Atomic‐Level Insight into Optimizing the Hydrogen Evolution Pathway over a Co₁‐N₄ Single‐Site Photocatalyst

Abstract

Knowledge of the photocatalytic H evolution mechanism is of great importance for designing active catalysts toward a sustainable energy supply. An atomic-level insight, design, and fabrication of single-site Co -N composite as a prototypical photocatalyst for efficient H production is reported. Correlated atomic characterizations verify that atomically dispersed Co atoms are successfully grafted by covalently forming a Co -N structure on g-C N nanosheets by atomic layer deposition. Different from the conventional homolytic or heterolytic pathway, theoretical investigations reveal that the coordinated donor nitrogen increases the electron density and lowers the formation barrier of key Co hydride intermediate, thereby accelerating H-H coupling to facilitate H generation. As a result, the composite photocatalyst exhibits a robust H production activity up to 10.8 μmol h , 11 times higher than that of pristine counterpart.

Artificial Photosynthesis with Polymeric Carbon Nitride: When Meeting Metal Nanoparticles, Single Atoms, and Molecular Complexes

“…However, the catalytic mechanisms of single transition‐metal atoms in these single‐atom metal/PCN composites during the photocatalytic reactions are still argued, depending on the transition metals existing in isolated or ligand‐coordinated single atoms. Wei and coworkers demonstrated a novel single site–based photocatalyst containing the atomically dispersed Co sites anchored on PCN via an atomic layer deposition (ALD) technique for efficient solar‐driven hydrogen evolution . With the X‐ray absorption near‐edge structure (XANES) simulations, the formation of “Co–N 4 ” was confirmed as the favorable structural configuration ( Figure a,b), and the formed Co–N 4 geometry was involved as an active center for activating HH bond formation process, consequently leading to the enhanced H 2 evolution efficiency (Figure c).…”

“…” b) Top view of the model structures: “Co 1 –N 4 ,” “Co 1 –N 2 ,” “Co 1 –N 3 C 2 .” c) Proposed photocatalytic H 2 evolution mechanism. Reproduced with permission . Copyright 2017, Wiley‐VCH.…”

“…In this structure, the coordinative Ni(I)N bonds acted as the chemical adsorption sites for molecular O 2 and promoted photoexcited electrons transfer from PCN into the reaction sites to activate the molecular O 2 . Wei and coworkers demonstrated that with atomically dispersed Co sites anchored on PCN, the formed Co 1 –N 4 geometry would act as an active center for efficient photocatalytic hydrogen evolution . The coordinated single metal atoms can modify the electronic properties of the PCN framework, rending PCN as the potential photocatalysts for pure water splitting.…”

The Role of Supported Atomically Distributed Metal Species in Electrochemistry and How to Create Them

“…Although non‐noble transition metal based single dispersed electrocatalysts for ORR application have been reported frequently, anchoring the stable transition‐metal atoms (e. g. nickel and iron) is not as popular in HER . Xue et al.…”

“…Although non-noble transition metal based single dispersed electrocatalysts for ORR application have been reported frequently, anchoring the stable transition-metal atoms (e. g. nickel and iron) is not as popular in HER. [64] Xue et al reported a strategy to fabricate isolated nickel/iron atoms anchored on graphdiyne. [65] The findings identified very narrow size distributions of both nickel (1.23 Å) and iron (1.02 Å), and the atomic catalysts have high catalytic activity and stability for HER.…”