Houde She,Man Jiang,Pengfei Yue,Jingwei Huang,Lei Wang,Jianzhang Li,Gangqiang Zhu,Qizhao Wang
The performance of BiVO 4 for photoelectrocatalytic (PEC) water decomposition is commonly limited by reaction kinetics. In this work, NiS and CoS nanospheres were respectively loaded on BiVO 4 thin films (NiS/BiVO 4 and CoS/BiVO 4 composites) to improve its reaction kinetics for PEC water decomposition. Both physical and chemical properties of these composites were characterized by XRD , SEM, TEM, PL and UV-DRS. The photoelectric properties of the samples were verified by testing LSV , i-t, EIS and IPCE. The formation of the composites can effectively prevent the recombination of carriers and consequently accelerate the separation of electrons and holes. NiS/BiVO 4 and CoS/BiVO 4 can reach photocurrent of 2.1 mA cm −2 and 2.7 mA cm −2 under light respectively, at 1.23 V vs. RHE, which are 1.75 times and 2.25 times that of BiVO 4 (1.2 mA cm −2 ). The hydrogen production of the NiS/BiVO 4 and CoS/BiVO 4 photoanodes was 4.7 and 7.3 times higher than that of BiVO 4 photoanode, respectively.
A visible-light-Fenton-like reaction system was constructed for the selective conversion of peroxymonosulfate to sulfate radical. Au@CoS, when doped on monoclinic BiVO4{010} facets, promoted spatial charge separation due to the different energy band between the m-BiVO4{010} and {110} facets. The visible-light response of m-BiVO4was enhanced, which was attributed to the SPR effect of Au. And the photogenerated electrons were transferred from the m-BiVO4{010} facet to Au via a Schottky junction. Owing to higher work function, CoS was able to capture these photoelectrons with acceleration of the Co(Ⅱ)/Co(Ⅲ) redox, enhancing peroxymonosulfate conversion to sulfate radical (Co2++ HSO5−→ Co3++ •SO4−+ OH−). On the other hand, holes accumulated on m-BiVO4{110} facets also contributed to organics oxidation. Thus, more than 95% of RhB was degraded within 40 min, and, even after five cycles, over 80% of RhB could be removed. The radical trapping experiments and EPR confirmed that both the sulfate radical and photogenerated hole were the main species for organics degradation. UV-vis DRS, photoluminescence (PL) and photoelectrochemical analyses also confirmed the enhancement of the visible-light response and charge separation. In a pilot scale experiment (PMS = 3 mM, initial TOC = 151 mg/L, reaction time = 4 h), CoS-Au-BiVO4loaded on glass fiber showed a high mineralization rate (>60%) of practical wastewater.
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