A bio-inspired strategy for enhanced hydrogen evolution: carbonate ions as hole vehicles to promote carrier separation

Abstract

Natural photosynthesis involves a subtle electron transfer mechanism in which freely-moving electron transfer intermediates (plastoquinone and plastocyanin) are capable of effectively separating the photo-generated carriers, and therefore, it has high quantum efficiency. Inspired by this mechanism, in this study, carbonate (CO₃²⁻) ions were employed as hole vehicles to promote photo-generated carrier separation, and greatly improved the photocatalytic hydrogen evolution activity of K₄Nb₆O₁₇ nanosheets. The hydrogen evolution rate at the optimal concentration of CO₃²⁻ ions reached 2018 μmol h⁻¹ g⁻¹, which was 16.3 times that of the blank sample (124 μmol h⁻¹ g⁻¹). This marked enhancement was based on the transfer of holes from the photocatalyst to the sacrificial reagent (methanol) via CO₃²⁻ ions; this process is faster than direct hole transfer between the photocatalyst and sacrificial reagent. This bio-inspired strategy provides a facile and cost-effective approach to improve the solar-to-fuel conversion efficiency of photocatalysts.