Laser-Ironing Induced Capping Layer on Co-ZIF-L Promoting In Situ Surface Modification to High-Spin Oxide–Carbon Hybrids on the “Real Catalyst” for High OER Activity and Stability

The development of high-performance, stable electrocatalysts is vital for advancing renewable energy technologies, particularly for the oxygen evolution reaction (OER) in water splitting, a key process for sustainable hydrogen production. Metal-Organic Frameworks (MOFs), with their high surface areas, tunable porosity, and versatile structural design, are promising candidates for catalytic applications. However, MOFs often oxidize and degrade during OER, leading to reduced catalytic activity and stability. Although some traditional treatments, such as high-temperature furnace processes, are used to convert MOFs into other compounds, they still face stability challenges during OER.<br/><br/>This study introduces a novel laser-ironing (LI) technique that forms an in-situ laser-ironing capping layer (LICL) on Co-ZIF-L, one type of MOF with a unique flake structure, preserving structural integrity and significantly enhancing OER performance. Using a low-power laser, the LI method converts the surface of Co-ZIF-L grown on carbon cloth into a LICL composed of higher crystallinity graphitic carbon and Co nanocrystals. This process retains the leaf-like morphology and promotes the formation of OER-active Co₃O₄ nanoclusters during OER. In contrast, Co-ZIF-Ls treated with conventional thermal methods collapse and transform into less active CoOOH.<br/><br/>Density functional theory (DFT) calculations highlight the role of high spin (HS) states of Co ions and a narrowed band gap in Co₃O₄ nanoclusters, which enhance OER activity by facilitating spin-selected electron transport, reducing the energy barrier, and enabling a spontaneous O₂-releasing step, the potential-determining step in CoOOH. The resulting LICL stabilizes the catalyst structure, delivering considerable performance metrics: a low overpotential of 290.16 mV, a Tafel slope of 58.95 mV dec⁻¹, and remarkable stability with a 1.56% increase in current density after 20 hours of high-voltage OER. The high crystallinity carbon in LICL reduces electrical resistance and affects the formation of Co₃O₄ nanoclusters through confinement, resulting in optimized OER kinetics and thermodynamics.<br/><br/>This novel LI method offers a controllable, efficient, and low-cost approach for fabricating high-performance electrocatalysts, addressing the critical challenge of maintaining stability and performance during dynamic electrochemical reactions. Beyond OER, the implications of this research extend to sensors, batteries, and wearable electronic devices, providing a versatile method for surface modification and catalyst design. By combining ultra-high temperatures with an ultra-fast process, LI ensures precise control over surface microstructure, preventing aggregation and preserving the unique morphology of MOFs. This technique addresses significant issues associated with traditional thermal treatments, such as high energy consumption, lengthy processing times, and structural degradation.<br/><br/>Our findings demonstrate that LI-induced LICL provides a stable, high-performance catalyst that undergoes a pseudomorphic transformation during OER, forming CoOOH arrays with retained morphology and enhanced surface area. This transformation, driven by HS state Co₃O₄ nanoclusters, significantly lowers the energy barrier and improves overall catalytic activity.<br/><br/>In conclusion, the LI technique represents a promising advancement in electrocatalysis, offering a novel pathway for designing stable and efficient catalysts. This approach addresses fundamental real-world challenges related to energy conversion efficiency and catalyst durability, making hopeful strides toward sustainable and scalable hydrogen production. Our work contributes to the broader goal of renewable energy development and introduces a transformative strategy for high-precision surface microstructure control.