In situ generated sulfate-facilitated efficient nitrate electrosynthesis on 2D PdS2 with unique imitating growth feature

Electrocatalytic nitrogen oxidation (NOR)—the green alternative to the century-old, energy-guzzling Ostwald process—has long been stifled by the formidable 941 kJ mol⁻¹ N≡N bond and the relentless competition from oxygen evolution. In a breakthrough review published in Nano-Micro Letters, researchers from Liaoning University and RMIT University, led by Professors Hui Mao and Tianyi Ma, demonstrate how interface-engineered 2D PdS₂ nanoplates decisively overcome both hurdles, delivering record nitrate yields with unprecedented stability.

Why PdS₂ Now Matters

• Imitating-Growth Morphology: PdS₂ “copies” the topography of its 2D substrate. Anchored on PVEIB/PPy/GO, it crystallizes into ultra-thin, defect-rich nanoplates (~25 nm) that expose abundant sulfur vacancies—prime sites for catalysis.
• Self-Generating Sulfate: Those same vacancies spontaneously oxidize to SO₄^2- during synthesis or at high anodic potentials. This in-situ sulfate slashes the activation energy of the rate-limiting N₂→*NNOH step from 2.95 eV to 1.92 eV, a 35 % cut that outperforms state-of-the-art Ru-doped oxides.
• Triple Synergy: GO supplies a vast surface, PPy accelerates electron transport, and PVEIB imidazolium groups sterically confine growth—yielding a composite with 93.9 µg h^-1 mg^-1 nitrate productivity and 7.36 % Faradaic efficiency at only 2.05 V vs RHE.

Enduring Performance Under Harsh Conditions

• 30-hour Continuous Electrolysis: No decay in current or crystal structure, verified by post-mortem TEM and synchrotron HERFD-XANES.
• Six-Cycle Stress Test: >95 % activity retained, versus >80 % loss for bare PdS₂.
• 100 % Selectivity: Ion chromatography detects only NO₃⁻—zero NO₂⁻, NH₃, or gaseous by-products.

Mechanistic Insight: Sulfate as the Silent Co-Catalyst

Real-time ATR-SEIRAS captures the ascent of bridging bidentate nitrate peaks (1245 & 1646 cm^-1) that mirror anodic current, confirming an associative distal pathway. DFT charge-density maps reveal that SO₄^2- modulates electron donation from Pd to *NNOH, weakening the N–N bond and accelerating turnover. Electrochemical impedance collapses from 2.7 kΩ to 310 Ω, underscoring faster interfacial charge transfer.

Future Outlook

The imitating-growth protocol is substrate-agnostic—ready to be ported to MXene, g-C₃N₄, or other novel TMDs. Scalable hydrothermal synthesis (>1 g batches) and binder-free electrode casting already deliver >200 mA cm^-2 in a flow-cell prototype. Coupled with renewable electricity, this sulfate-coupled platform could decentralize nitrate production, cutting CO₂ emissions from the Ostwald process by more than 70 %. Stay tuned as the Mao and Ma team advances from coin cells to containerized NOR units, turning air and water into fertilizer—one volt at a time.