Bio-inspired electroactive polymeric benzimidazole phthalocyanine: a sustainable electrocatalyst for enhanced hydrogen evolution reaction

Abstract

The sustainable energy production from renewable sources is of crucial interest in the current scenario, with a focus on harnessing solar, wind, geothermal, and tidal energy systems. Water emerges as a significant resource, for converting the chemical energy into hydrogen fuel and oxygen through water electrolysis. To achieve sustainable hydrogen production, the development of eco-friendly and cost-effective electrocatalysts is important. In this direction, the polymeric-[cobalt(II) tetrabenzoxybenzimidazole phthalocyanine], poly[Co(II)TBBImPc] is synthesized and characterized using various spectroscopic techniques to confirm its formation and purity. Microscope images confirmed the uniform distribution of the polymeric film on the surface. The electrochemical activity of poly[Co(II)TBBImPc] as an electrocatalyst is evaluated for the HER and the results demonstrated promising lower overpotential at a current density of −10 mA cm⁻² in 0.5 M H₂SO₄. Further improvement in electrochemical activity is achieved by forming a hybrid with conducting Ketjen Black (KB), resulting in poly[Co(II)TBBImPc]+KB. Linear sweep voltammetry (LSV) measurements ensured a shift in the HER onset potential towards positive potential in the hybrid which is attributed to the increased electrochemical activity of poly[Co(II)TBBImPc]+KB. The composite demonstrated a low overpotential of −0.190 V to attain −10 mA cm⁻². In comparison, Pt/C and poly[Co(II)TBBImPc] displayed overpotentials of −0.067 V and −0.456 V, respectively, to achieve −10 mA cm⁻². Chronoamperometric measurements revealed the excellent stability of the fabricated poly[Co(II)TBBImPc]+KB hybrid for the HER. The superior activity of the composite may be due to the electronic modulation and decrease in the energy band center. These results emphasize the potential of this low-cost, non-precious composite as an outstanding catalyst for the HER, presenting an opportunity to reduce reliance on precious metal alloys and complex materials in water electrolysis for hydrogen production.