Stabilizing Silicon Photocathodes by Solution-Deposited Ni–Fe Layered Double Hydroxide for Efficient Hydrogen Evolution in Alkaline Media

An important pathway toward cost-effective photoelectrochemical (PEC) solar water-splitting devices is to stabilize and catalyze silicon (Si) photocathodes for hydrogen evolution reaction (HER), especially in alkaline solutions. To date, the most stable Si photocathode in alkaline media is protected by the atomic layer deposited (ALD) dense TiO 2 layer and catalyzed by noble metal-based catalysts on top. However, the ALD process is difficult to scale up, and the noble metals are expensive. Herein, we report the first demonstration of using a scalable hydrothermal method to deposit earth-abundant NiFe layered double hydroxide (LDH) to simultaneously protect and catalyze Si photocathodes in alkaline solutions. The NiFe LDH-protected/catalyzed p-type Si photocathode shows a current density of 7 mA/cm 2 at 0 V vs RHE, an onset potential of ∼0.3 V vs RHE that is comparable to that of the reported p–n + Si photocathodes, and durability of 24 h at 10 mA/cm 2 in 1 M KOH electrolyte.