Unravelling the Superior Photoelectrochemical Water Oxidation Performance of the Al-Incorporated CoOOH Cocatalyst-Loaded BiVO4 Photoanode

In photoelectrochemical (PEC) water splitting, the development of a highly efficient photoanode is a crucial part. BiVO4 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 BiVO4, which enhances the consumption of holes from the BiVO4 surface for water oxidation. With this connection, here the Al-doped CoOOH was loaded over the BiVO4 surface, which facilitates the water oxidation kinetics. The 15 mol % Al-doped CoOOH cocatalyst-incorporated BiVO4 photoanode delivered a high photocurrent density of 3.02 mA cm(-2), which was similar to 2.8-fold higher than that of BiVO4 (1.06 mA cm(-2)) and similar to 1.7-fold higher than that of BiVO4/CoOOH. The BiVO4/Al-CoOOH (15%) electrode displays an applied bias photon-to-current efficiency (ABPE) of 0.49% which is higher than those of BiVO4 and BiVO4/CoOOH, and it shows the transient decay time value of 1.83 s, which is similar to 2.3 and similar to 0.7-fold higher than those of BiVO4 and BiVO4/CoOOH; besides, the BiVO4/Al-CoOOH (15%) electrode utilizes 55% of the photogenerated holes for the water oxidation process which is 2.9-fold higher than that of BiVO4. Moreover, the BiVO4/Al-CoOOH electrode delivers a higher C-dl(99 mu F cm(-2)), which is similar to 1.4 and similar to 2.2-fold higher than those of BiVO4/CoOOH (69 mu F cm(-2)) and BiVO4 electrodes (44.5 mu F 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 BiVO4.