Metal-based catalysts for persulfate and peroxymonosulfate activation in heterogeneous ways: A review

Copper catalysts for radical and nonradical persulfate based advanced oxidation processes: Certainties and uncertainties

Structural doping is often used to prepare materials with high oxygen-ion conductivity and electrocatalytic function, but its wider application in solid oxide fuel cells (SOFCs) is still a major challenge. Here, a novel approach to developing materials with fast ionic conduction and high electrocatalytic activity is reported. A semiconductor-ionic heterostructure of perovskite Ba0.5Sr0.5Fe0.8Sb0.2O3-δ (BSFSb) and fluorite structure Sm0.2Ce0.8O2-δ (SDC) is developed. The BSFSb-SDC heterostructure exhibits a high ionic conductivity >0.1 S cm−1 (vs 0.01 S cm−1 of SDC) and achieves a remarkable fuel cell performance (>1000 mWcm−2) at 550 °C. It was found that the BSFSb-SDC has both electrolyte and electrode (cathode) functions with enhanced ionic transport and electrocatalytic activity simultaneously. When using BSFSb-SDC as an electrolyte, the interface energy-band reconstruction and charge transfer at particle level forming a built-in electric field (BIEF) and it make electronic confinement. The BIEF originates from the potential gradient due to differences in the electron density of BSFSb and SDC particles/grains facilitates ionic conduction at the interface of the BSFSb and SDC particles. This work provides a new insight in designing functional materials with high ionic conductivity and electrocatalytic function, which can be used both for energy conversion and storage device.

Promoted electrocatalytic activity and ionic transport simultaneously in dual functional Ba0.5Sr0.5Fe0.8Sb0.2O3-δ-Sm0.2Ce0.8O2-δ heterostructure

In this paper, we surprisingly found that the incorporation of unreducible metal oxides MxOy (M = Mg, Zn, Ca, Ba, Al) onto CuO hybrid magnetic nano ferric oxide (Cu@Fe3O4) may alter the reaction pathway in persulfate activation, and increase the reaction rate constant. The activation of peroxymonosulfate (PMS) by Cu@Fe3O4 led to a classic sulfate radical based oxidation process (SR-AOP) with an acetaminophen (ACE) degradation rate constant of 0.004 min−1, while 1O2-dominated nonradical oxidation process was disclosed in CuM@Fe3O4 with wildly fluctuated reaction rate constants from 0.003 to 0.242 min−1. Mechanism studies indicated that singlet oxygen (1O2) derived from the direct oxidation of superoxide anions radicals (O2 −) or the recombination of O2 − was the main reactive oxygen species (ROS) in CuM@Fe3O4/PMS system. A series of characterization experiments (pHpzc tests, XPS, H2-TPR, et al.) and DFT calculation disclosed that the addition of an unreducible metal M yielded many positive effects: (1) the formation of surface oxygen vacancies (OV) raised the zero point charge (pHpzc) of CuM@Fe3O4, thus enhanced the adsorption and activation of PMS; (2) promoting the generation of a new Cu species (Cu3+) on the surface of CuM@Fe3O4, which then participated in the generation of 1O2. The different reducibility of Cu3+ led to differences in the catalytic properties of CuM@Fe3O4. In addition, the effects of various water matrix species and the results of reusability experiment, mineralization experiment, and ecotoxicity test exhibited that CuM@Fe3O4/PMS system possessed excellent practical application value.

Tingting Zhang

Papers

Regulating activation pathway of Cu/persulfate through the incorporation of unreducible metal oxides: Pivotal role of surface oxygen vacancies