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Engineering defects in crystalline electrocatalysts is an effective approach to tailor the electronic structure and number of active sites, which are essential for the intrinsic activity of the hydrogen evolution reaction (HER). Unlike previously reported methods, we demonstrate a confinement effect using a mesoporous template for in situ fabrication of cationic W vacancies in asprepared ordered mesoporous tungsten phosphide (WP) nanostructures by adjusting the nonstoichiometric ratio of the precursor elements. With a plenty of W vacancies and ordered mesoporosity, the as-prepared catalyst WP-Mesop exhibits better catalytic performance than the catalysts without mesopores and/or vacancies. The WP-Mesop shows an ultralow overpotential of 175 mV in acid and 229 mV in alkaline at 100 mA cm −2 and stability of 48 h without structural collapse in both acid and alkaline media. Meanwhile, density functional theory calculations further reveal that the activation barrier for HER can be lowered by introducing cationic W vacancies. This strategy can be extended to generate cationic defects in other transition metal phosphides to improve their HER activities.

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The increased utilization ratio of solar energy by a PEC cell, which is significant in meeting the ever increasing demand of clean fuels and energy can be realized by fabricating the device into three dimensional structure. In this work, micrometer size Cu cone arrays was introduced to combine with electrodeposited Cu 2 O in the fabrication of photocathode. The acquired 3D Cu 2 O/Cu micro-cone arrays was proven to be more photoactive than the planar Cu 2 O/Cu foil structure. Under AM 1.5 illumination, the photocurrent density generated by the bare Cu 2 O/Cu micro-cone arrays reached a plateau value of −3.25 mA cm −2 in the linear sweep voltammetry test conducted from positive to negative. When protected by 20 nm ZnO plus 10 nm TiO 2 , the 3D photocathodes presented better stability and maintained a relatively large photocurrent at the same time. Thus, we have proposed a new structure in micrometer size that can improve the property of Cu 2 O photoelectrode.