Oxygen vacancy-rich Ni(OH)2-ZnWO4 composites as an effective electrocatalyst for water splitting

A major ongoing challenge is the growth of stable and effective electrocatalysts for generating hydrogen through water splitting. In this research work, zinc tungstate (ZnW), nickel hydroxide (Ni(OH)2), and their nanocomposites (Ni(OH)2-ZnW) with different ratios (1:5 and 2:5) were synthesized using the hydrothermal method and utilized as electrocatalyst for the process of overall water splitting. SEM images revealed that the rod and plate-like shapes of ZnW and Ni(OH)2 merged in their nanocomposites. The Ni(OH)2-ZnW (1:5) nanocomposite exhibited higher electrochemical surface area and electrocatalytic efficiency, particularly for hydrogen production than pristine materials and Ni(OH)2-ZnW (2:5) composite. The onset overpotentials for Ni(OH)2-ZnW (1:5) were found to be -466 mV for HER and 200 mV for OER in 2 M KOH with Tafel slopes of 287 mV dec- 1 and 171 mV dec- 1 respectively. The catalyst maintains stable activity with no significant degradation for 2 h of HER reaction. The XPS probing witnessed that Ni(OH)2-ZnW (1:5) was an oxygen valency-rich material which caused an improved response in water-splitting reactions. The findings suggested that the nanocomposite with 1:5 concentration is the best choice for bifunctional electrocatalysts for future hydrogen production reactions.