Sulfur‐Vacancy Anchoring Suppresses Dynamic Surface Reconstruction in Ni‐Doped ZnS Nanospheres to Trigger the Lattice Oxygen Mechanism

Why It Matters

By stabilizing the catalyst surface and enabling lattice‑oxygen participation, the vacancy‑engineered material dramatically lowers the energy cost of water splitting, accelerating commercial hydrogen production. The findings provide a blueprint for designing defect‑rich sulfide catalysts across renewable‑energy technologies.

Key Takeaways

• Sulfur vacancies reduce metal dissolution during OER
• Vacancies suppress surface reconstruction, forming Ni‑Zn(OH)2/ZnS heterojunction
• Weakened Zn‑O bonds enable lattice oxygen mechanism
• Catalyst achieves 180 mV overpotential at 10 mA cm⁻²
• Tafel slope recorded at 48.7 mV dec⁻¹

Pulse Analysis

The oxygen evolution reaction remains a bottleneck for scalable electro‑water splitting, largely because catalyst surfaces undergo rapid reconstruction under high anodic potentials. Traditional transition‑metal oxides often dissolve or restructure, eroding activity and durability. Recent research highlights defect engineering as a strategic lever, where intentionally introduced vacancies can steer surface chemistry away from detrimental pathways. In the case of nickel‑doped zinc sulfide, sulfur vacancies act as anchors that curb metal leaching and preserve the nanosphere’s integrity, setting the stage for more reliable OER performance.

When the vacancy‑rich ZnS nanospheres encounter alkaline electrolyte, they spontaneously form a Ni‑Zn(OH)2/ZnS heterojunction at the surface. This interface weakens the Zn‑O bond, creating non‑bonding electronic states that facilitate the lattice oxygen mechanism—a pathway where lattice oxygen directly participates in O₂ evolution rather than relying solely on adsorbed water molecules. Compared with the conventional adsorbate evolution mechanism, the lattice oxygen route can lower the kinetic barrier, which is reflected in the reported 180 mV overpotential at 10 mA cm⁻² and a modest 48.7 mV dec⁻¹ Tafel slope. These metrics place the material among the most efficient non‑precious‑metal OER catalysts in 1 M KOH.

The broader implication is clear: controlling defect populations offers a scalable route to high‑performance, low‑cost water‑splitting catalysts. By mitigating dissolution and harnessing lattice oxygen, manufacturers can design electrolyzers that operate at reduced voltage, cutting electricity consumption and capital costs. Future work will likely explore vacancy‑driven heterojunctions in other sulfide and phosphide systems, integrating computational screening with in‑situ spectroscopy to accelerate discovery. As the renewable energy sector seeks greener hydrogen, such defect‑centric strategies could become a cornerstone of next‑generation electrochemical technologies.