Synergistic effect of Cu doping and NiPx/NiSey heterostructure construction for boosted water electrolysis

Heterostructure engineering and heteroatom-doping are effective strategies to develop efficient electrocatalyst for water splitting, however, the synergistic effect of these two strategies is seldom evaluated. In this work, micro-amount copper-doped nickle phosphide-selenide hetero-nanosheets electrocatalyst (Cu-NiPx/NiSey) is prepared on nickel foam by one-step phosphorus-selenization. The introduction of Cu facilitates the formation of multicomponent NiPx/NiSey heterostructures, and can also introduce a significant electronic modulation effect to produce high-valent Ni sites and NiOOH active species, benefiting for the oxygen evolution reaction (OER). The high intrinsic catalytic activity of nickle phosphide is compatible well with the high electrical conductivity of selenide, resulting in complementary enhancement of catalytic activity for Cu-NiPx/NiSey. As a result, the CuNiPx/NiSey electrodes exhibit extremely low overpotentials in 1 M KOH solution of 264 mV for OER at a current density of 100 mA cm � 2, and 69 mV for HER at 10 mA cm � 2. Importantly, when Cu-NiPx/NiSey is assembled as both electrodes, a high current density of 100 mA cm-2 can be achieved for over 60 h with only an ultra-low battery voltage of 1.71 V, exceeding most reported nickel-based bifunctional catalysts. The present work delivers a new strategy for designing and constructing effective bifunctional electrocatalysts for practical largescale water splitting.