Green hydrogen production via a photocatalyst-enabled optical fiber system: A promising route to net-zero emissions

Abstract

Achieving zero emissions is a critical goal in combating climate change. Hydrogen is a versatile energy carrier contributing to this objective. Green hydrogen production via photocatalytic (PC) and photoelectrochemical (PEC) water splitting is promising due to its potential to utilize renewable energy (direct solar, photovoltaics, wind, hydropower). However, current PC and PEC water splitting systems face challenges such as low light utilization efficiency and high operational costs related to both catalyst selection and reactor designs. This study presents a novel photocatalytic hydrogen production system, POF-STO, by attaching a modified strontium titanate (STO) onto thin polymer optical fibers (POF). Light launched from 365 nm LED into the POF lumen is side-emitted and excites STO in a porous layer on the POF surface. This PC system improves upon our previous PEC-POF-ITO/g-C₃N₄ system, which required dual nanoparticles of indium tin oxide (ITO) to make the POF optoelectrodes conductive plus graphitic carbon nitride (g-C₃N₄) photocatalysts. Our innovative inside-out light delivery mechanism with the POF ensures efficient photon confinement and energy transfer to the STO surface, maximizing light utilization. The chemically stable STO with up to 7-fold H₂ production rates than the PEC-POF-ITO/g-C₃N₄ system was observed. Our POF-STO system produced stable H₂ production rates in both acidic and alkaline environments, with <10 % reduction in hydrogen generation when using tap water and seawater. Eliminating complex electrical setups, potentiostats, electrodes, and aqueous electrolytes significantly reduces system costs. Using bundles with multiple POF-STOs and utilizing heat from LEDs allowed operation at higher water temperatures, further increasing H₂ production efficiency. Compared with other reactor designs, the POF-STO emerges as an innovative approach with potential to achieve ambitious global net-zero emission goals.