Halide perovskite materials are excellent light harvesters that have generated enormous interest for photovoltaic technology and an increasing number of other optoelectronic applications.

Halide based lead perovskites are recently being explored as efficient light harvesters for optoelectronics devices. Here, some new insights on the self‐charging and energy‐storage of triple cation FA0.80MA0.15Cs0.05PbI2.55Br0.45 (FMCPIB) perovskites based devices with the application for self‐powered chemical sensing are presented. It is demonstrated that under light irradiation a self‐powered FMCPIB based device can detect particle per million (ppm) concentrations of nitrogen dioxide (NO2) with a swift response and recovery time of ≈17 and ≈126 s at room temperature, respectively. Most notably, the energy‐storage feature enables FMCPIB based devices like a photo‐capacitor, and then remain operational for another 1.7 h in darkness for the detection of NO2 without external power supply. Besides, the FMCPIB based devices can also be operated with a 1 V bias achieving a detection limit 0.2 ppm of NO2 at room temperature. Through analysis, it reveals that the high performance for NO2 can be ascribed to the special NO2‐amine interaction with the cations of FMCPIB and the storage capacitance might be due to the accumulation of charges at the TiO2/FMCPIB/carbon interfaces under light irradiation. These appealing features of FMCPIB perovskites based chemical sensors might find potential applications in monitoring of toxic gas emission and public space safety.

Humic acid (HA) is particularly important in iron-bearing mineral transformations and erosion at the water-mineral boundary zone of the Earth. In this study, three stages of the possible pathway by which HA causes mineral transformation from siderite to goethite are identified. Firstly, a Fe(II)-HA complex is formed by chelation, which accelerates the dissolution and oxidation of Fe(II) from the surface of siderite. As the Fe(II)-HA complex retains Fe atoms in close proximity of each other, ferrihydrite is formed by the agglomeration and crystallization. Finally, the ferrihydrite structurally rearranges upon attachment to the surface of goethite crystals and merges with its structure. The influence of low concentrations of HA (0-2 mg/L) on phosphate adsorption is found to be beneficial by the inducing of new mineral phases. We believe that these results provide a greater understanding of the impact of HA in the biogeochemical cycle of phosphate, mineral transformation.

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