Anodic TiO2 nanotube arrays prepared by electrochemical anodization were used to fabricate ultraviolet (UV) photodetectors. The devices annealed at 450 °C exhibit the highest UV-sensitive photoconductance due to the pure anatase phase of the TiO2. The large surface area and one-dimensional nanostructure of the TiO2 nanotubes lead to great photosensitivity (more than 4 orders of magnitude) and fast response with rise time and decay time of 0.5 and 0.7 s, respectively. High responsivity of 13 A/W is found under 1.06 mW/cm2 UV (λ = 312 nm) illumination at 2.5 V bias, which is much higher than those of commercial UV photodetectors. The high responsivity mainly comes from the internal gain induced by the desorption of oxygen from the nanotube surfaces and the reduction of the Schottky barrier at TiO2/Ag contact under UV illumination. The devices are promising for large-area UV photodetctor applications.

The extensive deployment of the electrocatalytic CO 2 reduction reaction (CO 2 RR) is presently limited by the utilization of alkaline/neutral electrolytes in which carbonate formation severely reduces the carbon efficiency and electrolysis stability. By contrast, the CO 2 RR in a strong acid electrolyte can overcome these shortcomings, yet the hydrogen evolution reaction (HER) greatly outcompetes the CO 2 RR in acidic media. Herein, CO 2 reduction to HCOOH, a significant chemical intermediate in many industrial processes, was realized in strong acid (pH ≤ 1) through introducing K + cations into the electrolyte. The K + -assisted acidic CO 2 RR accordingly manufactured HCOOH with a high Faradaic efficiency of 92.2% @−1.23 V RHE and a commercially relevant current density of −237.1 mA cm −2 . More importantly, a high single-pass carbon efficiency of 27.4% for HCOOH production was demonstrated in acid, which exceeded the value obtained in the alkaline CO 2 RR. Further mechanistic studies demonstrated that K + can engineer the local microenvironment over the Bi catalyst surface by reducing the proton coverage to suppress the competing HER and creating local interaction to stabilize the *OCOH intermediate, which ultimately promotes high-efficiency CO 2 conversion to HCOOH in strong acidic media.

Injecting an electron by scanning tunneling microscope into a molecule physisorbed at a surface can induce dissociative reaction of one adsorbate bond. Here we show experimentally that a single low-energy electron incident on ortho-diiodobenzene physisorbed on Cu(110) preferentially induces reaction of both of the C-I bonds in the adsorbate, with an order-of-magnitude greater efficiency than for comparable cases of single bond breaking. A two-electronic-state model was used to follow the dynamics, first on an anionic potential-energy surface (pes*) and subsequently on the ground state pes. The model led to the conclusion that the two-bond reaction was due to the delocalization of added charge between adjacent halogen-atoms of ortho-diiodobenzene through overlapping antibonding orbitals, in contrast to the cases of para-dihalobenzenes, studied earlier, for which electron-induced reaction severed exclusively a single carbon-halogen bond. The finding that charge delocalization within a single molecule can readily cause concerted two-bond breaking suggests the more general possibility of intra- and also intermolecular charge delocalization resulting in multisite reaction. Intermolecular charge delocalization has recently been proposed by this laboratory to account for reaction in physisorbed molecular chains (Ning, Z.; Polanyi, J. C. Angew. Chem., Int. Ed. 2013, 52, 320-324).

Although Fenton or Fenton-like reactions have been widely used in the environment, biology,life science,and other fields,t he sharp decrease in their activity under macroneutral conditions is still al arge problem. This study reports aM oS 2 cocatalytic heterogeneous Fenton (CoFe 2 O 4 /MoS 2 )s ystem capable of sustainably degrading organic pollutants,s uch as phenol, in am acroneutral buffer solution. An acidic microenvironment in the slipping plane of CoFe 2 O 4 is successfully constructed by chemically bonding with MoS 2 .T his microenvironment is not affected by the surrounding pH, which ensures the stable circulation of Fe 3+ /Fe 2+ on the surface of CoFe 2 O 4 /MoS 2 under neutral or even alkaline conditions. Additionally,C oFe 2 O 4 /MoS 2 always exposes "fresh" active sites for the decomposition of H 2 O 2 and the generation of 1 O 2 , effectively inhibiting the production of iron sludge and enhancing the remediation of organic pollutants,even in actual wastewater.T his work not only experimentally verifies the existence of an acidic microenvironment on the surface of heterogeneous catalysts for the first time,but also eliminates the pH limitation of the Fenton reaction for pollutant remediation, therebye xpanding the applicability of Fenton technology.