CoP2/Co2P Encapsulated in Carbon Nanotube Arrays to Construct Self-Supported Electrodes for Overall Electrochemical Water Splitting

Electrocatalytic water splitting is a desirable and sustainable strategy for hydrogen production yet still faces challenges due to the sluggish kinetics and rapid deactivation of catalysts in the oxygen evolution process. Herein, we utilized the metal-catalyzed growth technology and phosphating process to fabricate self-supported electrodes (Co_xP_y@CNT-CC) composed of carbon nanotube (CNT) arrays grown on carbon cloth (CC); thereinto, cobalt-based phosphide nanoparticles (Co_xP_y) are uniformly encapsulated in the cavity of the CNTs. After further optimization, when the nanoparticles are in the composite phase (CoP₂/Co₂P), CoP₂/Co₂P@CNT-CC served as catalytic electrodes with the highest activity and stability for electrocatalytic water splitting in an alkaline medium (1.0 M KOH). The as-prepared CoP₂/Co₂P@CNT-CC integrates the advantages of the abundant active sites and confinement effect of CNTs, imparting promising electrocatalytic activities and stability in catalyzing both hydrogen evolution reaction and oxygen evolution reaction. Remarkably, electrocatalytic water splitting cells assembled using CoP₂/Co₂P@CNT-CC electrodes as the cathode and anode, respectively, require a cell voltage of 1.55 V at 10 mA cm^-2, which is lower than that of the commercially noble Pt/C/CC and RuO₂/CC catalyst couple (1.68 V). Besides, a CoP₂/Co₂P@CNT-CC||CoP₂/Co₂P@CNT-CC system shows outstanding durability for a period of 100 h at 10 mA cm^-2. This work may provide new ideas for designing bifunctional electrocatalysts for applications in electrocatalytic water splitting.