 - Graphitic carbon nitrides as platforms for single-atom photocatalysis: moving towards design principles for improved performance
• Grantee: Ivo Freitas Teixeira
• Support Opportunities: Research Grants - Young Investigators Grants
• FAPESP's process: 22/04748-9 - Graphitic carbon nitrides as acid solid catalysts applied to biomass conversion
• Grantee: Guilherme de Freitas Silva Rodrigues Rocha
• Support Opportunities: Scholarships in Brazil - Master
• FAPESP's process: 21/13271-9 - Single atoms coordinated on graphitic carbon nitrides to photocatalytic conversion of methane
• Grantee: Marcos Augusto Ribeiro da Silva
• Support Opportunities: Scholarships in Brazil - Doctorate