High-entropy sulfide nanoflowers with multi-atomic catalytic sites for efficient nitrate-to-ammonia conversion.

Electrocatalytic nitrate-to-ammonia conversion (NORR) offers a sustainable alternative to the energy-intensive Haber-Bosch process. High-entropy materials (HEMs), which exploit compositional diversity, lattice distortion, and d-band modulation, demonstrate remarkable electrocatalytic potential. However, they encounter significant synthesis challenges in achieving structural control and elemental homogeneity. Herein, a hollow spherical-flower NiCoFeV-S high-entropy sulfide is prepared a mild hydrothermal method. After optimizing the metal compositions and their respective proportions, the hollow spherical-flower NiCoFeV-S exhibits exceptional bifunctional performance. It requires only 267 mV of overpotential for the oxygen evolution reaction (OER) at 100 mA cm while simultaneously achieving remarkable performance in the NORR, with an ammonia yield of 16.6 mg h mg and a faradaic efficiency of 93.2%. Theoretical investigations identify three enhancement mechanisms: (1) hierarchical nanoarchitecture enabling maximized active site accessibility, (2) multi-metal synergy fine-tuning charge transfer dynamics, and (3) an upshifted d-band center synergistically accelerating water dissociation and hydrogenation kinetics. This work develops a simple synthesis strategy for HEMs, offering insights into their electronic structure modulation and holding significant promise for energy applications.