Advances in Biomimetic Photoelectrocatalytic Reduction of Carbon Dioxide

Leveraging experimental and computational tools for advancing carbon capture adsorbents research

CO2 emissions have been steadily increasing and have been a major contributor for climate change compelling nations to take decisive action fast. The average global temperature could reach 1.5 °C by 2035 which could cause a significant impact on the environment, if the emissions are left unchecked. Several strategies have been explored of which carbon capture is considered the most suitable for faster deployment. Among different carbon capture solutions, adsorption is considered both practical and sustainable for scale-up. But the development of adsorbents that can exhibit satisfactory performance is typically done through the experimental approach. This hit and trial method is costly and time consuming and often success is not guaranteed. Machine learning (ML) and other computational tools offer an alternate to this approach and is accessible to everyone. Often, the research towards materials focuses on maximizing its performance under simulated conditions. The aim of this study is to present a holistic view on progress in material research for carbon capture and the various tools available in this regard. Thus, in this review, we first present a context on the workflow for carbon capture material development before providing various machine learning and computational tools available to support researchers at each stage of the process. The most popular application of ML models is for predicting material performance and recommends that ML approaches can be utilized wherever possible so that experimentations can be focused on the later stages of the research and development.

Drivers and Pathways for the Recovery of Critical Metals from Waste-Printed Circuit Boards

The ever-increasing importance of critical metals (CMs) in modern society underscores their resource security and circularity. Waste-printed circuit boards (WPCBs) are particularly attractive reservoirs of CMs due to their gamut CM embedding and ubiquitous presence. However, the recovery of most CMs is out of reach from current metal-centric recycling industries, resulting in a flood loss of refined CMs. Here, 41 types of such spent CMs are identified. To deliver a higher level of CM sustainability, this work provides an insightful overview of paradigm-shifting pathways for CM recovery from WPCBs that have been developed in recent years. As a crucial starting entropy-decreasing step, various strategies of metal enrichment are compared, and the deployment of artificial intelligence (AI) and hyperspectral sensing is highlighted. Then, tailored metal recycling schemes are presented for the platinum group, rare earth, and refractory metals, with emphasis on greener metallurgical methods contributing to transforming CMs into marketable products. In addition, due to the vital nexus of CMs between the environment and energy sectors, the upcycling of CMs into electro-/photo-chemical catalysts for green fuel synthesis is proposed to extend the recycling chain. Finally, the challenges and outlook on this all-round upgrading of WPCB recycling are outlined.

Engineering of bespoke photosensitiser-microbe interfaces for enhanced semi-artificial photosynthesis

Biohybrid systems for solar fuel production integrate artificial light-harvesting materials with biological catalysts such as microbes. In this perspective, we discuss the rational design of the abiotic-biotic interface in biohybrid systems by reviewing microbes and synthetic light-harvesting materials, as well as presenting various approaches to coupling these two components together. To maximise performance and scalability of such semi-artificial systems, we emphasise that the interfacial design requires consideration of two important aspects: attachment and electron transfer. It is our perspective that rational design of this photosensitiser-microbe interface is required for scalable solar fuel production. The design and assembly of a biohybrid with a well-defined electron transfer pathway allows mechanistic characterisation and optimisation for maximum efficiency. Introduction of additional catalysts to the system can close the redox cycle, omitting the need for sacrificial electron donors. Studies that electronically couple light-harvesters to well-defined biological entities, such as emerging photosensitiser-enzyme hybrids, provide valuable knowledge for the strategic design of whole-cell biohybrids. Exploring the interactions between light-harvesters and redox proteins can guide coupling strategies when translated into larger, more complex microbial systems.

Review on Microreactors for Photo-Electrocatalysis Artificial Photosynthesis Regeneration of Coenzymes

In recent years, with the outbreak of the global energy crisis, renewable solar energy has become a focal point of research. However, the utilization efficiency of natural photosynthesis (NPS) is only about 1%. Inspired by NPS, artificial photosynthesis (APS) was developed and utilized in applications such as the regeneration of coenzymes. APS for coenzyme regeneration can overcome the problem of high energy consumption in comparison to electrocatalytic methods. Microreactors represent a promising technology. Compared with the conventional system, it has the advantages of a large specific surface area, the fast diffusion of small molecules, and high efficiency. Introducing microreactors can lead to more efficient, economical, and environmentally friendly coenzyme regeneration in artificial photosynthesis. This review begins with a brief introduction of APS and microreactors, and then summarizes research on traditional electrocatalytic coenzyme regeneration, as well as photocatalytic and photo-electrocatalysis coenzyme regeneration by APS, all based on microreactors, and compares them with the corresponding conventional system. Finally, it looks forward to the promising prospects of this technology.

Strategies for Enhancing the Photocatalytic and Electrocatalytic Efficiency of Covalent Triazine Frameworks for CO2 Reduction

Converting carbon dioxide (CO2) into fuel and high-value-added chemicals is considered a green and effective way to solve global energy and environmental problems. Covalent triazine frameworks (CTFs) are extensively utilized as an emerging catalyst for photo/electrocatalytic CO2 reduction reaction (CO2RR) recently recognized for their distinctive qualities, including excellent thermal and chemical stability, π-conjugated structure, rich nitrogen content, and a strong affinity for CO2, etc. Nevertheless, single-component CTFs have the problems of accelerated recombination of photoexcited electron-hole pairs and restricted conductivity, which limit their application for photo/electrocatalytic CO2RR. Therefore, emphasis will then summarize the strategies for enhancing the photocatalytic and electrocatalytic efficiency of CTFs for CO2RR in this paper, including atom doping, constructing a heterojunction structure, etc. This review first illustrates the synthesis strategies of CTFs and the advantages of CTFs in the field of photo/electrocatalytic CO2RR. Subsequently, the mechanism of CTF-based materials in photo/electrocatalytic CO2RR is described. Lastly, the challenges and future prospects of CTFs in photo/electrocatalytic CO2RR are addressed, which offers a fresh perspective for the future development of CTFs in photo/electrocatalytic CO2RR.

Bioinspired Hydrophobicity for Enhancing Electrochemical CO2 Reduction

Electrochemical carbon dioxide reduction (CO2 R) is a promising pathway for converting greenhouse gasses into valuable fuels and chemicals using intermittent renewable energy. Enormous efforts have been invested in developing and designing CO2 R electrocatalysts suitable for industrial applications at accelerated reaction rates. The microenvironment, specifically the local CO2 concentration (local [CO2 ]) as well as the water and ion transport at the CO2 -electrolyte-catalyst interface, also significantly impacts the current density, Faradaic efficiency (FE), and operation stability. In nature, hydrophobic surfaces of aquatic arachnids trap appreciable amounts of gases due to the "plastron effect", which could inspire the reliable design of CO2 R catalysts and devices to enrich gaseous CO2 . In this review, starting from the wettability modulation, we summarize CO2 enrichment strategies to enhance CO2 R. To begin, superwettability systems in nature and their inspiration for concentrating CO2 in CO2 R are described and discussed. Moreover, other CO2 enrichment strategies, compatible with the hydrophobicity modulation, are explored from the perspectives of catalysts, electrolytes, and electrolyzers, respectively. Finally, a perspective on the future development of CO2 enrichment strategies is provided. We envision that this review could provide new guidance for further developments of CO2 R toward practical applications.

A light-driven photoelectrochemical sensor for highly selective detection of hydroquinone based on type-II heterojunction formed by carbon nanotubes immobilized in 3D honeycomb CdS/SnS2

The ecological environment and public safety are seriously threatened by the typical phenolic contaminant hydroquinone (HQ). Here, using a straightforward physical mixing technique, we created an n-n heterojunction by uniformly immobilizing cadmium sulfide (CdS) nanoparticles on the surface of a three-dimensionally layered, flower-like structure made of tin sulfide (SnS₂). Then, as photosensitizers, carbon nanotubes (CNTs) were added to the CdS/SnS₂ complex to create a type-II heterostructure of CdS/SnS₂/CNTs with synergistic effects. Subsequently, the detector HQ was bound to the modified photoelectrodes, which was accompanied by the hole oxidation of the bound HQ, leading to a significant increase in the photocurrent signal, thus allowing specific and sensitive detection of HQ. Under optimized detection conditions, the proposed photoelectrochemical sensor shows a wide detection range of 0.2 to 100 μM for HQ with a detection limit as low as 0.1 μM. The high accuracy of the sensor was demonstrated by comparison with the detection results of UV-vis spectrophotometry. In addition, the photoelectrochemical sensor exhibits good reproducibility, stability, selectivity, and specificity, providing a light-driven method to detect HQ.