Porous high-entropy alloys as efficient electrocatalysts for water-splitting reactions

Porous high-entropy alloys (HEAs) have emerged as promising electrocatalysts for water-splitting reactions, owing to their rich dissimilar active sites, elemental diversity, and multiple functionalities. The rational design of HEAs for water-splitting attracted great interest in improving their current performance, so it is essential to provide timely updates on this field. This review emphasizes the preparation methods of porous HEAs and the effect of their salient features like high configurational entropy, cocktail effect, lattice distortion, and sluggish diffusion on oxygen evolution reaction (OER) and hydrogen evolution reaction (HER). This mini-review also provides some insights into the current limitations and future perspectives to direct research on the development of ideal HEAs for OER and HER

Electrochemical Immunosensor for Ultra-Low Detection of Human Papillomavirus Biomarker for Cervical Cancer

Human papillomavirus (HPV) is the causative agent for cervical cancer. Of the various types of HPV, the high-risk HPV-16 type is the most important antigenic high-risk HPV. In this work, the antigenic HPV-16 L1 peptide was immobilized on a glassy carbon electrode and used to detect several concentrations of the anti-HPV-16 L1 antibody, and vice versa. Two electrode platforms were used: onion-like carbon (OLC) and its polyacrylonitrile (OLC-PAN) composites. Both platforms gave a wide linear concentration range (1.95 fg/mL to 6.25 ng/mL), excellent sensitivity (>5.2 μA/log ([HPV-16 L1, fg/mL]), and extra-ordinarily low limit of detection (LoD) of 1.83 fg/mL (32.7 aM) and 0.61 fg/mL (10.9 aM) for OLC-PAN and OLC-based immunosensors, respectively. OLC-PAN modified with the HPV-16 L1 protein showed low LoD for the HPV-16 L1 antibody (2.54 fg/mL, i.e., 45.36 aM), proving its potential use for screening purposes. The specificity of detection was proven with the anti-ovalbumin antibody (anti-OVA) and native ovalbumin protein (OVA). An immobilized antigenic HPV-16 L1 peptide showed insignificant interaction with anti-OVA in contrast with the excellent interaction with anti-HPV-16 L1 antibody, thus proving high specificity. The application of the immunosensor as a potential point-of-care (PoC) diagnostic device was investigated with screen-printed carbon electrodes, which detected ultra-low (ca. 0.7 fg/mL ≈ 12.5 aM) and high (ca. 12 μg/mL ≈ 0.21 μM) concentrations. This study represents the lowest LoD reported for HPV-16 L1. It opens the door for further investigation with other electrode platforms and realization of PoC diagnostic devices for screening and testing of HPV biomarkers for cervical cancer

Efforts at Enhancing Bifunctional Electrocatalysis and Related Events for Rechargeable Zinc-Air Batteries

Invited for this month's cover picture is the group of Prof. Dr. Kenneth I. Ozoemena at the University of the Witwatersrand and collaborators from Qatar University and Peking University. The Front Cover illustrates the significance of bifunctional electrocatalysis (ORR / OER) and zinc anode as the key drivers for the development of rechargeable zinc-air batteries that promise to revolutionize electricity storage and applications (represented herein as electric vehicle charging point). Read the full text of the Review at 10.1002/celc.202100574

Pd nanocrystals encapsulated in MOF-derived Ni/N-doped hollow carbon nanosheets for efficient thermal CO oxidation: unveiling the effect of porosity

Rational synthesis of Ni-metal-organic-framework (MOF)-derived hollow N-doped carbon (Ni-MOF-HNC) nanostructures has garnered great attention in various catalytic reactions due to their outstanding catalytic and physicochemical merits, but their activity toward thermal CO oxidation (COOxid) is not emphasized enough. Herein, we tailored the fabrication of Ni-MOF-HNC encapsulated Pd nanocrystals (Pd/Ni-MOF-HNC) for efficient COOxid at low temperature, driven by microwave-irradiation, annealing at 900 °C and chemical etching to form Ni-MOF-HNC that is used as a support for the growth of Pd nanocrystals under microwave-irradiation. The obtained Pd/Ni-MOF-HNC possesses hollow carbon sheets with a great surface area (153.05 m2 g−1), pore volume (0.12 cm3 g−1), rich Pd/Ni-Nx active sites, Ni-metal defects, rich N-content (7.53 at%), mixed Pd/Ni-oxide phases, and uniformly distributed ultra-small Pd nanocrystals (7.03 ± 1.10 nm); meanwhile, Pd/Ni-MOF-NC formed without etching had no porosity and less Ni-metal defects. The thermal COOxid activity of Pd/Ni-MOF-HNC was significantly superior to Pd/Ni-MOF-NC and commercial Pd/C catalysts. This is evidenced in the great ability of Pd/Ni-MOF-HNC to utterly oxidize CO at a lower complete conversion temperature (T100) of 114.5 °C compared with Pd/Ni-MOF-NC (153.8 °C) and Pd/C (201.5 °C) under atmospheric pressure. Conspicuously, the T100 of Pd/Ni-MOF-HNC was lower than those of most previously reported Pd-based catalysts due to the high porosity, surface area, and electronic interaction of Pd/Ni-Nx, and Ni-metal defects, which promote the adsorption/activation of reactants (CO + O2), decrease the activation energy to 73.1 kJ mol−1 and enhance the reaction rate at the same CO conversion percentage. Thus, this study may open the gates for the utilization of MOF-HNC as a support for Pd-based catalysts for thermal COOxidThis work was supported by the Qatar University High Impact Internal Grant (QUHI-CAM-22/23-550), the Qatar National Research Funds (NPRP13S-0117-200095 and NPRP12S-0228-190182), and the NRF/DSI/Wits SARChi Chair in Materials Electrochemistry and Energy Technologies (MEET) (UID No. 132739)

Ternary PdNiO nanocrystals-ornamented porous CeO2/onion-like carbon for electrooxidation of carbon monoxide: unveiling the effect of supports and electrolytes

Porous ternary Pd-based catalysts are highly promising for various electrocatalytic applications, due to their low Pd mass, high surface area, accessible active sites, and tunable electronic structure; however, their activity for CO oxidation (COoxid) in different electrolytes is yet to be reported. Herein, ternary PdNiO nanocrystals supported on porous CeO2/onion-like carbon nanostructures (PdNiO-CeO2/OLC) were prepared by the sol-gel and impregnation approaches for electrochemical COoxid in different electrolytes at room temperature. Notably, porous CeO2/OLC acts as a support and nanoreactor for supporting the growth of PdNiO without the need for reducing agents or surfactants. The as-obtained PdNiO-CeO2/OLC had a porous sponge-like structure composed of ultra-small PdNiO nanocrystals (8 ± 1 nm) distributed on porous flower-like CeO2 and OLC, which possessed unique merits of multifunctional structure, clean surface, low mass of Pd (10 wt%), porosity (0.30 cm3 g−1), and high surface area (155.66 m2 g−1). The COoxid activity of PdNiO-CeO2/OLC was higher than those of PdNiO/OLC, PdNiO-CeO2, and commercial Pd/C catalyst, owing to the electronic interaction of PdNiO with CeO2/OLC support, which eases CO adsorption/activation alongside activation/dissociation of H2O to generate active oxygenated species (i.e., OH) needed for accelerating COoxid kinetics. The COoxid activity of PdNiO-CeO2/OLC in acidic electrolyte (HClO4) was better than those in alkaline (KOH) and neutral (NaHCO3) electrolytes. This study may open new doorways for understanding the effect of electrolytes and supports on the COoxid activity of porous ternary Pd-based catalysts.This work was supported by Qatar University High Impact Internal Grant (QUHI-CAM-22/23-550), Qatar National Research Fund (NPRP13S-0117-200095), and NRF/DSI/Wits SARChI Chair in Materials Electrochemistry and Energy Technologies (MEET) (UID No. 132739)

Efforts at Enhancing Bifunctional Electrocatalysis and Related Events for Rechargeable Zinc-Air Batteries

Rechargeable zinc-air batteries (RZABs) are one of the most promising next-generation energy-storage technologies for stationary applications (home and industry), wearable and portable electronics, and transportation (including electric vehicles) due to their high energy density, environmental friendliness, safety, and low cost. However, RZABs still face serious challenges (such as sluggish oxygen reactions, poor durability, inferior reversibility of the zinc anode, and low cell energy efficiency) that conspire against their widespread commercialization. The reactions that occur at the three key components of the RZAB (air cathode, zinc anode, and electrolyte) co-operatively conspire against its performance. Thus, this review focuses on the bifunctional electrocatalytic events at the cathode (i. e., oxygen reduction reaction (ORR) and oxygen evolution reaction (OER)). That is in addition to the recent developments aimed at mitigating the performance-limiting events at the anode and the electrolytes. This review directs the attention of researchers and users to the critical areas for the development of the next-generation RZABs

Efforts at Enhancing Bifunctional Electrocatalysis and Related Events for Rechargeable Zinc‐Air Batteries

Rechargeable zinc-air batteries (RZABs) are one of the most promising next-generation energy-storage technologies for stationary applications (home and industry), wearable and portable electronics, and transportation (including electric vehicles) due to their high energy density, environmental friendliness, safety, and low cost. However, RZABs still face serious challenges (such as sluggish oxygen reactions, poor durability, inferior reversibility of the zinc anode, and low cell energy efficiency) that conspire against their widespread commercialization. The reactions that occur at the three key components of the RZAB (air cathode, zinc anode, and electrolyte) co-operatively conspire against its performance. Thus, this review focuses on the bifunctional electrocatalytic events at the cathode (i. e., oxygen reduction reaction (ORR) and oxygen evolution reaction (OER)). That is in addition to the recent developments aimed at mitigating the performance-limiting events at the anode and the electrolytes. This review directs the attention of researchers and users to the critical areas for the development of the next-generation RZABs