The highly sensitive photoelectric detection of hydrogen (H2) at room temperature (RT) is highly desired, but it is crucial to boost •O2- generation by improving charge transfer and favorable O2 adsorption. Herein, we construct a novel all-organic polydopamine/poly(heptazine imide) (PDA/PHI) nanosheet heterojunction through in situ polymerization for photoelectric H2 detection. The optimized one exhibits high sensitivity (an ultralow detection limit of 500 ppm and a high gas response of 42.8% for 5000 ppm H2), along with good linearity from 500 to 5000 ppm, under 405 nm irradiation at RT based on the dynamic detection process. Moreover, good repeatability in 40 cycles, long-term stability (over 210 days), and high selectivity are confirmed. The outstanding performance is attributed to the efficient Z-scheme charge transfer and the promoted O2 adsorption for facilitating the •O2- species generation. Interestingly, the in situ μs-transient absorption spectra quantitatively reveal that the electron transfer efficiency (ETE) to the adsorbed O2 of the PDA/PHI heterojunction is changed from 68.0% to 31.1% after introducing H2, while the change rate of ETE is more pronounced than that of PHI. This study demonstrates great potential of all-organic heterojunctions for RT photoelectric detection and provides deep insight into the •O2- species and gas sensing property.
Xu et al. (Wed,) studied this question.