Single Nickel Atoms Anchored on Nitrogen-Doped Graphene as a Highly Active Cocatalyst for Photocatalytic H₂ Evolution

Abstract

Earth-abundant nickel is a typical non-noble-metal cocatalyst used for photocatalytic hydrogen evolution (PHE). Ni nanoparticles, however, tend to aggregate during the hydrogen production process, significantly lowering their PHE activity. To avoid aggregation, we used single atom form Ni and anchored them on vacancies in nitrogen-doped graphene (Ni-NG) as a cocatalyst for PHE. We demonstrated that Ni-NG is a robust and highly active cocatalyst for PHE from water. With only 0.0013 wt % of Ni loading, the PHE activity of composite Ni-NG/CdS photocatalyst improves by 3.4 times compared to that of NG/CdS, and it does not decay even after 10 rounds of 5-hour running. The quantum efficiency of Ni-NG/CdS for PHE reaches 48.2% at 420 nm, one of the highest efficiencies for non-noble-metal-based cocatalysts reported in the literature. Photoluminescence spectral analyses and electrochemical examinations indicated that Ni-NG coupled to CdS serves not only as an electron storage medium to suppress electron–hole recombination but also as an active catalyst for proton reduction reaction. Density functional theory calculations show that the high activity of Ni-NG/CdS composite results from the single Ni atoms trapped in NG vacancies, which significantly reduces the activation energy barrier of the hydrogen evolution reaction. This research may be valuable for developing robust and highly active noble metal free cocatalysts for solar hydrogen production.

TriQuinoline

“…Recent advances in analytical techniques have enabled the detailed analysis of individual heteroatom dopants in graphitic materials, which allows for identification of the distinctive nature of graphitic- and pyridinic-nitrogen sites 18–21 . Various methods have emerged for the preparation of graphitic materials with structural defects surrounded by three pyridinic nitrogens 22–24 , paving the way for the introduction of metal cations to impart, e.g., particular catalytic functionality 25,26 with prospective applications in energy conversion 27 and biocompatible catalysis 28 . However, the introduction of structurally defined defects is often random, and precise control over the position of such defects remains elusive.…”

Hollow Mesoporous Carbon Sphere Loaded Ni–N4 Single‐Atom: Support Structure Study for CO2 Electrocatalytic Reduction Catalyst

“…[7] Recently, lots of Ni-N x catalysts have been reported to support on carbon matrix with different morphologies through various synthetic strategy, including pyrolysis of MOFs [8] or polymeric precursors [9] and postmodification of N-doped graphite materials. [10] Many experiments and theoretical calculations have been made to identify the important role of Ni-N x active sites in CO 2 RR. [11] But the effect of the support geometrical structure of Ni-N x catalysts on CO 2 RR performance has been ignored.…”

Recent Progress in Non‐Precious Metal Single Atomic Catalysts for Solar and Non‐Solar Driven Hydrogen Evolution Reaction

“…Zhao et al reported that Ni could be anchored in N-doped graphene in both SV+3N and DV+4N vacancy centers (SV = single vacancy, DV = double vacancies), forming stable Ni-N 3 and Ni-N 4 active sites with Ni valance at +0.75 and +0.85, respectively, Figure 5. [84] Ni atom in SV-3N center not only showed very low |∆ H G * | for H adsorption on Ni, but reduced the H adsorption |∆ H G * | on N. As a result, the activation energy barrier of HER was notably reduced.…”