Theoretical insight into single Rh atoms anchored on N-doped γ-graphyne as an excellent bifunctional electrocatalyst for the OER and ORR: electronic regulation of graphitic nitrogen.

Reducing the overpotential and increasing the reaction rate, which are respectively determined by the thermodynamics and kinetics of electrocatalysis, are the keys to obtaining high-performance bifunctional electrocatalysts for the OER/ORR. Herein, six late-transition metals (Ru, Rh, Pd, Os, Ir, and Pt) anchored on γ-GY and graphitic N doped γ-GY substrates are screened as electrocatalysts for the OER and ORR via density functional theory, and the effects of electronic regulation due to the presence of graphitic N on the thermodynamics and kinetics of electrocatalysis are investigated in detail. Among the six γ-GY@TM candidates, only γ-GY@Rh exhibits excellent OER activity, with an overpotential of 0.42 V. Furthermore, graphitic N doped graN-γ-GY@Rh shows outstanding bifunctional electrocatalytic activity, with overpotentials of 0.27 V for the OER and 0.33 V for the ORR, which are remarkably superior to the values of 0.43 V for RuO2 and 0.45 V for noble-metal Pt electrocatalysts. The present results present some of the lowest overpotentials for OER/ORR electrocatalysts given by theoretical studies to date. From a kinetics point of view, N-doping also remarkably reduces the activation energy barriers of the catalytic rate-limiting steps of the OER and ORR, accelerating the reaction processes and significantly improving the conductivity. Our work provides a theoretical strategy for designing high-efficiency bifunctional OER/ORR electrocatalysts based on γ-GY materials.

Blue-emitting NH4+-doped MAPbBr3 perovskite quantum dots with near unity quantum yield and super stability.

Novel NH4+-doped MA1-x(NH4)xPbBr3 perovskite quantum dots were synthesized at room temperature. The introduction of NH4+ results in larger lattice formation energy and better crystallinity of MA1-x(NH4)xPbBr3, which greatly reduces the defect density and inhibits non-radiative recombinations, and thus helps in achieving excellent stability and near unity blue-emitting photoluminescence quantum yields.