Harvesting Green Hydrogen from The Deep Blue: Seawater-Compatible SnSe-P Decorated Graphene-CNTs Based Electrocatalyst Under Universal pH

Fabrication of cost-effective and robust metal-based electrocatalysts suitable for hydrogen evolution reactions (HER) within the entire pH range has drawn significant attention in harvesting renewable energy for the development of green automobile technology. Herein, a simple strategic approach has been adopted to design a 3D high-surface carbon-based heterostructure (Ni Foam-Graphene-CNTs) decorated with sharp-edged flakes of phosphorous-inserted tin selenide (SnSe-P) that helps in smoothing electrical conductivity, exposure of catalytic active sites (ECSA = 2353.5 cm²), modulating water dissociation kinetics, and cumulatively satisfying the peripheral chemical environment against HER kinetics at variable pH conditions. Thereby, it develops an outstanding performance in HER catalysis in terms of low overpotentials under variable conditions such as; 52 mV@ 10 mA cm^-2 in an acidic medium, 93 mV@10 mA cm^-2 in a basic medium, and 198 mV@10 mA cm^-2 in neutral medium. The linkage within the layers and the smooth interface with the carbon matrix make the catalyst versatile and exceptionally durable for at least 72 hours. Furthermore, the as-designed catalyst outperforms with a significantly low overpotential of 122 mV@10mA cm^-2 with long durability of at least 35 hours under alkaline seawater, which is approximately comparable to the performance achieved in recent findings. This is attributed to the controlled electronic distribution on the Sn site in SnSe-P and the low polarizability of bulky Sn atoms towards the precipitation of contaminants in seawater. Most importantly, the overall water electrolysis of the as-prepared catalyst (as a cathode) with RuO₂ (as an anode) generates a cell voltage of 1.56 V@10 mA cm^-2for a longer duration with a negligible potential loss in 1M KOH medium. The renewable strategy has been adopted using silicon solar cell (η = 10.66% ) to power up the electrolyzer demonstrates a stable photocurrent density of 6.40 mA cm^-2 for at least 36 hours with the solar-to-hydrogen (STH) conversion efficiency of 7.70% accompanied with the estimated STH of 5.65% in alkaline seawater medium. The mechanistic understanding <i>via</i> theoretical investigation reveals that the in-phase overlap between the px and py orbitals of Sn and P in NGC-SnSe-P (SnSe-3P/SWCNT) enables the s orbitals of H* and p orbitals of Sn to interact optimally closer to the Fermi level, which favors the adsorption H* intermediate of the HER process, also investigated experimentally by XANES and EXAFS analysis. This work may shed light on the development of versatile electrocatalysts for regulating the electrokinetics over wide operating conditions, typically for seawater electrolysis, adopting a renewable approach for the generation of green hydrogen towards a sustainable automobile sector.