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 (CoMoO4/Ag2MoO4(X% Ag)), with a focus on minimizing the cell potential for total water splitting (TWS). The optimized CoMoO4/Ag2MoO4 (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/cm2 current density toward alkaline oxygen evolution reaction (OER) and hydrogen evolution reaction (HER), respectively. Comprehensive physical characterizations verified that the integration of an adequate Ag2MoO4 into the CoMoO4 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 CoMoO4 toward bifunctional water splitting. Also, CoMoO4/Ag2MoO4 (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/cmgeo2 current density in total water splitting (TWS) [CoMoO4/Ag2MoO4 (10% Ag) (+) || CoMoO4/Ag2MoO4 (10% Ag) (−)] with prolonged 110 h durability, featuring the suitability for practical applications.