Integrating Covalent Organic Framework with Transition Metal Phosphide for Noble‐Metal‐Free Visible‐Light‐Driven Photocatalytic H₂ Evolution

Abstract

2D covalent organic frameworks (COFs) are considered as one kind of the most promising crystalline porous materials for solar-driven hydrogen production. However, adding noble metal co-catalysts into the COFsbased photocatalytic system is always indispensable. Herein, through a simple solvothermal synthesis method, TpPa-1-COF, a typical 2D COF, which displays a wide light absorption region, is rationally combined with transition metal phosphides (TMPs) to fabricate three TMPs/TpPa-1-COF hybrid materials, named Ni 12 P 5 (Ni 2 P or CoP)/TpPa-1-COF. The incorporated TMPs can be served as electron collectors for accelerating the transfer of charges on TpPa-1-COF, thus the composites are demonstrated to be efficient photocatalysts for promoting water splitting. Benefitting from the richer surface reactive sites and lower H* formation energy barrier, the Ni 12 P 5 can most effectively improve the photocatalytic performance of the TpPa-1-COF, and the H 2 evolution rate can reach up to 31.6 µmol h −1 , approximately 19 times greater than pristine TpPa-1-COF (1.65 µmol h −1 ), and is comparable to the Pt/TpPa-1-COF (38.8 µmol h −1 ). This work is the first example of combining COFs with TMPs to construct efficient photocatalysts, which may offer new insight for constructing noble-metal-free COF-based photocatalysts.

Covalent Grafting of a Nickel Thiolate Catalyst onto Covalent Organic Frameworks for Increased Photocatalytic Activity

“…The hydrogen production rate of 3 wt % Pt/TpPa-1 was 5.90 mmol h À 1 g À 1 , lower than that for TpPa-1-SNi-10. Notably, the hydrogen evolution rate of TpPa-1-SNi-10 (10870 μmol g À 1 h À 1 ) was higher than that of most other reported TpPa-based photocatalytic systems, including TpDTz COF with Ni-thiolate (941 μmol h À 1 g À 1 ), [33] 12.5 % Ni 12 P 5 /TpPa-1 (3160 μmol h À 1 g À 1 ), [56] Ni(OH) 2 -2.5/TpPa-2 (1846 μmol h À 1 g À 1 ), [57] MoS 2 /TpPa-1 (5885 μmol h À 1 g À 1 ), [58] and 3 wt % Pt/TaPa-COF-(CH 3 ) 2 (8330 μmol h À 1 g À 1 ) [43] (Table S4). The enhanced crystallinity of TpPa-1 combined with covalent bonding between the Ni II thiolate cocatalyst and TpPa-1 facilitated transfer of the photo-generated electrons across the two-dimensional TpPa-1 network.…”

Femtosecond transient absorption spectroscopy investigation into the electron transfer mechanism in photocatalysis

“…[10][11][12] For instance, photocatalytic water splitting can produce hydrogen (H 2 ) from water, and photocatalytic carbon dioxide (CO 2 ) reduction can convert CO 2 into carbon monoxide (CO) and hydrocarbons. [13][14][15] Although photocatalysis seems to be an ideal approach for solar energy conversion, the low photocatalytic efficiency hinders its practical utilization.…”

Hydrogen-Induced Defective Crystalline Carbon Nitride with Enhanced Bidirectional Charge Migration for Persulfate Photoactivation

“…An advanced oxidation process (AOP) based on persulfate oxidation provides a promising approach to eliminate harmful pollutants in the aquatic environment because of the generation of sulfate radicals with a stronger oxidation potential (2.6 V) under a wider pH range than that of hydroxyl radicals. − Since pristine persulfate presents moderate oxidation capability for pollutant decomposition, numerous attempts have focused on breaking O–O bonds in persulfate for generating free radicals or directly degrading pollutants in the presence of additional energies [ultraviolet (UV), heat, ultrasonication, etc. ]. − Among these strategies, photocatalytic activation has attracted intense attention due to the synergistic oxidation of harmful contaminants by heterogeneous photocatalysts and activated persulfate with the aid of sustainable solar energy. − Currently, a major challenge of this approach is the lack of a suitable photocatalyst with satisfying activity and stability for activation reactions. − …”