Nanoporous 6H-SiC Photoanodes with a Conformal Coating of Ni–FeOOH Nanorods for Zero-Onset-Potential Water Splitting

[Image: see text] A surface-nanostructured semiconductor photoelectrode is highly desirable for photoelectrochemical (PEC) solar-to-fuel production due to its large active surface area, efficient light absorption, and significantly reduced distance for charge transport. Here, we demonstrate a facile approach to fabricate a nanoporous 6H-silicon carbide (6H-SiC) photoanode with a conformal coating of Ni–FeOOH nanorods as a water oxidation cocatalyst. Such a nanoporous photoanode shows significantly enhanced photocurrent density (j(ph)) with a zero-onset potential. A dendritic porous 6H-SiC with densely arranged holes with a size of ∼40 nm on the surface is fabricated by an anodization method, followed by the hydrothermal deposition of FeOOH nanorods and electrodeposition of NiOOH. Under an illumination of AM1.5G 100 mW/cm(2), the Ni–FeOOH-coated nanoporous 6H-SiC photoanode exhibits an onset potential of 0 V versus the reversible hydrogen electrode (V(RHE)) and a high j(ph) of 0.684 mA/cm(2) at 1 V(RHE), which is 342 times higher than that of the Ni–FeOOH-coated planar 6H-SiC photoanode. Moreover, the nanoporous photoanode shows a maximum applied-bias-photon-to-current efficiency (ABPE) of 0.58% at a very low bias of 0.36 V(RHE), distinctly outperforming the planar counterpart. The impedance measurements demonstrate that the nanoporous photoanode possesses a significantly reduced charge-transfer resistance, which explains the dramatically enhanced PEC water-splitting performance. The reported approach here can be widely used to fabricate other nanoporous semiconductors for solar energy conversion.