Comprehensive understanding and rational regulation of microenvironment for gas‐involving electrochemical reactions

Abstract

Substantial progress has been made in the understanding of gas‐involving electrochemical reactions recently for the sake of clean, renewable, and efficient energy technologies. However, the specific influence mechanism of the microenvironment at the reaction interface on the electrocatalytic performance (activity, selectivity, and durability) remains unclear. Here, we provide a comprehensive understanding of the interfacial microenvironment of gas‐involving electrocatalysis, including carbon dioxide reduction reaction and nitrogen reduction reaction, and classify the factors affecting the reaction thermodynamics and kinetics into gas diffusion, proton supply, and electron transfer. This categorization allows a systematic survey of the literature focusing on electrolyzer‐level (optimization of the device, control of the experimental condition, and design of the working electrode), electrolyte‐level (increase of gas solubility, regulation of proton supply, and substitution of anodic reaction), and electrocatalyst‐level strategies (promotion of gas affinity, adjustment of hydrophobicity, and enhancement of conductivity), aiming to retrieve the correlations between the microenvironment and electrochemical performance. Finally, priorities for future studies are suggested to support the comprehensive improvement of next‐generation gas‐involving electrochemical reactions.

Single‐atom catalysts for the electrochemical reduction of carbon dioxide into hydrocarbons and oxygenates

“…There has been no unifying criterion regarding the stability of catalysts in the literature. However, Spurgeon and Kumar 295 suggested that an electrocatalyst should have a long‐term operational stability of more than 20,000 h to merit commercial viability 295–297 . A catalyst should have a partial current density for a particular product of at least 100 mA cm −2 to qualify for commercial application.…”

“…However, Spurgeon and Kumar 295 suggested that an electrocatalyst should have a long-term operational stability of more than 20,000 h to merit commercial viability. [295][296][297] A catalyst should have a partial current density for a particular product of at least 100 mA cm −2 to qualify for commercial application. Unfortunately, SACs achieved only approximately 10% of the minimum requirement for the current density.…”

Molecular Imprinting Technology Enables Proactive Capture of Nitrogen for Boosted Ammonia Synthesis under Ambient Conditions

“…[22,23] Considering NRR primarily occurs at the multiphase interface among gaseous nitrogen, solid electrocatalyst, and liquid electrolyte, it is better to propose the optimization strategy based on the three-phase reaction interface. [24] Mimicking key aspects of enzymatic catalysis and building microenvironments over solid catalyst surfaces may play a critical advantage in inducing the confinement effect and controlling the transport of the reactants. [25] Molecularly imprinted polymers (MIPs) are a kind of synthetic materials that are able to selectively recognize and grapple target molecules with tailor-made molecular recognition sites.…”

Asymmetric electrode design with built‐in nitrogen transfer channel achieving maximized three‐phase reaction region for electrochemical ammonia synthesis

“…On the other hand, the concentration of proton source should be controlled to be neither too high to inhibit the electron‐stealing hydrogen evolution reaction nor too low since NRR pertains to proton‐coupled electron transfer reaction, and the lack of proton supply will still limit the nitrogen reduction process 20,21 . That is, in addition to the thermodynamics, the dynamics of both nitrogen and proton source should be optimized simultaneously to maximize the three‐phase reaction region and effectively push the NRR forward 22,23 . Unfortunately, the interfacial engineering of the NRR process has received little attention 24,25 .…”

“…20,21 That is, in addition to the thermodynamics, the dynamics of both nitrogen and proton source should be optimized simultaneously to maximize the three-phase reaction region and effectively push the NRR forward. 22,23 Unfortunately, the interfacial engineering of the NRR process has received little attention. 24,25 Conventional working electrode applied in the NRR test is usually unmodified, with the electrocatalyst flooded by the electrolyte, and only the surface material could get access to the nitrogen, which inevitably gives rise to sluggish reaction rate.…”