A series of TiO 2 /nitrogen (N) doped reduced graphene oxide (TiO 2 /NrGO) nanocomposites with varying concentration and bonding configurations of nitrogen were synthesized by a one-step urea-assisted hydrothermal method, and applied to photoreduction of CO 2 with H 2 O vapor in the gas-phase under the irradiation of a Xe lamp. The effect of the N dopant (doping quantity and bonding configuration) on the catalytic performance of TiO 2 /NrGO was examined. In particular, TiO 2 /NrGO-300, with a 300:1 mass ratio of urea/GO in precursor solution, had the highest CO production yield (356.5 μmole g-1), manifesting a significant 4.4 and 2.2-fold enhancements of CO yield over pure TiO 2 and TiO 2 /rGO, respectively. More significantly, TiO 2 /NrGO showed excellent catalytic stability during the prolonged reaction, while catalytic deactivation was observed for both pristine TiO 2 and TiO 2 /rGO after a few hours. The promoting effects of N dopants on the structure and activity of TiO 2 /NrGO were investigated. It was demonstrated that NrGO with an appropriate N quantity and N-bonding configuration acted as a dual-functional promoter, simultaneously enhancing CO 2 adsorption on the catalyst surface and facilitating electron-hole separation, while eventually boosted the photocatalytic performance. Experimental results in this work provide a better understanding of the critical roles of N dopants in the synthesized composites and also inspire the ongoing interest in better design of other N-doped graphene based materials for photoreduction of CO 2 .

Solar cells made up of lead-halide perovskites have shown a remarkable increase in power conversion efficiency; however, they are plagued with instability issues that, combined with the toxicity of lead, have led to a search for new semiconductors made up of heavy and nontoxic metals such as bismuth. Here, we report on a new, inorganic, double perovskite oxide semiconductor: KBaTeBiO 6 , which has an experimental indirect band gap of 1.88 eV and shows excellent stability. We combined data analytics and high throughput density functional theory calculations to search through thousands of hypothetical inorganic double perovskite oxides containing bismuth and predict KBaTeBiO 6 as a potential photovoltaic material, which was subsequently synthesized using a wet-chemistry route. The calculated effective mass of the charge carriers for KBaTeBiO 6 is comparable to the best performing Bi-halide double perovskites. Our work demonstrates the untapped potential of inorganic Bi-based double perovskite oxidesthat offer the ability to change both the cation combination and their stoichiometry to achieve desired electronic propertiesas exciting, benign, and stable alternatives to lead-halide perovskites for various semiconducting applications.

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