Interface Engineering of Cobalt–Silver Molybdate Nanostructures for Bifunctional Water Splitting

The quest for competent electrode materials that sustainably catalyze the alkaline water oxidation process remains a continuous endeavor. In this context, integrating Ag into cobalt-based oxides can often enhance the water splitting performance. The current study delineates a facile wet chemical synthesis for the development of a cobalt–silver molybdate nanostructure (CoMoO 4 /Ag 2 MoO 4 (X% Ag)), with a focus on minimizing the cell potential for total water splitting (TWS). The optimized CoMoO 4 /Ag 2 MoO 4 (10% Ag) composite nanostructure on a redox-inactive carbon paper substrate demonstrates bifunctional activity with low overpotentials of 286 ± 7 mV and 67 ± 6 mV at a 10 mA/cm 2 current density toward alkaline oxygen evolution reaction (OER) and hydrogen evolution reaction (HER), respectively. Comprehensive physical characterizations verified that the integration of an adequate Ag 2 MoO 4 into the CoMoO 4 framework results in the formation of distinct Co–Ag heterojunctions, which trigger an increase in per-site activity, area-specific activity, and higher catalytic turnover frequency compared to pristine CoMoO 4 toward bifunctional water splitting. Also, CoMoO 4 /Ag 2 MoO 4 (10% Ag) exhibits a notably low Tafel slope (30 mV/dec) and reduced charge-transfer resistance (2.1 Ω), underscoring the role of Ag toward enhanced OER performance. Furthermore, the composite exhibits 90% Faradic efficiency (FE) and 94 h of extended stability, highlighting the importance of the Co–Ag molybdate nanostructure for prolonged catalysis in harsh alkaline conditions. Moreover, employed as both anode and cathode, the composite achieves 1.64 V cell potential at 10 mA/cm geo 2 current density in total water splitting (TWS) [CoMoO 4 /Ag 2 MoO 4 (10% Ag) (+) || CoMoO 4 /Ag 2 MoO 4 (10% Ag) (−)] with prolonged 110 h durability, featuring the suitability for practical applications.