Dual-coupling ultrasmall iron-Ni₂P into P-doped porous carbon sheets assembled Cu_xS nanobrush arrays for overall water splitting

The challenge of simultaneously boosting two half-reactions for overall water splitting using a catalyst with excellent activity, good durability, and cost-effectiveness is still attracting great interest from the scientific community. Herein, a novel electrocatalyst was fabricated via a facile synthesis strategy for both the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER). The electrocatalyst was designed by dual-coupling iron and Ni₂P into P-doped porous carbon (PC) sheets, which were uniformly shelled over one-dimensional copper sulfide (Cu_xS) arrays to form a unique nanobrush architecture. The synergistic effects between the iron and ultrasmall Ni₂P nanoparticles offered a dominant contribution to the catalytic activities with a low required overpotential of 112.9 mV to reach 10 mA cm⁻² for the HER and 330 mV to reach 50 mA cm⁻² for the OER, superior to bare Cu_xS and Ni₂P@PC/Cu_xS. An electrolyzer cell originated from Fe-Ni₂P@PC/Cu_xS electrodes required a small cell voltage of 1.62 V at a current response of 10 mA cm⁻², which even interestingly surpassed recently reported ones. The excellent performance of the proposed Fe–Ni₂P@PC/Cu_xS material made it an innovative bifunctional candidate for overall water splitting applications.