Decreased energy barrier and improved interfacial kinetics for efficient photoelectrochemical water splitting using La-engineered LDHs coupled with BiVO4

Abstract

Potential of photoelectrochemical (PEC) water splitting is significantly constrained by the slow kinetics of the interfacial oxygen evolution reaction (OER). While co-catalyst engineering offers a promising approach to enhance sluggish OER kinetics, progress in this field is still hampered by limited carrier transfer process and severe carrier recombination. To address these issues, we introduced the rare earth element La via a simple hydrothermal method and loaded Co₂Fe_xLa_1−x layered double hydroxides (LDHs) on the surface of BiVO₄ as an efficient co-catalyst. Co₂Fe_xLa_1−x-LDHs accelerated the transfer of the photogenerated holes, along with improved interfacial overpotential and decreased reaction barrier. Simultaneously, the addition of La optimized electronic properties, significantly improving catalytic performance. Co₂Fe_0.2La_0.8-LDHs/BiVO₄ exhibited a high photocurrent density of 5.8 mA cm⁻² at 1.23 V vs. RHE. Additionally, it demonstrated excellent stability, maintaining a photocurrent density of 5.3 mA cm⁻² after 5 hours, which is 95.3% of the initial value. Combining operando characterizations with theoretical calculations, it was evaluated that the presence of La can notably decrease the energy barrier for key intermediates and accelerate the transformation process to the ˙O₂⁻ intermediate. This study provides a feasible approach to preparing low-cost, high-performance solar water decomposition catalysts and explores the specific role of La.