Dual-functional atomic layer graphene enable bias-free photoelectrochemical iodide oxidation reaction for seawater splitting
Journal
Carbon
Journal Volume
249
Start Page
121250
ISSN
00086223
Date Issued
2026-02-10
Author(s)
Huang, Yung-Hung
Wu, Po-Hsien
Lu, Yang-Sheng
Lin, Yin-Cheng
Huang, Chih-Ying
Yu, Cheng-Yu
Cyue, Zih-Wei
Lin, Jou-Chun
Chang, Chun-Chih
Li, Shao-Sian
Hwang, Bing Joe
Wang, Di-Yan
Abstract
Bias-free photoelectrochemical (PEC) seawater splitting has emerged as an attractive technology for solar-to-hydrogen (STH) conversion. This work demonstrates a promising alternative by replacing the sluggish kinetics of the oxygen evolution reaction (OER) with iodide oxidation reaction (IOR), which requires a much lower oxidation potential of 0.53 V vs. RHE. This approach facilitates bias-free solar-to-hydrogen (STH) conversion directly from natural seawater while simultaneously producing high-value triiodide (I3−) chemicals. An atomic layer of graphene functions as an efficient catalyst for PEC IOR when integrated with a Si heterojunction photoanode, exhibiting a promising PEC IOR with a low onset potential of 0.05 V vs. RHE. The unique two-dimensional energy dispersion and delocalized π-electrons of graphene facilitate rapid charge transfer, thereby enhancing overall catalytic efficiency. In-situ Raman spectroscopic analysis was performed to manifest that In-situ Raman spectroscopy reveals that adsorbed iodide/iodine species will induce local lattice strain in graphene, which perturbs the coherence of phonon scattering in the π-system. Moreover, when coupled with a Pt/graphene/Si heterojunction photocathode for HER, a bias-free PEC system for STH and IOR can be simultaneously achieved. This system demonstrates remarkable performance and stability, yielding a high photocurrent density of 14.22 mA/cm2 for simulated seawater and 13.13 mA/cm2 for natural seawater without any applied bias under 1 sun illumination. The integrated graphene/Si heterojunction photoelectrodes provide a promising platform for developing stable and high-performance bias-free PEC cells, facilitating simultaneous STH conversion and producing valuable chemicals from seawater.
Subjects
Atomic layer graphene catalysts
Bias-free solar to hydrogen conversion
EVA graphene transfer method
Iodide oxidation reaction
Photoelectrochemical cell
Publisher
Elsevier Ltd
Type
journal article