Ambient Electrosynthesis toward Single‐Atom Sites for Electrocatalytic Green Hydrogen Cycling

Abstract

With the ultimate atomic utilization, well‐defined configuration of active sites and unique electronic properties, catalysts with single‐atom sites (SASs) exhibit appealing performance for electrocatalytic green hydrogen generation from water splitting and further utilization via hydrogen–oxygen fuel cells, such that a vast majority of synthetic strategies toward SAS‐based catalysts (SASCs) are exploited. In particular, room‐temperature electrosynthesis under atmospheric pressure offers a novel, safe, and effective route to access SASs. Herein, the recent progress in ambient electrosynthesis toward SASs for electrocatalytic sustainable hydrogen generation and utilization, and future opportunities are discussed. A systematic summary is started on three kinds of ambient electrochemically synthetic routes for SASs, including electrochemical etching (ECE), direct electrodeposition (DED), and electrochemical leaching–redeposition (ELR), associated with advanced characterization techniques. Next, their electrocatalytic applications for hydrogen energy conversion including hydrogen evolution reaction, oxygen evolution reaction, overall water splitting, and oxygen reduction reaction are reviewed. Finally, a brief conclusion and remarks on future challenges regarding further development of ambient electrosynthesis of high‐performance and cost‐effective SASCs for many other electrocatalytic applications are presented.

Precise control of the catalyst interface at the atomic level

“…58–60 If the hydrogen/oxygen generated by electrolysis at the electrode/catalyst interface cannot be removed quickly, it will occupy the active sites of the reaction, thus reducing the reaction efficiency. 61–63 An excellent catalyst should have appropriate adsorption energy for reaction intermediates on the surface of materials ( i.e. , neither too strong nor too weak).…”

“…[58][59][60] If the hydrogen/oxygen generated by electrolysis at the electrode/catalyst interface cannot be removed quickly, it will occupy the active sites of the reaction, thus reducing the reaction efficiency. [61][62][63] An excellent catalyst should have appropriate adsorption energy for reaction intermediates on the surface of materials (i.e., neither too strong nor too weak). 14,[64][65][66] Therefore, accurate optimization of the adsorption/desorption behavior of intermediates on the surface of materials is the key to improve the catalytic performance.…”

Dynamic Electrodeposition on Bubbles: An Effective Strategy toward Porous Electrocatalysts for Green Hydrogen Cycling

“…The energy crisis and environmental pollution due to excessive depletion of nonrenewable fossil fuels accelerate the exploration of sustainable energy sources. , In response, a new energy paradigm based on green hydrogen cycling has been proposed as a promising alternative to the current fossil fuel-based hydrocarbon economy . As shown in Figure , renewable energy resources, such as solar, wind, and hydropower, can be harvested to drive water splitting to produce H 2 , which can be further stored and used as an energy carrier to release electric energy via H 2 –O 2 fuel cells with no greenhouse gas emission. , The generation and utilization of H 2 involve four half-reactions including hydrogen evolution reaction (HER), oxygen evolution reaction (OER), hydrogen oxidation reaction (HOR), and oxygen reduction reaction (ORR). Their sluggish kinetics usually result in low efficiency .…”

Negatively Charging Nonprecious Metal Phosphides/Selenides via General Polyaniline Coating for Improved Alkaline H2 Evolution

“…In view of the interface reaction properties of the HER, engineering the electrocatalyst/electrolyte interface to modulate the corresponding electronic structure would result in improved electrocatalytic performance. − For example, our group previously modified the surfaces of diverse transition metals by nitrogen atoms through high temperature ammonium carbonate annealing. Because of the critical electrostatic interaction between surface electron-rich nitrogen atoms with polar water molecules (electron-deficient hydrogen atoms/electron-rich hydroxide), neutral water can be destabilized for improved hydrogen evolution .…”