Highly Efficient Photoelectrochemical Water Oxidation Using Cs2AgMCl6 (M = In,Bi,Sb) Halide Double Perovskites

In this work, stable Cs2AgMCl6(M = Bi,In,Sb) double perovskite materials are successfully employed as photoanodes for solar water oxidation. These materials show an extraordinary oxidative stability, where Cs2AgInCl6 and Cs2AgBiCl6 are stable between 0 and 1.2 V (vs Ag-AgCl) and Cs2AgSbCl6 between 0 and 0.75 V (vs Ag-AgCl) over 100 cycles of electrochemical cycling. This enables us to employ these materials for photoelectrochemical (PEC) water oxidation in CH3CN and H2O, with and without IrOx cocatalyst. All three materials show PEC activity, with Cs2AgInCl6 showing the highest performance. At 1.23 V (vs a reversible hydrogen electrode), a photocurrent density of 0.5 mA cm-2 is observed, and with an applied overpotential of 600 mV, the photocurrent increases to about 0.75 mA cm-2. From the band gap of Cs2AgInCl6, the estimated theoretical maximum current is around 0.82 mA cm-2. So, Cs2AgInCl6-coated IrOx gives nearly 60% and about 90% of the theoretical maximum photocurrent at zero bias and at an applied overpotential, respectively. The device is shown to be stable and reproducibility is confirmed.