Design of Electrocatalysts and System for Water Electrolysis

Electrochemical water splitting is considered an attractive strategy for generating high-purity green hydrogen, which could support global energy supply and carbon neutrality goals. Yet, its large-scale adoption is still restricted by slow electrode kinetics, catalyst instability, and limited integration with renewable energy systems. The hydrogen evolution reaction (HER) and oxygen evolution reaction (OER), which occur at the cathode and anode respectively, require efficient, stable, and cost-effective electrocatalysts, particularly under harsh acidic or saline conditions. Moreover, the integration of electrolysis with solar energy to form photovoltaic-electrolysis (PVE) systems is critical for maximizing solar-to-hydrogen (STH) efficiency under practical current densities. To address these multifaceted challenges, this thesis focuses on the rational design of advanced electrocatalysts and system-level engineering strategies for high-performance green hydrogen production. First, a binary structure Pt-Fe3O4/NC catalyst is developed for HER in acidic media, achieving low overpotential and enhanced mass activity due to electronic modulation and interfacial synergy between Pt and Fe3O4. Second, to address the issue of catalyst degradation in saline environments, a hierarchically assembled S-NiFeOx/FeS electrode is fabricated for alkaline seawater OER. The sulfur-modulated multilayer architecture enables both surface crystallinity control and in situ self-reconstruction, resulting in high current density (≥500 mA cm-2) and long-term durability (>100 h) in saline conditions. Third, a high-efficiency PVE system is constructed by coupling a triple-junction CPV module with a zero-gap alkaline water electrolyser, employing Fe2O3-NiOxHy OER electrodes. This system demonstrates an STH efficiency exceeding 30% at industrially relevant current densities, verified under real sunlight. Together, these studies provide mechanistic insights and design strategies for electrocatalysts and systems across diverse electrolysis scenarios-including proton exchange membrane (PEM), anion exchange membrane (AEM), and photovoltaic-alkaline water electrolysis (PV-AWE) configurations, thus paving the way toward practical, scalable, and efficient green hydrogen production.