Efficient Noble-Metal-Free Co-NG/TiO₂ Photocatalyst for H₂ Evolution: Synergistic Effect between Single-Atom Co and N-Doped Graphene for Enhanced Photocatalytic Activity

Abstract

Photocatalytic water splitting for H2 evolution is appealing for transforming solar energy into clean chemical fuel. This technique generally requires noble metals as H2 evolution cocatalysts to facilitate efficient cleavage of water. Herein, we report a noble-metal-free TiO2 nanobelts composite photocatalyst, in which TiO2 nanobelts are supported by nitrogen-doped graphene coordinated with a single Co atom (Co-NG). The results show that Co-NG is an efficient cocatalytst for the photocatalytic H2 production over TiO2. The optimal amount of Co-NG loading is found to be 3.5 wt %, showing a H2 evolution rate of 677.44 μmol h–1 g–1 under illumination of AM 1.5 G simulated sunlight, which is close to that of platinized TiO2 nanobelts and 2.6 and 31.2 times greater than that of 3.5 wt % NG/TiO2 nanobelts composite and pure TiO2 nanobelts, respectively. The significantly improved photocatalytic activity is ascribed to the remarkable synergistic effect between single-atom Co and N-doped graphene, which serve as effective H+ reduction sites and efficient electron acceptors, respectively. Besides, the Co-NG cocatalyst also effectively retards the recombination of photoinduced charge carriers and leads to a prolonged lifetime of charge pairs. This study reveals that Co-NG is an up-and-coming candidate as cocatalyst for development of cost-effective photocatalysts for efficient solar-driven H2 evolution.

Recent Achievements in Development of TiO2-Based Composite Photocatalytic Materials for Solar Driven Water Purification and Water Splitting

“…Yi et al [118] synthesized a composite in which TiO 2 nanobelts were supported by N-doped graphene (NG) coordinated with a single Co atom to replace noble metals with a cost-effective photocatalyst. Under simulated solar irradiation ( Figure 14), e − /h + pairs are formed.…”

Inside‐and‐Out Semiconductor Engineering for CO2 Photoreduction: From Recent Advances to New Trends

“…Combining single‐atomic sites into 2D ultrathin nanosheets is a promising approach to integrate their advantages. [ 453 ] Di et al [ 454 ] reported the successful synthesis of Bi 3 O 4 Br atomic layers with well‐dispersed single cobalt atoms (Figure 28c). It was proven that the valence state of isolated and highly dispersed single Co atom is close to +2 (Figure 28d,e), because the position of Co K‐edge absorption edge was close to that of CoO rather than Co foil in Co–Bi 3 O 4 Br–1.…”

Ultrahigh Photocatalytic CO2 Reduction Efficiency by Single Metallic Atom Oxide on TiO2

“…In recent years, the atomic-scale con gurations of single-sites have been developed, i. e. single-atom, single-metal-atom-oxide and single-unit-cell [60][61][62][63]. Following this route for TiO 2 , potential active sites can be designed as a single site anchored on TiO 2 surface [64][65][66][67][68][69][70][71][72][73][74][75], and atomic step site on TiO 2 has been veri ed to enhance electron-transfer and molecular capture capability [76][77][78][79][80] .…”