Chinese Journal of Catalysis ›› 2018, Vol. 39 ›› Issue (3): 534-541.DOI: 10.1016/S1872-2067(17)62973-5

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Catalytic effects of[Ag(H2O)(H3PW11O39)]3- on a TiO2 anode for water oxidation

Jiansheng Li, Lei Wang, Wansheng You, Meiying Liu, Lancui Zhang, Xiaojing Sang   

  1. Institute of Chemistry for Functionalized Materials, Liaoning Normal University, Dalian 116029, Liaoning, China
  • Received:2017-09-30 Revised:2017-11-09 Online:2018-03-18 Published:2018-03-10
  • Contact: 10.1016/S1872-2067(17)62973-5
  • Supported by:

    This work was supported by the National Natural Science Foundation of China (21573099, 21601077, 21573100).

Abstract:

A[H3AgI(H2O)PW11O39]3--TiO2/ITO electrode was fabricated by immobilizing a molecular polyoxometalate-based water oxidation catalyst,[H3AgI(H2O)PW11O39]3- (AgPW11), on a TiO2 electrode. The resulting electrode was characterized by X-ray powder diffraction, scanning electron microscopy, and energy dispersive X-ray spectroscopy. Linear sweep voltammetry, chronoamperometry, and electrochemical impedance measurements were performed in aqueous Na2SO4 solution (0.1 mol L-1). We found that a higher applied voltage led to better catalytic performance by AgPW11. The AgPW11-TiO2/ITO electrode gave currents respectively 10 and 2.5 times as high as those of the TiO2/ITO and AgNO3-TiO2/ITO electrodes at an applied voltage of 1.5 V vs Ag/AgCl. This result was attributed to the lower charge transfer resistance at the electrode-electrolyte interface for the AgPW11-TiO2/ITO electrode. Under illumination, the photocurrent was not obviously enhanced although the total anode current increased. The AgPW11-TiO2/ITO electrode was relatively stable. Cyclic voltammetry of AgPW11 was performed in phosphate buffer solution (0.1 mol L-1). We found that oxidation of AgPW11 was a quasi-reversible process related to one-electron and one-proton transfer. We deduced that disproportionation of the oxidized[H2Ag(H2O)PW11O39]3- might have occurred and the resulting[H3AgOPW11O39]3- oxidized water to O2.

Key words: Water oxidation, Electrocatalysis, Photoelectrochemistry, TiO2, Polyoxometalate, Ag+ complex