Electrochemical enhanced betavoltaic cells based on ZrO2@TiO2 nanorod arrays with type-I band alignment

Abstract

Direct energy conversion from beta radiation to electricity using betavoltaic effect is a promising energy conversion technology for a long-time and highly efficient power supply. This work presents an electrochemical betavoltaic cell (EBC), consisting of a beta-anode with TiO2 nanorod arrays (TNRAs) modified with ZrO2 nanoparticles, a polyiodide (I−/I3−) electrolyte, and a 63Ni/Ni counter electrode. Free-standing TNRAs structures were fabricated using hydrothermal method and post-annealed in Ar atmosphere to enable a rutile TiO2 material with excellent electrochemical performance. Monte Carlo (MC) method was used to determine the optimum length (∼2.5 μm) of the TiO2 nanorods. Investigation on ultraviolet photoelectrochemical performance of EBCs was used to evaluate and optimize the content of ZrO2 (thickness of ∼10 nm) modified on the TNRAs. The EBCs demonstrated an energy conversion efficiency of 9.27% with an open-circuit voltage of 0.276 V and short-circuit current density of 1.041 μA·cm−2 when using a 10 mCi 63Ni source. The enhanced performance can be ascribed to the three-dimensional ZrO2/TiO2 heterojunction with a large specific area in favor of the interface carrier transfer as well as the suppression of carrier recombination through the type-I band barrier, effectively promoting the electrochemical redox reaction.