Tianrong Zhan

The N ₂ -plasma technique converts NiFe-LDH surfaces into an ultrathin FeOOH film, promoting the formation and stability of NiOOH and blocking Cl ⁻ from active sites. The electrode shows outstanding OER performance in alkaline seawater electrolytes.

Efficient and durable oxygen evolution reaction (OER) catalysts are crucial for the generation of hydrogen via alkaline seawater electrolysis. Herein, an FeOOH/NiFe-LDH heterostructure with a built-in electric field (BEF) has been synthesized on Ni foam through a one-step cathodic electrodeposition. The formed BEF accelerates the OER kinetics by optimizing the interfacial electronic structure and enhancing the mass transfer and stabilizes the structure of the catalyst by Fe-O-Ni-O-Fe coupling bonds. In addition, the BEF and FeOOH mutually reduce the adsorption of Cl^- on the catalyst. Accordingly, FeOOH/NiFe-LDH demonstrates an outstanding OER catalytic performance in alkaline seawater electrolytes. In detail, FeOOH/NiFe-LDH displays small η₁₀₀ values of 265 and 278 mV in alkaline simulated and natural seawater, respectively, and achieves exceptional durability with smooth operation for ∼150 h at 250 mA cm^-2, albeit in a high-salt electrolyte (1 M KOH and 2.5 M NaCl). When FeOOH/NiFe-LDH is used as the anode of the AEM electrolyzer, the cell in alkaline simulated seawater delivers low voltages of 1.59 and 1.92 V at 100 and 500 mA cm^-2, respectively. The cell also shows excellent durability after operation over 110 h at 250 mA cm^-2 with an insignificant voltage increase of only 27 mV (∼0.25 mV h^-1). This work provides insight into the catalytic mechanism of the BEF-based heterostructure as anodic catalysts for alkaline seawater electrolysis.

Cheap and advanced electrocatalysts for the oxygen evolution reaction (OER) are vitally significant but challenging for seawater electrolysis. Herein, a glow discharge N₂ plasma is used to etch the [Fe(CN)₆]^4- group of the NiCoFe Prussian blue analogue (PBA) framework by highly reactive nitrogen radicals (the catalyst named N₂-NiCoFe-PBA). Abundant CN vacancies (V_CN) generated by this etching effectively suppress the Fe loss from N₂-NiCoFe-PBA, while the lack of V_CN results in the Fe leaching from the NiCoFe-PBA precursor during the anodic process. Consequently, N₂-NiCoFe-PBA and NiCoFe-PBA are transformed into real active phases of NiCoFeOOH and NiCoOOH during the OER process, respectively. Theoretical calculations display that NiCoFeOOH has superior adsorption capacity toward OH^- over Cl^- to NiCoOOH, which is beneficial to excellent OER activity and anticorrosion performance in alkaline seawaters. In alkaline simulated and natural seawater, N₂-NiCoFe-PBA exhibits much better OER performance with smaller η₁₀₀ (293 and 323 mV) than NiCoFe-PBA (405 and 434 mV). N₂-NiCoFe-PBA can run stably over 110 h in an alkaline high-salty electrolyte (1 M KOH + 2.0 M NaCl) at 250 mA cm^-2. This study provides a modification method without destroying the structure to develop efficient and stable OER catalysts for seawater electrolysis.

P-CoMoO ₃ /MoO ₂ exhibits excellent HER catalytic activities with MoO ₂ facilitating H–OH cleavage and CoMoO ₃ as the active site for hydrogen desorption.

The air plasma-induced defects and O-related groups are employed as anchoring sites for the directional electrochemical deposition of Ag nanoparticles (AgNPs) with even distribution and a narrow size range on carbon cloth (CC). The strategy of integrating the air plasma and AgNPs provides plentiful adsorption and catalytic sites, a large electroactive area, superhydrophilic interface, and a smooth charge and mass-transfer pathway. As a consequence, the fabricated self-supporting electrode of AgNPs@CC − P displays an excellent sensing performance toward rutin with a large linear concentration window (0.05 ~ 30 µM), a small LOD (4.2 nM, S/N = 3) and LOQ (32 nM, S/N = 10), as well as good stability and reproducibility. The fabricated sensor is successfully applied to the practical detection of rutin in tablets and beverages with good accuracy. The self-supporting sensor also shows potential for fabricating flexible and soft sensing devices for real-time monitoring. Graphical Abstract