120th General Meeting of the KCS

Type Symposium
Area Current Trends in Electrochemistry for Energy Conversion
Room No. Room 201+202
Time THU 13:55-:
Code ELEC1-2
Subject High efficiency oxygen evolution from water using elaborately designed hematite photoanodes
Authors Hyunwoong Park
School of Energy Engineering, Kyungpook National University, Korea
Abstract Molecular hydrogen (H2) produced via solar water splitting has received growing attention as a renewable and carbon-neutral energy carrier over the past four decades. To drive high-efficiency solar H2 production, significant effort has been focused on photoelectrochemical (PEC) water oxidation, particularly in terms of reducing overpotential while increasing photocurrents for the oxygen evolution reaction (OER) at E = 1.23 V. Among the many semiconductor photoanode materials reported in the literature, hematite (alpha-Fe2O3) is considered the most suitable. However, hematite suffers from poor solar-to-hydrogen (STH) efficiency (i.e., small photocurrent densities at 1.23 V) and rapid deactivation, primarily because of its short hole-diffusion length (2-4 nm), rapid charge recombination, sluggish charge transfer, and inefficient charge injection. These challenges have been traditionally addressed by adopting problem-specific strategies including doping, passivation, and coupling with OER catalysts. Nevertheless, the PEC performance of hematite is still poor in terms of photocurrent and durability. Herein, we report the synthesis of ultra-highly efficient and durable hematite nanorod arrays developed by elaborate engineering and careful optimization of three surface modification methods, i.e., hydrogen treatment, coating with a TiO2 passivation layer, and deposition of cobalt phosphate OER catalyst. Each modification significantly affected the PEC performance, while integration of all three modifications led to unprecedented photocurrents of ~6 mA/cm2 at 1.23 V over 100 h under simulated sunlight (AM 1.5G, 100 mW/cm2). The Faradaic efficiency of O2 evolution was over 95%, and a stoichiometric amount of H2 was simultaneously produced.
E-mail hwp@knu.ac.kr