Constructing Ti_(3)C_(2) MXene/ZnIn_(2)S_(4) heterostructure as a Schottky catalyst for photocatalytic environmental remediation

It is highly demanded to steer the charge flow in semiconductor for efficient photocatalytic environmental remediation.Herein,we designed an interfacial contact Ti_(3)C_(2) MXene/ZnIn_(2)S_(4) nanosheets(TC/ZISNS) Schottky heterostructure which could greatly enhance photogenerated charge separation of ZnIn_(2)S_(4) (ZIS).Through TEM and XPS measurement,the strong interface coupling between 2D ZnIn_(2)S_(4) nanosheets and 2D Ti_(3)C_(2) MXene were explained,and the formation of Schottky heterostructure was demonstrated by electrochemical method.To investigate the photocatalytic activity of as-prepared samples,the photocatalytic reduction of Cr(VI) and photocatalytic oxidation degradation tetracycline hydrochloride(TC-H) experiments were carried out.The results showed that the Schottky catalyst(10%-TC/ZISNS) possessed the optimum photocatalytic efficiency.Especially,the apparent rate constant of Cr(VI) reduction with 10%-TC/ZISNS was 3.9 times than that of pure ZIS.The photocatalytic performance of 10%-TC/ZISNS toward degradation rate of TC-H was 1.8 times than that of pure ZIS.Finally,a possible mechanism for great enhancement of visible-light driven photocatalytic activity in the TC/ZISNS system was provided.On the whole,this work provided a new insight on 2D/2D contact Schottky heterostructure for enhancing photocatalytic activity.

Tuning electronic properties of cobalt phthalocyanines for oxygen reduction and evolution reactions

Metal–phthalocyanines are a class of catalytically active materials promising in energy conversion and storage fields(e.g.,electrocatalysis).However,understanding and controlling the electrochemical properties in metal-phthalocyanine systems is challenging.Herein,we elucidate the electrocatalytic origins of a series of cobalt-phthalocyanine molecular catalysts and finetune their electronic properties at the atomic level,both experimentally and computationally.The interactions between the cobalt center and the local coordination environment are regulated by introducing either electron-donating or electron-withdrawing groups on the phthalocyanine ligand,and the spin-orbit splitting of cobalt is increased by~0.15 eV compared with the nonsubstituted ligand.Specifically,the aminated cobalt phthalocyanine-based electrocatalysts exhibit low free energies in the ratedetermining steps of the oxygen reduction(-1.68 eV)and oxygen evolution reactions(0.37 eV).This contributes to the high electrocatalytic activity(e.g.,a halfwave potential of 0.84 V and an overpotential of 0.30 V at 10 mAcm^(-2)),featuring a high selectivity of a four-electron pathway(i.e.,a negligible by-product of hydrogen peroxide).These catalysts also exhibit exceptional kinetic current density(Tafel slope of 100 mV dec^(-1))in oxygen reduction reactions,in addition to a superior power density(158 mWcm^(-2))and a high cycling stability(>1,300 cycles)in Zn-air batteries,outperforming the commercial Pt/C and/or RuO2counterparts.

Photocatalytic reduction of Cr(Ⅵ) over cinder-based nanoneedle in presence of tartaric acid: Synergistic performance and mechanism

Cr(Ⅵ) is a common heavy metal ion, which will seriously harm human body and environment.Therefore, the removal of Cr(Ⅵ) has become an attractive topic.In this work, cinder was used as a raw material to synthesize a nanoneedle material: γ-(AlOOH@FeOOH)(γ-Al@Fe).The physicochemical properties of γ-Al@Fe were thoroughly characterized, and its effectiveness as a catalyst for photocatalytic reduction of Cr(Ⅵ) was evaluated.The results showed that Cr(Ⅵ) could be efficiently reduced by γ-Al@Fe in the presence of tartaric acid(TA) under visible light.The variable factors on the reaction were investigated in detail, and the results showed that under optimal conditions(γ-Al@Fe 0.4 g/L, TA 0.6 g/L, pH 2), Cr(Ⅵ)was completely reduced within 7 min.Besides, scavenger experiments and EPR proved that O_(2)^(·-) and CO_(2)^(·-) played a significant role in the photocatalytic reduction of Cr(Ⅵ).TA acts as a sacrificial agent to trap the holes and generate strong reducing free radicals: CO_(2)^(·-).Dissolving O_(2) could react with electrons to generate O_(2)^(·-).This work discussed the performance and mechanism of photocatalytic reduction of Cr(Ⅵ) in detail, which provided a new idea for the resource utilization of solid waste and the treatment of heavy metal sewage.