Yanan Chang, Xuyun Lu, Qiao Tan, Jianing Li, Yawen Tang, Jianchun Bao, Ying Liu, Chao Ma, Gengtao Fu

Abstract

The construction of highly active sites and the simultaneous establishment of photothermal/photoelectronic phases represent an emerging paradigm for boosting small-molecule-assisted water splitting. Herein, we report an effective Sn2+-initiated phase-modulation strategy for the facile synthesis of a photothermal/photoelectronic phase with rhombohedral NiSe and Ni3Se2 (r-NiSe/r-Ni3Se2) as a precursor. The strategy drives an in situ phase transition of r-NiSe to hexagonal NiSe (h-NiSe), along with the generation of orthorhombic SnSe (o-SnSe), ultimately forming the multifunctional heterostructure o-SnSe/h-NiSe/r-Ni3Se2. Theoretical calculations reveal that h-NiSe lowers the urea oxidation reaction (UOR) energy barrier relative to r-NiSe (0.745 eV vs. 0.901 eV), while the o-SnSe enhances both light harvesting and photothermal/photoelectronic functionalities of the o-SnSe/h-NiSe/r-Ni3Se2. Unlike traditional UOR electrocatalysts, its photothermal effect promotes urea adsorption, offsets the endothermic enthalpy of UOR, and accelerates electron/mass-transfer kinetics. Concurrently, the photoelectronic effect enhances the charge-carrier density from 1.4 × 1024 to 4.2 × 1024 cm−3, lowers the UOR activation energy from 48.4 to 9.7 kJ mol−1. Capitalizing on these synergistic advantages, the o-SnSe/h-NiSe/r-Ni3Se2 delivers exceptional UOR activity, achieving 10, 500, and 1000 mA cm−2 at merely 1.28, 1.34, and 1.37 V, respectively. When implemented in a urea-assisted water splitting electrolyzer, the o-SnSe/h-NiSe/r-Ni3Se2||o-SnSe/h-NiSe/r-Ni3Se2 device requires only 1.34 and 1.79 V to sustain 100 and 500 mA cm−2, respectively, outperforming the conventional HER||OER electrolyzer (1.61 and 1.99 V).

Paper Linkage:https://doi.org/10.1002/adma.202519855