Comparative study of zinc sulfide, tin selenide, and their composite electrocatalysts for oxygen evolution reaction: Towards efficient and stable water splitting

Abstract

Oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) are critical processes in electrochemical water splitting, driving demand for efficient and durable electrocatalysts. This study presents a comprehensive evaluation of water splitting performance of ZnS@SnSe₂ nano–composite in 1.0 M KOH solution. With ZnS nanoparticles decorated on SnSe₂, exhibited remarkable catalytic activity for both HER and OER. ZnS@SnSe₂ composite demonstrated an low overpotential of 22 mV to reach a current density of 10 mA cm^-2, outperforming ZnS (245 mV) and SnSe₂ (280 mV). Furthermore, it achieved a Tafel slope of 25 mV dec^‑1 and a charge transfer resistance (Rct) of 5.2 Ω, reflecting its enhanced kinetics compared to ZnS (101 mV dec^‑1, Rct = 35 Ω) and SnSe₂ (230 mV dec^‑1, Rct = 7.5 Ω). These results are even competitive with benchmark Pt/C catalyst (30 mV overpotential, 46 mV dec^‑1, and 2.2 Ω Rct), highlighting efficiency of composite for hydrogen production. For OER, ZnS@SnSe₂ composite required an overpotential of 234 mV to reach 10 mA cm⁻², a substantial improvement over ZnS (361 mV) and SnSe₂ (375 mV). Composite showcased a low Tafel slope of 48 mV dec^‑1 and an Rct of 1.5 Ω, comparable to commercial RuO₂ catalyst (44 mV dec^‑1, Rct = 2.2 Ω), further underscoring its superior oxygen evolution capabilities. In practical device configuration, ZnS@SnSe₂/NF electrode achieved a Tafel slope of 21.335 mV dec^‑1 for HER and 58.028 mV dec^‑1 for OER, demonstrating its bifunctional efficiency in a two-electrode system. The device exhibited exceptional long-term stability over 50 h of continuous operation, highlighting its potential for scalable and sustainable water splitting applications.