Innovative multifunctional hybrid photoelectrode design based on a ternary heterojunction with super-enhanced efficiency for artificial photosynthesis

Abstract

Electrochemical cells for direct conversion of solar energy to electricity (or hydrogen) are one of the most sustainable solutions to meet the increasing worldwide energy demands. In this report, a novel and highly-efficient ternary heterojunction-structured Bi₄O₇/Bi_3.33(VO₄)₂O₂/Bi₄₆V₈O₈₉ photoelectrode is presented. It is demonstrated that the combination of an inversion layer, induced by holes (or electrons) at the interface of the semiconducting Bi_3.33(VO₄)₂O₂ and Bi₄₆V₈O₈₉ components, and the rectifying contact between the Bi₄O₇ and Bi_3.33(VO₄)₂O₂ phases acting afterward as a conventional p–n junction, creates an adjustable virtual p–n–p or n–p–n junction due to self-polarization in the ion-conducting Bi₄₆V₈O₈₉ constituent. This design approach led to anodic and cathodic photocurrent densities of + 38.41 mA cm^–2 (+ 0.76 V_RHE) and– 2.48 mA cm^–2 (0 V_RHE), respectively. Accordingly, first, this heterojunction can be used either as photoanode or as photocathode with great performance for artificial photosynthesis, noting, second, that the anodic response reveals exceptionally high: more than 300% superior to excellent values previously reported in the literature.