Investigation of ultrashort (< 1 min) calcination processes for conversion of Pt–SnOx from mixture of chloroplatinic acid and tin(II) chloride

Abstract

We investigate the ultrashort (< 1 min) calcination process for Pt–SnOx catalysts converted from a mixture solution of chloroplatinic acid and tin(II) chloride in air. An electric furnace is used to test the ultrashort calcination of Pt–SnOx catalysts used as counter electrodes (CEs) of DSSCs. By using a conventional electric furnace instead of an atmospheric pressure plasma jet (Metals 8:690, 2018), the effect of reactive plasma species can be ruled out, and only the bare thermal effect is considered in this study. Scanning electron microscopy reveals that Pt–SnOx nanoparticles are well-distributed on the substrates. X-ray photoelectron spectroscopy indicates the conversion of a large amount of metallic Pt and oxidized Sn. No metallic Pt is observed with 5-s calcination; however, ~ 74% Pt is converted into metallic Pt with 15-s calcination. Further increasing the calcination time does not increase the conversion rate of metallic Pt. By contrast, metallic Sn shows its maximum conversion rate of ~ 18% with 30-s calcination. Further increasing the calcination time to 30 min reduces the metallic Sn content to ~ 6%, possibly owing to Sn re-oxidation. When applying Pt–SnOx catalysts to CEs of DSSCs, the efficiency greatly increases as the calcination time increases from 15 to 30 s. The efficiency remains relatively unchanged for calcination time of 60 s to 30 min. The efficiencies of DSSCs with a Pt–SnOx CE calcined at longer processing times (≥ 60 s) are comparable to those of DSSCs with conventional Pt CEs. The left-hand-side image shows the Pt–SnOx nanoparticulate compounds. The right-hand-side figure shows the J–V curves.