Research progress on efficient and selective transition metal oxides for photoelectrochemical seawater splitting

Abstract

Harnessing solar energy through photochemical processes in seawater offers a promising path toward sustainable hydrogen production. Photoelectrochemical (PEC) seawater splitting combines light-driven charge separation with abundant water resources to generate hydrogen fuel. This review highlights recent progress in transition metal oxide (TMO) photoanodes and nickel (Ni)-based cocatalysts, focusing on the interplay of light absorption, charge transport, and surface catalysis. Titanium dioxide exhibits excellent photochemical stability but limited visible-light response (<1 mA cm - 2 ). Tungsten trioxide and hematite extend light absorption, reaching ~6 and ~4 mA cm -2 , respectively, though both face charge recombination and stability challenges. Bismuth vanadate, with a 2.4 eV bandgap, currently shows the best balance, achieving 4-7 mA cm -2 at 1.23 V vs. RHE when coupled with protective layers and cocatalysts. Meanwhile, NiMoand NiFe-based cocatalysts offer cost-effective enhancement of interfacial charge transfer and corrosion resistance.Despite these advances, long-term durability in chloride-rich environments and scalable fabrication remain major hurdles. Future breakthroughs will rely on integrating photochemical optimization, protective architectures, and hybrid PECelectrolyzer strategies to enable practical, large-scale seawater splitting. By linking fundamental photochemistry with device-level performance, this review provides insight into designing efficient and robust PEC systems for solar hydrogen production.