Pentlandite Compound-Anchored CuSCN as a Stable Electrocatalyst in Highly Alkaline Solutions

Abstract

Copper thiocyanate (CuSCN) is an unexplored material for watersplitting reactions, and it is a well-known photocathode in dye-sensitized solar cells. For the first time, the electrochemical properties of CuSCN were investigated and used in overall water-splitting reactions. It is observed that when a negative potential is applied to CuSCN, it readily gets electrons from the circuit and gives them to the dissociated hydrogen radical (H + ), which in turn facilitates more hydrogen adsorption sites (H ad ) and evolves hydrogen gas. Despite this advantage, chalcogenide materials (CuSCN) are not stable in alkaline solutions (pH = 14), where the surface gets easily oxidized in the KOH electrolyte by forming an S�O bond. Therefore, to prevent oxidation and material dissolution, we passivated the CuSCN surface with FeCo. Interestingly, the deposition of FeCo on CuSCN forms a pentlandite compound anchoring CuSCN, which suppresses the oxidation of the CuSCN surface in KOH solution by interatomic coupling of crystal systems and avoids direct contact of CuSCN with the electrolyte. Also, the inductively coupled plasma results show that the material dissolution concentration is greatly reduced from 2.67:26 to 0.37:3.4 (Cu:S) for FeCo-passivated CuSCN surfaces. The full cell constructed using CuSCN30 || FeCo/CuSCN30 as the cathode and the anode exhibits 1.70 V at 50 mA/cm 2 and tremendous robustness at a high current density of 200 mA/cm 2 for 50 h.