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.