Carbon‐based metal‐free catalysts for electrochemical CO 2 reduction: Activity, selectivity, and stability (original) (raw)
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Nanotechnology, 2017
Electrochemical CO reduction (ECR) offers an important pathway for renewable energy storage and fuels production. It still remains a challenge in designing highly selective, energy-efficient, robust, and cost-effective electrocatalysts to facilitate this kinetically slow process. Metal-free carbon-based materials have features of low cost, good electrical conductivity, renewability, diverse structure, and tunability in surface chemistry. In particular, surface functionalization of carbon materials, for example by doping with heteroatoms, enables access to unique active site architectures for CO adsorption and activation, leading to interesting catalytic performances in ECR. We aim to provide a comprehensive review of this category of metal-free catalysts for ECR, providing discussions and/or comparisons among different nonmetallic catalysts, and also possible origin of catalytic activity. Fundamentals and some future challenges are also described.
Metal-and Carbon-Based Materials as Heterogeneous Electrocatalysts for CO 2 Reduction
Journal of Nanoscience and Nanotechnology, 2018
Climate change caused by continuous rising level of CO 2 and the depletion of fossil fuels reserves has made it highly desirable to electrochemically convert CO 2 into fuels and commodity chemicals. Implementing this approach will close the carbon cycle by recycling CO 2 providing a sustainable way to store energy in the chemical bonds of portable molecular fuels. In order to make the process commercially viable, the challenge of slow kinetics of CO 2 electroreduction and low energy efficiency of the process need to be addressed. To this end, this review summarizes the progress made in the past few years in the development of heterogeneous electrocatalysts with a focus on nanostructured material for CO 2 reduction to CO, HCOOH/HCOO − , CH 2 O, CH 4 , H 2 C 2 O 4 /HC 2 O − 4 , C 2 H 4 , CH 3 OH, CH 3 CH 2 OH, etc. The electrocatalysts presented here are classified into metals, metal alloys, metal oxides, metal chalcogenides and carbon based materials on the basis of their elemental composition, whose performance is discussed in light of catalyst activity, product selectivity, Faradaic efficiency (FE), catalytic durability and in selected cases mechanism of CO 2 electroreduction. The effect of particle size, morphology and solution-electrolyte type and composition on the catalyst property/activity is also discussed and finally some strategies are proposed for the development of CO 2 electroreduction catalysts. The aim of this article is to review the recent advances in the field of CO 2 electroreduction in order to further facilitate research and development in this area.
High-Performance Electrochemical CO2 Reduction Cells Based on Non-noble Metal Catalysts
ACS Energy Letters
The promise and challenge of electrochemical mitigation of carbon dioxide calls for innovations at the catalyst material level as well as at the reactor level. In this work, enabled by our high-performance and earth-abundant electrocatalyst materials for carbon dioxide reduction reactions, we developed alkaline micro-flow electrolytic cells for energy-efficient, selective, fast and durable carbon dioxide conversion to carbon monoxide and formate. With a cobalt phthalocyanine-based cathode catalyst, the carbon monoxideselective cell starts to operate at a 0.26 V overpotential and reaches a Faradaic efficiency of 94% and a partial current density of 31 mA/cm 2 at a 0.56 V overpotential. With a tin dioxide-based cathode catalyst, the formate-selective cell starts to operate at a 0.76 V overpotential and reaches a Faradaic efficiency of 82% and a partial current density of 113 mA/cm 2 at a 1.36 V overpotential. In contrast to previous studies, we found that the overpotential reduction from using the alkaline electrolyte is mostly contributed by a pH gradient near the cathode surface.
New trends in the development of heterogeneous catalysts for electrochemical CO 2 reduction
Catalysis Today, 2016
The electrochemical conversion of CO 2 into energy-rich fuels and chemicals has gained significant interest as a potential strategy for simultaneously mitigating increasing global CO 2 concentration and effectively storing intermittent renewable energy from sources such as solar and wind. This process recycles CO 2 , permitting a carbon-neutral, closed-loop of fuel combustion and waste CO 2 reduction to help prevent a rising concentration of this greenhouse gas in the atmosphere. At the same time, intermittent electricity generation can be stored in an energy-dense, portable form in chemical bonds. However, the stability of CO 2 makes its conversion kinetically challenging, generally requiring a large overpotential, and thus the efficiency of electrochemical CO 2 reduction is strongly dependent on the activity and selectivity of the cathodic electrocatalyst. In this review, we discuss the current state-of-the-art of unconventional heterogeneous catalysts with a focus on activity and product selectivity, even if the CO 2 reduction reaction mechanism remains uncertain. Various emerging approaches to enhance the yield of specific products and the overall rate of reaction will also be addressed. Finally, prospects for the development of nextgeneration catalysts will be discussed.
Catalysis Today, 2014
In this review article, we report the development and utilisation of fuel cells, metal electrodes in aqueous electrolyte and molecular catalysts in the electrochemical reduction of CO 2. Fuel cells are able to function in both electrolyser and fuel cell mode and could potentially reduce CO 2 and produce energy at the same time. However, it requires considerably high temperatures for efficient operation. Direct reduction using metal electrodes and molecular catalysts are possible at room temperatures but require an additional applied potential and generally have low current densities. Density functional theory (DFT) studies have been used and have begun to unveil possible mechanisms involved which could lead to improvements and development of more efficient catalysts.
Nanomaterials
Electrochemical CO2 reduction reaction (CO2RR) provides a promising approach to curbing harmful emissions contributing to global warming. However, several challenges hinder the commercialization of this technology, including high overpotentials, electrode instability, and low Faradic efficiencies of desirable products. Several materials have been developed to overcome these challenges. This mini-review discusses the recent performance of various cobalt (Co) electrocatalysts, including Co-single atom, Co-multi metals, Co-complexes, Co-based metal–organic frameworks (MOFs), Co-based covalent organic frameworks (COFs), Co-nitrides, and Co-oxides. These materials are reviewed with respect to their stability of facilitating CO2 conversion to valuable products, and a summary of the current literature is highlighted, along with future perspectives for the development of efficient CO2RR.
Literature Survey on Electrochemical Reduction of CO
2014
The electrochemical reduction of carbon dioxide has been studied for a number of years and several good reviews have been written on the subject as well as papers investigating the reaction mechanisms for CO2 reduction. Most of the focus has been investigating different products that can be formed using various catalysts with the majority of the work being done on metal electrodes in either aqueous or organic media. The main products of CO2 reduction are methane, ethylene, formate (formic acid), carbon monoxide and some alcohols (methanol, ethanol, propanol). Since hydrogen evolution is a competing reaction, metals with high overpotential for hydrogen evolution, such as Hg, In , Pb, Cd, have higher efficiencies for CO2 reduction. Because of their aprotic nature, organic electrolytes also help suppress hydrogen evolution in addition to having higher solubility of CO2. Furthermore, several researchers have found that lower temperatures suppress hydrogen evolution and increase efficien...
CO 2 reduction: the quest for electrocatalytic materials
Rising levels of carbon dioxide (CO 2) are of significant concern in modern society, as they lead to global warming and consequential environmental and societal changes. It is of importance to develop industries with a zero or negative CO 2 footprint. Electrochemistry, where one of the reagents is electrons, is an environmentally clean technology that is capable of addressing the conversion of CO 2 to value-added products. The key factor in the process is the use of catalytic electrode materials that lead to the desired reaction and product. Significant progress in this field has been achieved in the past two years. This review discusses the progress in the development of electrocatalysts for CO 2 reduction achieved during this time period.