Fe Cluster Modified Co 9 S 8 Heterojunction: Highly Efficient Photoelectrocatalyst for Overall Water Splitting and Flexible Zinc-Air Batteries.

Designing bifunctional low-cost photo-assisted electrocatalysts for converting solar and electric energy into hydrogen energy remains a huge challenge. Herein, we demonstrate a heterojunction (Fe cluster modified Co 9 S 8 ) for both hydrogen evolution reaction (HER) and oxygen evolution reaction (OER). Benefiting from the good electronic conductivity and spatial confinement of the N-doped carbon skeleton, as well as the electronic structure regulation of the Fe cluster, Co 9 S 8 -Fe@CNT exhibits excellent catalytic performance with a low overpotential of 150 mV for OER and 135 mV for HER at a current density of 10 mA cm -2 . Upon light irradiation, holes and electrons are generated in the valence band and conduction band of the Co 9 S 8 , respectively. Part of the charges are transferred to the interface to facilitate the catalytic reaction, while the remaining are transferred by the electrode. When working as a bifunctional catalyst for overall water splitting, the performance can reach 1.33 V at 10 mA cm -2 under light conditions, which is significantly better than 1.52 V in a dark environment. Theoretical calculations revealed lowered Gibbs free energy (∆G H *) of the heterojunction with the effect of Fe modification of Co 9 S 8 . This work sheds a new light in designing novel photoelectrochemical materials to convert solar energy and electric energy into chemical energy. This article is protected by copyright. All rights reserved.