Enhanced photocatalytic hydrogen evolution from cation modified single perovskite niobates in the absence of noble metal cocatalysts

Abstract

Meeting the growing demand for robust, earth-abundant and noble-metal-free photocatalysts for practical hydrogen-evolution reaction systems is crucial. Herein, cation modified perovskite niobates, Na_0.5Sr_0.5M_0.25Nb_0.75O₃ (M = Cr, Mn, Fe, Co), are synthesized using a simple heterovalent coupled substitution strategy via solid-state reactions. The Cr compound as a single semiconductor system exhibits a photocatalytic hydrogen evolution rate of 188 μmol h⁻¹ g⁻¹, which significantly surpasses the performance of many contemporary catalysts that rely on the use of noble metal cocatalysts. Apparent quantum efficiencies (AQEs) of Cr, Mn, Fe and Co containing compounds are 2.24, 0.55, 0.65 and 0.74%, respectively. The photophysical properties like tuned band gap, suitable energy level positioning, charge carrier density, photostability of the materials and charge transfer resistance that are responsible for efficient spatial charge separation and charge transfer dynamics impacting the hydrogen evolution are investigated. This paper discusses the role of cation modification and its effects on the photophysical properties and hydrogen evolution activity of the perovskite niobates under noble-metal free conditions. These nonprecious noble-metal-free perovskite niobates furnish a new perspective for the future design of photocatalysts for efficient photocatalytic hydrogen evolution.