# Molecular Design Strategy of π‐Conjugated Polymers for Efficient Visible‐Light‐Driven Photoelectrocatalytic O2 Reduction to H2O2 Production

## TL;DR

Scientists designed a new polymer to efficiently produce hydrogen peroxide using visible light, improving sustainability and efficiency.

## Contribution

A new molecular design strategy for π-conjugated polymers was developed to enhance visible-light-driven H2O2 production.

## Key findings

- Replacing phenyl with naphthalene units in polymers deepened the HOMO energy level, increasing photoelectrocatalytic activity.
- The PBTN thin film achieved a 1.47 times higher H2O2 production rate than PBTB with 99% efficiency and selectivity.
- Visible-light-assisted PBTN achieved a high H2O2 production rate of 128 mmol/gphotocathode.

## Abstract

Toward sustainable hydrogen peroxide (H2O2) production, photo(electro)catalytic oxygen (O2) reduction/H2O2 production has attracted increasing attention. Recently, we have found that a thin film of the π‐conjugated polymer, poly(1,4‐bis(2‐thienyl)benzene) (PBTB), exhibits exceptionally high (photo)electrocatalytic activity for O2 reduction/H2O2 production. To achieve higher photoelectrocatalytic activity and efficient visible‐light‐driven photoelectrocatalytic H2O2 production, we investigated the molecular design related to the highest occupied molecular orbital (HOMO) energy level (E
HOMO) of these polymers. We designed and synthesized poly(1,4‐bis(2‐thienyl)naphthalene) (PBTN), in which replacing the phenyl unit of PBTB with a naphthalene unit—a stronger electron‐withdrawing group—and increasing the polymer chain twist angle selectively deepened E
HOMO relative to PBTB. The degree of E
HOMO deepening quantitatively affected the onset potential of PBTN. Under visible‐light irradiation and 0 V vs. Ag/AgCl, the PBTN thin film achieved a high O2 reduction/H2O2 production rate (1.11 × 103 
mmolH2O2/gphotoelectrocatalyst), 1.47 times higher than that of PBTB, with excellent Coulombic efficiency (99%) and selectivity (99%). The onset potential of PBTN for visible‐light‐assisted O2 reduction enabled a photocatalytic H2O2 production setup. Upon visible‐light irradiation, this setup achieved a high photocatalytic O2 reduction/H2O2 production rate of 128 mmolH2O2/gphotocathode. These results clearly demonstrate the tunability of the photoelectrocatalytic activity of π‐conjugated polymers through E
HOMO‐related molecular design.

This study demonstrated the high tunability of the photoelectrocatalytic activity of π‐conjugated polymer thin films for oxygen (O2) reduction/hydrogen peroxide (H2O2) production through molecular design. The degree of HOMO energy level deepening quantitatively affected the onset potential for light‐assisted O2 reduction toward more positive values, enhancing the photoelectrocatalytic H2O2 production rate.© 2026 WILEY‐VCH GmbH