Graphitic Carbon Nitride Decorated with CoP Nanocrystals for Enhanced Photocatalytic and Photoelectrochemical H₂ Evolution

Abstract

Polydispersed CoP nanoparticles in an orthorhombic phase were synthesized via a gas−solid reaction and then deposited over graphitic carbon nitride to build the CoP/g-C 3 N 4 (CoP−CN) heterostructure. Nanorod-like CoP nanoparticles with a length of 10−80 nm were connected to g-C 3 N 4 nanosheets to build an intimate face-to-face contact via their crystal planes of ( 011) and ( 211). This unique heterojunction hybrid exhibits superior photocatalytic and photoelectrochemical performances for H 2 evolution and photoelectrochemical response plus excellent overall water-splitting activity. The optimal sample of 3% CoP−CN composite achieved a superior hydrogen production rate at 1038.1 μmol h −1 g −1 when irradiated by simulated solar light, exhibiting a much higher photocurrent at 150 μA cm −2 compared to pure g-C 3 N 4 . Also, a larger anodic current density was detected during the photoelectrochemical hydrogen evolution reactions (PEC HERs) with enhanced applied bias photon-to-current efficiency, denoting a higher efficiency for PEC HER. The enhancements for photocatalytic and PEC HER activity are mainly attributed to the formation of intimate interfacial contact for better light absorption, stronger photoreductive potentials, and higher efficiency for charge separation and transfer. This study provides a proof-of-concept design and construction of effective cobalt-phosphide-based heterojunctions for hydrogen evolution and water-splitting applications.

Photocatalytic overall water splitting by graphitic carbon nitride

“…The development of OER cocatalyst is one of the primary bottleneck issues that constrain the OWS activities of GCN. As excellent candidates for electrocatalytic and photocatalytic OER reactions, 26,46,47 cobalt‐based materials have also been widely applied as photocatalytic cocatalysts for GCN to enhance the charge carrier transfer and decrease the kinetic limitation for surface oxygen evaluation 48–53 . For example, in the Pt/g‐C 3 N 4 system, N 2 evolution which originates from the oxidation of surface uncondensed amino groups (─NH) by holes was observed at the initial 80 h and the back reaction (water formation) proceeded on Pt species after turning off Xe lamp 35 .…”

“…As the bifunctional electrocatalytic OER and HER catalyst, CoP also has shown the great potential for OWS with reasonable stability. Its use as cocatalyst for GCN was further explored to promote oxygen evolution 51,53 . For example, Pan et al deposited CoP nanoparticles on two‐dimensional (2D) GCN through electrostatic interaction and introduced Pt nanoparticles on CoP/g‐C 3 N 4 through in situ photodeposition (Figure 2(A)).…”

Recent Advances in Metal–Organic Frameworks Derived Nanocomposites for Photocatalytic Applications in Energy and Environment

“…A variety of nanomaterials including metal nanoparticles (NPs), metal oxides, alloys, carbons and their composites have been explored as photocatalysts for hydrogen (H 2 ) generation by water splitting and photodegradation of organic pollutants in the wastewater. [ 1 , 2 , 3 , 4 ] Moreover, to mitigate the environmental damages caused by carbon dioxide (CO 2 ) emission, it is important to reduce the amount of CO 2 released into the atmosphere. [ 5 ] One plausible approach is to capture CO 2 from the industrial exhaust and chemically reduce it to carbon monoxide (CO) or other value‐added reusable hydrocarbons such as methane (CH 4 ), methanol (CH 3 OH), ethanol (C 2 H 5 OH) and many other chemicals.…”

Well-Designed 3D/2D/2D WO3/Bt/g-C3N4 Z-Scheme Heterojunction for Tailoring Photocatalytic CO2 Methanation with 2D-Layered Bentonite-Clay as the Electron Moderator under Visible Light

“…A number of structured materials have been explored during the last years; however, graphitic carbon nitride (g-C 3 N 4 ), a 2D layered semiconductor, has attracted many researchers due to its several advantages such as easy preparation through thermal decomposition of lower-cost precursors such as melamine, higher chemical and thermal stability, environmentally friendly, and much negative conduction band edge position. − However, the single semiconductor still suffers from the lower efficiency due to the higher recombination rate of photoinduced charge carriers, lower surface area, and unsuitable oxidation potential. , During the past years, considerable methods have been developed to improve g-C 3 N 4 efficiency, including noble/non-noble-metal doping and constructing heterojunctions. − However, fabrication of traditional type (II) composites of g-C 3 N 4 will result in the loss of reduction ability for the photocatalytic CO 2 reduction process …”