Synergistic Effects of Nitrogen Doping on MXene for Enhancement of Hydrogen Evolution Reaction

Abstract

Earth-abundant, nonprecious, and efficient electrocatalysts for effective hydrogen evolution reaction (HER) are crucial for future large-scale green energy production. Low-cost two-dimensional MXenes have been widely studied in energy-storage devices owing to their unique chemical and physical properties and have recently attracted scientists in the electrocatalysis field. Nevertheless, their electrocatalytic activity still remains unsatisfactory. Herein, we present a facile and general strategy using ammonia heat treatment to enhance the hydrogen evolution catalysis of Ti 3 C 2 T x MXenes by modification with a nitrogen heteroatom. Importantly, our approach is focused on revealing: (1) the contribution of all possible incorporated N species including Ti−N, N−H, and N in O−Ti−N, rather than considering only that of Ti−N x motifs as previously reported for N-doped MXene electrocatalysts, and their role in inducing a change in the electronic configuration of the as-prepared catalysts, which then leads to increased electrical conductivity and improved intrinsic catalytic reactivity; and (2) the importance of controlling the proper amount of N obtained at a suitable calcined temperature to assist the shift of the Gibbs free energy for hydrogen adsorption (ΔH ad *) approaching 0 eV (ideal value), as proved by the density functional theory. Moreover, experimental findings indicate that nitrogen-doped Ti 3 C 2 T x annealed at 600 °C shows superior improved HER electrocatalytic performance compared to pristine Ti 3 C 2 T x , with an onset potential of −30 mV and an overpotential as low as 198 at 10 mA cm −2 , as well as a much smaller Tafel slope of 92 mV dec −1 .

Synthesis of Ru‐Doped VN by a Soft‐Urea Pathway as an Efficient Catalyst for Hydrogen Evolution

“…Hydrogen energy has been regarded as an ideal energy carrier alternative to the conservative fossil fuels for its high gravimetric energy density and environmental benefit. Currently, water electrolysis is proposed to be a promising route to produce hydrogen with high purity . The hydrogen evolution reaction (HER) occurred on cathode in electrolytic bath is a key reaction in water splitting, highly dependent on the HER activities of electrocatalysts .…”

“…Currently, water electrolysis is proposed to be a promising route to produce hydrogen with high purity. [1][2][3][4][5][6] The hydrogen evolution reaction (HER) occurred on cathode in electrolytic bath is a key reaction in water splitting, highly dependent on the HER activities of electrocatalysts. [6][7][8][9] Currently, platinum based materials have been reported as the most efficient HER catalysts, which exhibit very low overpotential and good stability.…”

Porosity‐Engineering of MXene as a Support Material for a Highly Efficient Electrocatalyst toward Overall Water Splitting

“…However, its half reactions, especially the anodic oxygen evolution reaction (OER), suffer from sluggish electron‐transfer kinetics that lead to low‐efficiency energy conversion . Precious‐metal‐based electrocatalysts exhibit the highest catalytic activity to reduce the overpotential requirement, but the high cost, scarcity and low stability of these catalysts have hindered their widespread application greatly . Therefore, substantial efforts have been devoted to develop highly efficient and inexpensive materials by reducing the noble metal usage or by exploring viable alternatives .…”

“…Noble metals such as Ir, Ru and Pt and their alloys have been demonstrated to be the best metal catalysts for the OER and/or the HER and overall water electrolysis . However, these catalysts have still not reached the necessary performance.…”

“…[1][2][3][4][5] Precious-metal-based electrocatalysts exhibit the highest catalytic activity to reduce the overpotential requirement, but the high cost, scarcity and low stabilityo ft hesec atalysts have hindered their widespread application greatly. [6][7][8][9][10][11][12] Therefore, substantial efforts have been devotedt od evelop highly efficient and inexpensive materials by reducing the noblem etal usage or by exploring viable alternatives. [7,8,[13][14][15][16][17][18][19][20] There are two common approaches to enhance the activity of an electrocatalyst: ( 1) by increasing the quality of each active site (e.g.,n ormally by modulating the electronic configuration) and (2) by increasing the number of active sites at as pecific mass loading and electrode area (e.g., by engineering the structure and morphology to expose more active sites).…”