While perovskite light-emitting diodes typically made with high work function anodes and low work function cathodes have recently gained intense interests. Perovskite light-emitting devices with two high work function electrodes with interesting features are demonstrated here. Firstly, electroluminescence can be easily obtained from both forward and reverse biases. Secondly, the results of impedance spectroscopy indicate that the ionic conductivity in the iodide perovskite (CH3 NH3PbI3) is large with a value of approximate to 10(-8) S cm(-1). Thirdly, the shift of the emission spectrum in the mixed halide perovskite (CH3NH3PbI3-Br-x(x)) light-emitting devices indicates that I(-)ions are mobile in the perovskites. Fourthly, this work shows that the accumulated ions at the interfaces result in a large capacitance (approximate to 100 mu F cm(-2)). The above results conclusively prove that the organic-inorganic halide perovskites are solid electrolytes with mixed ionic and electronic conductivity and the light-emitting device is a light-emitting electrochemical cell. The work also suggests that the organic-inorganic halide perovskites are potential energy-storage materials, which may be applicable in the field of solid-state supercapacitors and batteries

Electrolysis in neutral pH solutions (e.g., wastewater and seawater) presents a transformative way for environmentally friendly, costeffective hydrogen production. However, one of the biggest challenges is the lack of active, robust hydrogen evolution reaction (HER) catalysts. Herein, we present a catalyst with dual-active sites of MoP 2 and MoP, which function synergistically to promote HER in neutral pH solutions. In our microbial electrolysis cell (MEC) test, which uses neutral pH wastewater as feedstock, this catalyst delivers an average HER current density of 157 A m cathode-surface-area −2 , higher than Pt catalyst (145 A m cathode-surface-area −2)with the same amount of catalyst loading, ∼5 times higher than the state-of-art Pt group metal-free catalysts in MECs. Our catalyst also outperforms Pt in natural seawater with ∼10% higher and more stable HER current density. The fundamental reason for the enhanced HER performance is identified to be the synergy between MoP 2 and MoP phases, with MoP 2 promoting H 2 O dissociation and MoP efficiently converting H ad into H 2 .

No abstract

No abstract