ZnO-decorated nanoporous Ag with Pt-like Tafel slopes as HER catalysts in alkaline electrolytes manipulated by cyclic square-wave potential sweeping dealloying

Three cyclic square-wave potential sweeping dealloying (CSW) modes have been developed to manipulate the dealloying depth and nanoporosity of dual-phase Ag_35.5Zn_64.5 precursors with the ultimate aim of enhancing the performance of hydrogen evolution reactions. The evolution of the bimodal nanoporous structures is governed by two factors: the initial microstructure of the dual-phase Ag_35.5Zn_64.5 precursors and the cyclic frequency of the CSW dealloying. It is found that the pore sizes can be refined below 20 nm with an increase in the cyclic frequency of CSW as high as 21600 through the restricted diffusion in the single cycle with short cyclic time. Among the nanoporous Ag obtained through the modes of potentiostatic dealloying and CSW with varying cyclic frequencies (f: 1, 216 and 21600), the composites nanoarchitecture at CSW with a cyclic frequency of 21600 exhibits the superior HER catalytic performance in comparison to nanoporous Ag in the potentiostatic dealloying and bulk Ag plate. The nanoporous Ag nanoarchitectures decorated with ZnO nanograins with an average particle size of approximately 6.2 nm, possess an overpotential of 290 mV at 10 mA cm⁻² and a Pt-like low Tafel slope of 39.4 mV dec⁻¹. These properties are attributed to the rapid sweeping of square-wave potential in CSW with a frequency of 21600. The boosted catalytic performance of hydrogen evolution reactions, governed by the Volmer-Heyrovsky mechanism, is attributed to the enrichment of Ag (111) facets and the enlargement of the surface area of ultrafine nanoporosity of ZnO-decorated Ag porous nanoarchitectures.