Silicon Photoanode Modified with Work-function-tuned Ni@Fe_y Ni_1-y (OH)₂ Core-Shell Particles for Water Oxidation

The photoelectrochemical (PEC) water splitting determines by the light absorption and charge extraction/injection. Here, we dispersedly modified the core-shell structured Ni@Ni_y Fe_1-y (OH)₂ on Si photoanodes and in-situ electrochemically converted it to Ni@Ni_y Fe_1-y OOH to form a Si/SiO_x /Ni@Ni_y Fe_1-y OOH assembly, exhibiting the adjustable band bending and catalytic ability in water oxidation depending closely on the composition of Ni_y Fe_1-y OOH. Combining with the island-like dispersed distribution to maximize the light absorption and the Ni@Ni_y Fe_1-y shell as a high work function and a catalytic layer to simultaneously enlarge charge extraction and injection, the Si/SiO_x /Ni@Ni_0.7 Fe_0.3 OOH assembly achieved an onset potential of 1.0 V_RHE , a saturated current density of 35.4 mA cm^-2 and a more than 50 h stability in an electrolyte with pH 9 under AM1.5G simulated sunlight irradiation. Our findings suggested that regulating the charge energetics at Si-electrolyte interface by discontinuously modifying a composition-adjustable core-shell structure is a potential route to develop highly efficient PEC devices.