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

Electrocatalytic nitrate-to-ammonia conversion (NO₃RR) 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 via 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^-2 while simultaneously achieving remarkable performance in the NO₃RR, with an ammonia yield of 16.6 mg h^-1 mg_cat. ^-1 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.