查看更多>>摘要：Bi-defective g-C3N4 (K and -C≡N) nanorod arrays with favorable light absorption through multiple light scattering/reflections were designed for photocatalytic N2 reduction. The highest record of NH3 production, 23.5 mmol/(h · g_(cat)), was achieved when dual defects are present at the nanoarrays without any cocatalysts, which is about two orders higher than its counterpart. The N2 reduction rate is proportional to -C≡N, unveiling its role as active sites. Its synergistic effect with K was observed. Theoretical calculations support that -C≡N site is crucial to N2 activation by donating electrons, while cation like K center traps electrons. Consequently modification with such dual defects in conjunction with nanoarray configuration creates a favorable electron-dominated structure to overcome the energy barrier for activating inert nitrogen, enhancing charge separation and light absorption effectively. The present work underlines the impetus of defects engineering and nanoarray configuration for the rational design of active photocatalysts for efficient N2 fixation.
查看更多>>摘要：Herein, using manganese dioxide octahedral molecular sieve (Mn-OMS) as the catalyst, we investigate how pollutant electron property affects the peroxymonosulfate (PMS) activation mechanism. More than 95% of electron-rich pollutants are degraded in the Mn-OMS/PMS system after 30 min reaction time, but oxidative decomposition of electron-poor pollutants takes at least 150 min. This difference in reaction rate is proved to be pollutant-dependent. We then combine multiple methods to cross-validate the PMS activation mechanism, including the quenching test, EPR characterization, solvent-exchange experiment, PMS decomposition rate test, and electrochemical analysis. Catalyst-mediated electron transfer is determined as the main activation mechanism for electron-rich pollutants degradation, while removal of electron-poor pollutants relies on singlet oxygen (~1O2) and/or radicals. Additionally, the PMS activation mechanism depends on whether H2O or pollutants or low-valence Mn ions preferentially transfer electrons to the adsorbed PMS. This work provides mechanistic insights into the effect of pollutants type on PMS activation.
查看更多>>摘要：A strategy of regulating the basicity of perovskite oxygen ions by cation doping is proposed to design cathode materials with high catalytic activity for solid oxide electrolysis cells (SOECs). Specifically, a series of Sr2Fe_(1.5-x)ZrxMo_(0.5)O_(6-δ) (SFZxM) perovskites are developed and characterized for its electrocatalytic activity and oxygen ions basicity to investigate the effect on electrochemical performance. The experimental results show that the single cell prepared with the Sr2Fe_(1.3)Zr_(0.2)Mo_(0.5)O_(6-δ) (SFZ2M) cathode reaches a current density of 1.85 A cm~(-2) at 1.8 V and 800 °C and exhibits good stability over 120 h under CO2 atmosphere. Combined with first-principles calculations, it is further confirmed that the introduction of low-electronegativity ions can improve the oxygen ions basicity and also increase the oxygen vacancy concentration of the cathode, thereby realizing the improvement of electrochemical performance. Thus, this strategy provides new insights into designing electrodes for direct CO2 electrolysis as well as other electrochemical catalysis.
查看更多>>摘要：Electro catalytic ammonia (NH3) conversion under ambient atmosphere is crucial to mimic the nature's nitrogen cycle. But currently it is always interrupted by the HER process which is more competitive. Herein, we tactically cultivate a series of incompletely etched Ti3AlC2 MAX / Ti3C2 MXene based heterostructure catalysts whose composition can be finely tuned through regulation of the LiF percentage in mixed chemical etching agent. Notably, the surface potential difference between MAX and MXene is ～40 mV, indicating that the electron can be readily transferred from MAX to MXene across the interfaces, which is favorable for N2 fixation, yielding an outstanding Faradic efficiency of 36.9%. Furthermore, density functional theory calculations reveal the billiard-like catalysis mechanism, where the intermediates are alternatively adsorbed on MAX or MXene surfaces. Meanwhile, the rate-determining step of *NH → *NH2 possesses an energy barrier of 0.96 eV on the hetero-interface which follows associative distal mechanism. This work opens a new frontier of heterostructured catalyst for balancing electrical conductivity and catalytic activity in electrocatalysis.
查看更多>>摘要：H2O2 production by 2 electron water oxidation reaction (2e~- WOR) is a promising approach, but still lacks mechanistic studies especially from a dynamic point of view. The interfacial water behavior on the solid/liquid interface is believed to play a crucial role in WOR activity. Here, F modification was used to accommodate the structure and dynamic process of interfacial water on WO3 surface and boost the 2e-WOR activity. Electrochemical measurement, Raman spectra and computational techniques were used to investigate the mechanism. F modification was proved to guide the dipole moments of interfacial water molecules towards WO3 surface, meaning more difficult to flip interfacial water molecules to perform the first step of WOR, in turn resulting in easy desorption of HO* and O-O*, thus benefiting for 2 e~- WOR. This work paves a novel insight to understand mechanism of 2 e~- WOR and rationally design the electrocatalysts for H2O2 production from water.
查看更多>>摘要：A composite electrode of manganese oxide (MnO2) incorporated with iron oxide (α-FeOOH) was synthesized for arsenite (As(III)) oxidation and subsequent arsenate (As(V)) electrosorption. The crystal structure and chemical state of MnO2 polymorphs were characterized by X-ray diffraction (XRD), scanning electron microscope (SEM), X-ray photoelectron spectroscopy (XPS), and BET surface area. The redox couple of Mn(III)/Mn(IV) mediated the catalytic electron transfer with respect to As(III)/As(V) redox equilibrium. The Mn site contributed a high diffusive current to the redox capacitance, meanwhile the Fe site better provided the double-layer capacitive deionization for arsenic species. Electrolysis of arsenite under constant anodic potential mode (+1.0 V vs. Ag/AgCl) enabled assess the performance of the electrodes. Among the polymorphs, γ-Mn_(0.2)Fe_(0.8)O exhibited the best arsenic adsorption capacity of 48 mg-As g~(-1), compared to that of α-FeOOH NPs (15 mg-As g~(-1)) and γ-MnO2 (7 mg-As g~(-1)), based on multilayer Langmuir adsorption model.
查看更多>>摘要：A self-supported chainmail electrocatalyst is developed by embedding graphitic carbon layer-encapsulated Co nanoparticles on N-doped carbonized wood (Co@NCW) as an advanced air cathode for rechargeable Zn-air batteries (ZABs). The NCW with open aligned microchannels facilitates O2 and electrolyte permeation and transportation, while the uniformly distributed graphitic carbon layer-encapsulated Co nanoparticles on NCW featuring fast electron transfer kinetics provide abundant triphase reaction sites for oxygen reduction reaction (ORR) and oxygen evolution reaction (OER). The Co@NCW exhibits a half-wave potential of 0.89 V vs. reversible hydrogen electrode (RHE) for ORR outperforming the Pt/C (0.85 V vs. RHE) and an overpotential of 410 mV for the OER (10 mA cm~(-2)) comparable to RuO2 (340 mV). A rechargeable ZAB assembled with Co@NCW presents a power density of 47.5 mW cm~(-2) and excellent stability at 5 mA cm~(-2) for 240 h. This work provides an effective strategy to fabricate a practically applicable oxygen electrode for ZABs.
查看更多>>摘要：Protonic ceramic fuel cells (PCFCs) have generated significant interest due to their weak temperature dependence and efficient energy conversion. However, traditional cathode materials show poor electrocatalytic activity at a low operating temperature due to their intrinsically slow proton diffusion, which is a long-standing issue that limits the output performance of PCFCs. Herein, the strategy of fluorinating a perovskite cathode is proposed for promoting proton transfer within the bulk of the cathode. This strategy is demonstrated in a fluorinated BaCo_(0.4)Fe_(0.4)Zr_(0.1)Y_(0.1)O_(3-δ) (BCFZY) perovskite, which reveals a reduced polarization resistance and enhanced PCFC output performance, superior to those of newly reported PCFCs. Combing the experimental characterization and theoretical calculations, we found that the performance improvement was ascribed to the strong inductive effect of F~-, which can increase the polarity the M-O bonding and decrease the O · · · H interaction, thus boosting the production of protonic defects and increasing the protonic diffusion coefficient.
查看更多>>摘要：Rational design of effective bifimctional inexpensive oxygen electrocatalyst is highly important for Zn-air batteries (ZABs), which can accelerate both oxygen reduction/evolution reactions at the oxygen electrode. Herein, we present the formation of hierarchical hollow frameworks of dual-sided Fe/Fe3C@N-doped carbon nanotubes (FNCHFs) through a template-engaged method. Benefitting from the synergistic effect between the robust hollow frameworks and in-situ grown dual-sided N-doped carbon nanotubes, the FNCHF electrocatalyst presents enhanced mass/electron transport with high structural stability. As a result, the FNCHFs based bifimctional oxygen electrode demonstrates a desirable oxygen electrocatalytic activity and stability with a half-wave potential of 0.863 V for oxygen reduction and an overpotential of 340 mV to reach the current density of 10 mA cm~(-2) for oxygen evolution. The corresponding ZAB exhibits a high peak power density of 206 mW cm~(-2), a high specific capacity of 781 mAh g_(Zn)~(-1), and a g°°d cycling stability more than 300 h.
查看更多>>摘要：Hydroxyl radicals always play important role in the photocatalytic degradation of pollutants and thus lots of efforts have been made to enlarge their amount. Herein, BiOCl photocatalysts with different surface hydroxyl groups amount are synthesized using ionic liquid self-combustion (C-BiOCl) and hydrothermal method (H-BiOCl) to deep understand the roles of hydroxyl radicals in toluene mineralization. It is found that hydroxyl radicals in H-BiOCl have reverse inhibitory effect on the ring-opening reaction in the photocatalytic mineralization process of toluene and C-BiOCl exhibits more excellent ability and stability in mineralizing toluene. The reason is that C-BiOCl lacking hydroxyl groups can selectively generate benzoic acid by holes and superoxide anion radicals;; while H-BiOCl with large number of hydroxyl groups will lead to the production of hydroxyl radicals and phenolic intermediates, which will preferentially cover active sites such as oxygen vacancies, thereby reducing the performance and stability of the catalyst.
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