Narisara Tanjedrew, Kittimeth Thammanatpong, Panida Surawatanawong, Pongkarn Chakthranont, Teera Chantarojsiri, Takdanai Unjarern, and Supavadee Kiatisevi*

Three bioinspired metal-free imidazole-benzimidazole electrocatalysts with different substituents (ImBenz-H, ImBenz-NO₂, ImBenz-OCH₃) were prepared to fine-tune their catalytic activity toward the oxygen reduction reaction (ORR) in neutral (pH 7) and alkaline (pH 13) solutions. The RRDE and CV experiments revealed that ImBenz-NO₂, with its electron-withdrawing group, has high selectivity for H₂O at pH 7. In contrast, ImBenz-H, without a substituent, showed the highest selectivity for H₂O₂ at pH 13 with the highest turnover frequencies (TOFs, 10³ s^–¹) at both pH levels. Density functional theory (DFT) calculations suggest that the ORR mechanism for ImBenz-H involves electron transfer from imidazole-benzimidazole to O₂, forming H₂O₂ as the first product, which supports the redox-active properties of the ImBenz catalysts. These electrochemical and DFT studies support that the ORR selectivity can be adjusted by changing the substituent on the ImBenz catalysts.

Thanks to Mahidol University under the New Discovery and Frontier Research Grant and NSRF via the Program Management Unit for Human Resources & Institutional Development, Research and Innovation [grant number B40G660031].