Steering Cu-Based CO₂RR Electrocatalysts’ Selectivity: Effect of Hydroxyapatite Acid/Base Moieties in Promoting Formate Production

Abstract

Among all CO2 reduction reaction (CO2RR) active metals, copper is the only one which exhibits optimal *CO binding energy for multiple electron transfers. Despite such a unique feature, the use of Cubased CO2RR catalysts at the industrial scale is hampered by large overpotentials and poor selectivity. In this realm, the introduction of acid/basic functionalities at the catalyst surface may help to both overcome scaling relations (i.e. lower CO2RR overpotential) and tune the selectivity of Cu-based catalysts. Herein, we demonstrate that an amphoteric calcium phosphate additive (Hydroxyapatite, HAP, Ca10(PO4)6(OH)2) alters the product distribution from Cu-based catalysts by steering CO2RR selectivity towards liquid oxygenated products, promoting formate production over CO. 14. Similarly, Sun et al. observed major increases in FEC2H4 when supporting 7 nm Cu nanoparticles onto Ndoped graphene instead of carbon black (ca. 79% vs 6.3%, E = -1.1 V vs RHE) 15 , while an outstanding performance was delivered by Cu nanoparticles on N-doped carbon nanospikes, reaching a remarkable FE ≈ 63% towards ethanol at -1.2 V vs RHE 16 . Both authors attributed such improved selectivity towards

Biochar based cathode enriched with hydroxyapatite and Cu nanoparticles boosting electromethanogenesis

“…Small increases in pH were noted for the systems with HAP, as they remained more stable during the test, thermodynamically favouring methane production [2,72]. Such an optimal control of pH might be ascribed to the peculiar interface behaviour of HAP [47]. Indeed, when in contact with water, hydroxyapatite generates disordered hydrated layers located at the surface and undergoes partial dissolution with the release of its constituting ions (calcium cations, phosphates, and hydroxyl ions).…”

Applications of Rare Earth Promoted Transition Metal Sulfides in Electrocatalysis†

“…[ 123 ] It can not only solve the waste of new energy due to intermittent problems, but also alleviate the environmental problems caused by greenhouse gas CO 2 and obtain high value‐ added hydrocarbons. [ 115,117,122,124‐126 ] The core of CO 2 electroreduction technology is the CO 2 reduction reaction (CO 2 RR) at the cathode, that is, water and CO 2 are used as raw materials to convert and obtain carbon monoxide, methane, formic acid, methanol, ethylene, ethanol, acetic acid and other products under reduction potential. However, Co has a highly stable chemical structure and is not prone to chemical reaction.…”

Self-Supporting Metal-Organic Framework-Based Nanoarrays for Electrocatalysis

“…9,10 Besides, electrochemical carbon dioxide reduction reaction (CO 2 RR) shows low Faraday efficiency (FE) and poor product selectivity due to competitive HER and complex proton-coupled multistep reaction process. 11,12 The slow kinetics of methanol oxidation reaction (MOR) also limits the commercialization of direct methanol fuel cells. 13,14 Therefore, rational exploration and design of electrocatalysts with excellent activity, selectivity, and long-term durability are the keys to the development of electrocatalytic energy conversion technology.…”

“…To meet the rapidly growing global energy demand and ease the heavy reliance on nonrenewable fossil fuels, enormous efforts have been made to develop and improve clean renewable energy storage and conversion technologies. , Specifically, electrochemical energy conversion between electricity and chemicals by electrocatalysis is a promising key technology, which can realize the efficient utilization of intermittent renewable energy and provide basic raw materials and fuels for the chemical industry. , However, electrocatalysis still has many bottlenecks that seriously hinder its practical applications. For example, oxygen evolution reaction (OER) involving multiple electron-proton transfers has slower reaction kinetics, which limits the overall efficiency of electrolytic water. , Hydrogen evolution reaction (HER) requires overcoming extra energetic barriers to generate reaction intermediates in alkaline media, and its reaction kinetics is about 3 orders of magnitude lower than those in acidic media. , Oxygen reduction reaction (ORR) is an important cathodic reaction in fuel cells, but its slow kinetic process significantly limits the large-scale application. , Besides, electrochemical carbon dioxide reduction reaction (CO 2 RR) shows low Faraday efficiency (FE) and poor product selectivity due to competitive HER and complex proton-coupled multistep reaction process. , The slow kinetics of methanol oxidation reaction (MOR) also limits the commercialization of direct methanol fuel cells. , Therefore, rational exploration and design of electrocatalysts with excellent activity, selectivity, and long-term durability are the keys to the development of electrocatalytic energy conversion technology.…”