3D Architectures of Quaternary Co‐Ni‐S‐P/Graphene Hybrids as Highly Active and Stable Bifunctional Electrocatalysts for Overall Water Splitting

Abstract

Developing low-cost, highly active, and stable bifunctional electrocatalysts is a challenging issue in electrochemical water electrolysis. Building on 3D architectured electrocatalysts through structural and compositional engineering is an effective strategy to enhance catalytic activities as well as stability and durability. Herein, 3D architectures of quaternary Co-Ni-S-P compounds coupled with graphene ((Co 1−x Ni x )(S 1−y P y ) 2 /G) electrocatalysts are proposed, in which nanosheets are self-assembled to form 3D architectures with round and flat doughnut-like shapes, toward overall water splitting. Benefiting from the 3D architectures and Ni, P substitution, (Co 1−x Ni x )(S 1−y P y ) 2 /G exhibits superior electrocatalytic activities with low overpotentials of 117 and 285 mV at 10 mA cm −2 and Tafel slopes of 85 and 105 mV dec −1 for hydrogen and oxygen evolution reactions, respectively, in alkaline media. In addition, minimal increases in overpotential are observed, even after the 10 000th voltammetric cycle and continuous chronopotentiometric testing over 50-100 h, confirming the high stability and durability of (Co 1−x Ni x )(S 1−y P y ) 2 /G. When used as both cathode and anode, (Co 1−x Ni x )(S 1−y P y ) 2 /G achieves excellent overall water splitting performance with a cell potential as low as 1.65 V, reaching a current density of 10 mA cm −2 with no obvious decay after 50 h, demonstrating that (Co 1−x Ni x )(S 1−y P y ) 2 /G is an efficient bifunctional electrocatalyst for overall water splitting.

Highly Efficient Hydrogen Evolution from a Mesoporous Hybrid of Nickel Phosphide Nanoparticles Anchored on Cobalt Phosphosulfide/Phosphide Nanosheet Arrays

“…First, nickel (Ni) foam with a size of 1 × 2 cm 2 was immersed in 0.05 m Co(NO 3 ) 2 × 6H 2 O aqueous solution for electrodeposition of the Co‐species nanosheets array, which is composed of Co(OH) 2 , Co 3 O 4 , and CoO (Figure S1, Supporting Information) . Second, the electrodeposited sample was thermally sulfurized in a tube furnace at 450 °C for 1 h in argon atmosphere to form cobalt sulfide (CoS 2 ) nanosheet arrays . Third, the Ni ink was modified on the surface of the as‐obtained CoS 2 nanosheet arrays/Ni foam, followed by thermal phosphorization at 450 °C for 1 h with red phosphorus (P) powder supplied at the upstream under argon protection.…”

Engineering Ternary Pyrite‐Type CoPS Nanosheets with an Ultrathin Porous Structure for Efficient Electrocatalytic Water Splitting

“…[17] The XPS study confirms that the UPNSs catalyst is partially oxidized to the Co (oxy)hydroxide species, which is always found in Co-based catalysts for OER. [41] Based on the above analysis, surface (oxy)hydroxides are in-situ generated as the active phase during the OER process. After long-term electrolysis, the peak at~322 cm À 1 of the CoPS [10] disappears, and a new peak at~677 cm À 1 is seen, which is assigned to the CoOOH.…”

Microstructural Engineering of Heterogeneous P−S−Co Interface for Oxygen and Hydrogen Evolution

“…Transition metal phosphides (TMPs) and transition metal chalcogenides (TMDs) have been widely concerned, and indicated as high active electrocatalysts in OER and hydrogen evolution reaction (HER) . Recent research shows that metal phosphosulfide composite has much more superior electrocatalytic activity than its individual components .…”