Unravelling the Superior Photoelectrochemical Water Oxidation Performance of the Al-Incorporated CoOOH Cocatalyst-Loaded BiVO<sub>4</sub> Photoanode
Antonysamy Soundarya Mary, C. Murugan, P. Murugan, Alagarsamy Pandikumar
Abstract
In photoelectrochemical (PEC) water splitting, the development of a highly efficient photoanode is a crucial part. BiVO 4 is one of the leading photoanode materials, but its efficiency usually suffers from slow surface water oxidation kinetics and a higher charge recombination process. The loading of the oxygen evolution cocatalyst with a high electrocatalytic activity is an effective method for avoiding these issues in BiVO 4, which enhances the consumption of holes from the BiVO 4 surface for water oxidation. With this connection, here the Al-doped CoOOH was loaded over the BiVO 4 surface, which facilitates the water oxidation kinetics. The 15 mol % Al-doped CoOOH cocatalyst-incorporated BiVO 4 photoanode delivered a high photocurrent density of 3.02 mA cm –2, which was ∼2.8-fold higher than that of BiVO 4 (1.06 mA cm –2 ) and ∼1.7-fold higher than that of BiVO 4 /CoOOH. The BiVO 4 /Al-CoOOH (15%) electrode displays an applied bias photon-to-current efficiency (ABPE) of 0.49% which is higher than those of BiVO 4 and BiVO 4 /CoOOH, and it shows the transient decay time value of 1.83 s, which is ∼2.3 and ∼0.7-fold higher than those of BiVO 4 and BiVO 4 /CoOOH; besides, the BiVO 4 /Al-CoOOH (15%) electrode utilizes 55% of the photogenerated holes for the water oxidation process which is 2.9-fold higher than that of BiVO 4 . Moreover, the BiVO 4 /Al-CoOOH electrode delivers a higher C dl (99 μF cm –2 ), which is ∼1.4 and ∼2.2-fold higher than those of BiVO 4 /CoOOH (69 μF cm –2 ) and BiVO 4 electrodes (44.5 μF cm –2 ), respectively. The first-principles calculations revealed that Al-CoOOH requires a lower overpotential (3.53 V) than CoOOH (4.29 V), and the introduction minimum amount of Al species could stabilize the CoOOH, thus enhancing the PEC performance of BiVO 4 .