Hydrogen evolution by a metal-free electrocatalyst

Abstract

Electrocatalytic reduction of water to molecular hydrogen via the hydrogen evolution reaction may provide a sustainable energy supply for the future, but its commercial application is hampered by the use of precious platinum catalysts. All alternatives to platinum thus far are based on nonprecious metals, and, to our knowledge, there is no report about a catalyst for electrocatalytic hydrogen evolution beyond metals. Here we couple graphitic-carbon nitride with nitrogen-doped graphene to produce a metal-free hybrid catalyst, which shows an unexpected hydrogen evolution reaction activity with comparable overpotential and Tafel slope to some of well-developed metallic catalysts. Experimental observations in combination with density functional theory calculations reveal that its unusual electrocatalytic properties originate from an intrinsic chemical and electronic coupling that synergistically promotes the proton adsorption and reduction kinetics.

One‐Dimensional Earth‐Abundant Nanomaterials for Water‐Splitting Electrocatalysts

“…For example, using the hydrogen‐bonded cyanuric acid melamine supramolecular complex as precursor, 1D C 3 N 4 nanorod were synthesized on a variety of different substrates, due to the interaction of free hydroxyl and amine groups of the supramolecular complex precursor 64. One early bench mark progress in this field was reported by the Qiao group, who reported the preparation of graphitic‐C 3 N 4 coupled with N‐doped graphene (C 3 N 4 @NG) 65. This metal‐free hybrid catalyst exhibited an unexpectedly high HER activity that was comparable to some of the well‐developed metallic catalyst.…”

“…c) Free‐energy diagram of HER on the surface of C 3 N 4 @NG under different H* coverage (1/3, 2/3 and 1 with the molecular configurations shown as insets) conditions. Reproduced with permission 65. Copyright 2014, Nature Publishing Group.…”

Twisted Aromatic Frameworks: Readily Exfoliable and Solution‐Processable Two‐Dimensional Conjugated Microporous Polymers

“…Furthermore, since such 2D polymers are synthesized by bottom‐up approaches, heteroatoms can be incorporated into the framework with relative ease, which provides an additional way to modulate their electronic structure and their properties. For example, the exchange of C atoms for N atoms in 2D organic frameworks has resulted in more efficient materials for energy applications, such as electrocatalysts for the oxygen reduction reaction (ORR),4 the hydrogen evolution reaction (HER),5 supercapacitors,6 and batteries 6a, 7…”

Carbon-Based Metal-Free Electrocatalysis for Energy Conversion, Energy Storage, and Environmental Protection

“…These studies confirm that observed excellent bifunctional catalytic performances are attributable to co-doping, coupled with the efficient mass and charge transfer of carbon catalysts with high active site exposure. High HER performance has also been achieved by coupling graphitic carbon nitride (g-C 3 N 4 ) with N-doped graphene (N-G) to combine intermolecular charge transfer with heteroatom-doping [132]. DFT calculations indicate an apparent electron transfer from conductive N-G to g-C 3 N 4 , leading to an electron-rich region on the g-C 3 N 4 layer and a hole-rich region on the N-graphene layer (Fig.…”

“…In 2013, Zhao et al [185] first reported N-doped graphite nanomaterials that were generated from direct pyrolysis of N-rich polymers as metal-free catalysts exhibiting comparable OER catalytic activities to non-precious metal catalysts in basic mediums. Subsequently, Zheng et al prepared C 3 N 4 @N-doped graphene as a metal-free electrocatalyst for sustainable and efficient H 2 production under acidic and alkaline conditions [132]. Thereafter, various heteroatomdoped carbon materials have been exploited as metal-free, active and stable OER and/or HER catalysts, as briefly described in previous reviews [4,11].…”