Construction of a novel BaZr0.1Ce0.7Y0.2O3-δ-SnO2 heterojunction composite electrolyte for advanced semiconductor ion fuel cells operating at lower temperature down to 350

[Display omitted] •We design a novel BZCY-SnO2 composite electrolyte with proton dominated mixed ion conduction.•The synergistic effect of BZCY-SnO2 composite further lower the melting point temperature of Li2CO3/LiOH complex.•The built-in electric field from BZCY-SnO2 heterojunction effectively promote the ions (H+and O2–) conduction.•The single cell with 7BZCY-3SnO2 electrolyte still achieve an MPD of 92 mW/cm2 at low temperature of 350 °C. One of the challenges facing in semiconductor ion fuel cells (SIFCs) is overcoming the limitation of low temperature (below 400 °C). Proton conductor material, holding low transport activation energy to deliver protons, have become a significant alternative candidate for seeking for high performance electrolyte. Herein, we designed a proton dominated mixed ion (H+/O2−) conduction BaZr0.1Ce0.7Y0.2O3-δ-SnO2 (BZCY-SnO2) composite material using proton-conducting BZCY as the electrolyte of SIFCs for the first time. The composite not only fully utilizes the properties of proton-conducting BZCY and wide bandgap SnO2, but also takes advantage of the heterojunction characteristics formed between BZCY and SnO2. Furthermore, the built-in electric field in BZCY-SnO2 heterojunction promotes the ion (H+ and O2–) conduction while suppresses electronic (e-) conduction, thereby improving the overall performance of the single cell. As a result, the single cell with 7BZCY-3SnO2 composite electrolyte achieved a peak power density of 1102 mW/cm2 and remarkable ionic conductivity of 0.155 S·cm−1 at 550 °C. Specially, the synergistic effect of the BZCY-SnO2 composite electrolyte can further lower the melting point temperature of Li2CO3/LiOH complex in the electrolyte. This results in a further reduction in the operating temperature of the single cell. And then the device can still obtain a power output of 92 mW/cm2 at 350 °C. The innovative design can effectively overcome the common bottleneck phenomenon of cell operation temperature at temperature below 400 °C. This strategy opens up new avenues for the electrolyte development and application of SIFCs.