Surface sulfurization of structure-modulated V₂O₅ via Cd-doping (CdVOx@S) enables boosted water-splitting in an alkaline medium

Water splitting into hydrogen and oxygen is highly desirable for fuel production, but electrocatalysis poses challenges for commercial applications due to overpotential, high current density, and a lack of long-term stability. To overcome this difficulty, it is essential to design stable and highly efficient catalysts. Transition metal-based bimetallic oxides have emerged as promising options for OER and HER in alkaline media. However, the utility of bimetallic oxide has been limited by the lower formation of active sites. Therefore, this research explores the hetero-anionic structure of the sulfide anion with a bimetallic oxide (CdVOx@S) through hydrothermal and sulfurization treatments. Hybridizing with sulfide ions revealed the collaborative effect of hetero-interfaces via modulated electronic reconstruction. The TEM investigation revealed the core-shell morphology of CdVOx@S, which also meets interfacial defects to optimize the adsorption of oxyhydroxide and desorption of hydrogen species. The CdVOx@S is used by growing on an SS substrate, as this achieved a low overpotential of 220 and 176 mV to deliver 10 mA cm⁻² toward OER and HER. Benefiting from a strong coordination environment, CdVOx@S highlighted a large surface area of 2094 cm², as confirmed by ECSA. Compared to CdVOx, the composite exhibited the lowest Tafel slopes (67 and 51 mV dec⁻¹ for OER and HER) as it had the lowest charge-transfer resistance, as evaluated from EIS. These results demonstrate the advantage of the hetero-anionic strategy for the core-shell design as exposed active sites open the channels for rapid S→CdVOx electron transfer and conductivity towards gas product emission. Moreover, the superior stability of CdVOx@S offers favorable evidence for its potential in realistic energy conversion applications.