Selective etching of Sm_0.5Sr_0.5CoO_3-δ ceramic for solar evaporator with photocatalytic purification

The ultimate goal of solar driven water evaporation is to obtain clean water without volatile organic pollutants. Current strategies mainly depend on the integration of the photo-thermal conversion and photocatalytic degradation by a multi-step composite technique. In this work, a facile nitric acid etching method was adopted to prepare the photothermal-catalytic bifunctional material (Sm_0.5Sr_0.5CoO_3-δ-Co₃O₄). The effect of the acid-etching treatment on the Sm_0.5Sr_0.5CoO_3-δ surface evolution was investigated. The Sm_0.5Sr_0.5CoO_3-δ (SSC5) surface was selectively reconstructed, and the catalytic active B-site cobalt cation was randomly exposed after the acid-etching treatment. The unique structure of SSC5-Co₃O₄ was beneficial to the electrons transport between Co₃O₄ and SSC5, as well as the solar absorbance. The nitric acid-etched SSC5 honeycomb ceramic exhibited a solar absorption of 80%, resulting in an evaporation rate of 7.25 kg·m⁻²·h⁻¹ under a simulated sunlight of 1000 mW·cm⁻². Besides, the etched SSC5 exhibited the ability for pollutant (Congo red) degradation. The as-prepared acid-etched SSC5 honeycomb ceramic could integrate the solar evaporation with pollutant degradation, which has a promising application in the pure water production.