Mo-doped BiVO4 photoanodes synthesized by reactive sputtering.

We report a scalable and reproducible method for reactive co-sputtering of Mo-doped BiVO4 thin films with broad compositional control. Optimal photoanode performance is achieved at a Mo concentration of 3 at. %. Incorporation of Mo promotes growth of large grains and reduces majority carrier transport limitations, resulting in maximum AM1.5G photocurrent densities of 3.5 mA cm(-2) at 1.23 V vs. RHE in pH 6.8 buffer solution containing 0.1 M Na2 SO3 as a hole scavenger. Operation as a front-illuminated water oxidation photoanode is achieved by balancing the operational stability, catalytic activity, and parasitic optical absorption of a FeOOH oxygen evolution catalyst. FeOOH/Mo:BiVO4 thin film photoanodes enable water oxidation under the front-side illumination conditions used in integrated tandem water splitting devices.