Nitrogen-Terminated Diamond Films for Antiscaling Coatings

Abstract

Mineral scaling, particularly gypsum deposition, remains a costly and persistent problem in industrial systems, lowering efficiency, raising energy demands, and accelerating equipment degradation. Conventional chemical and mechanical mitigation methods are temporary and often introduce secondary environmental or operational concerns, underscoring the need for intrinsically scale-resistant materials. Herein, we report a systematic investigation of polycrystalline diamond (PCD) films with varied surface terminations (oxygen, hydrogen, fluorine, or nitrogen) for their resistance to CaSO₄ scaling. Nitrogen-terminated PCD (N-PCD) exhibits an order-of-magnitude reduction in Ca²⁺ accumulation compared with other terminations. Scanning electron microscopy (SEM) reveals that N-PCD supports only sparse, dendritic gypsum crystallites, in contrast to the dense, continuous scale layers observed on other surfaces. Consistently, adhesion force measurements confirm extremely low adhesion between the CaSO₄ crystal and N-PCD. Molecular dynamics and density functional theory simulations show that a strongly bound, ordered water layer forms on N-PCD, creating an energetic barrier that repels CaSO₄ ions and suppresses heterogeneous nucleation. Further enhancement is achieved by bulk nitrogen doping, which smooths the surface morphology and suppresses scale formation by up to 6-fold. Finally, applying nitrogen functionalization to commercial boron-doped diamond (BDD) electrodes yields seven times lower scale loading without compromising electrochemical performance. This combined experimental-theoretical study establishes nitrogen-functionalized diamond as a robust, durable platform for antiscaling coatings, with potential applications across water treatment, energy production, and other scaling-prone industries.