Muhammad Qureshi

Bio: Muhammad Qureshi is an academic researcher from King Abdullah University of Science and Technology. The author has contributed to research in topics: Photocatalysis & Water splitting. The author has an hindex of 9, co-authored 13 publications receiving 527 citations. Previous affiliations of Muhammad Qureshi include SLAC National Accelerator Laboratory & Harbin Institute of Technology.

Insights on Measuring and Reporting Heterogeneous Photocatalysis: Efficiency Definitions and Setup Examples

Abstract: Heterogeneous photocatalysis is a potentially competitive solution for the direct production of solar fuels. This research field has seen tremendous growth over the last five decades, and with such an exciting research topic, it has seen—and will continue to see—an increasing number of papers being published in a variety of journals. However, it is becoming increasingly difficult to compare the efficiencies of heterogeneous photocatalyst powders, because different researchers report their results in different ways. Efforts have been made to create standards for reporting data in this field, but there continues to be a discrepancy in published works. This article intends to clarify efficiency definitions, and clarify misconceptions as to why researchers should avoid reporting rates of evolution per gram, per surface area of catalyst, or as turnover frequencies (TOFs) alone, to be able to compare photocatalytic efficiency among different materials. By providing an example of a photoreactor for water splitti...

Temperature Dependence of Electrocatalytic and Photocatalytic Oxygen Evolution Reaction Rates Using NiFe Oxide

Abstract: The present work compares the oxygen evolution reaction (OER) in electrocatalysis and photocatalysis in aqueous solutions using nanostructured NiFeOx as catalysts. The impacts of pH and reaction temperature on the electrocatalytic and photocatalytic OER kinetics were investigated. For electrocatalysis, a NiFeOx catalyst was hydrothermally decorated on Ni foam. In 1 M KOH solution, the NiFeOx electrocatalyst achieved 10 mA cm–2 at an overpotential of 260 mV. The same catalyst was decorated on the surface of Ta3N5 photocatalyst powder. The reaction was conducted in the presence of 0.1 M Na2S2O8 as a strong electron scavenger, thus likely leading to the OER being kinetically relevant. When compared with the bare Ta3N5, NiFeOx/Ta3N5 demonstrated a 5-fold improvement in photocatalytic activity in the OER under visible light irradiation, achieving a quantum efficiency of 24% at 480 nm. Under the conditions investigated, a strong correlation between the electrocatalytic and photocatalytic performances was identi...

An Oxygen-Insensitive Hydrogen Evolution Catalyst Coated by a Molybdenum-Based Layer for Overall Water Splitting

Abstract: For overall water-splitting systems, it is essential to establish O2-insensitive cathodes that allow cogeneration of H2 and O2. An acid-tolerant electrocatalyst is described, which employs a Mo-coating on a metal surface to achieve selective H2 evolution in the presence of O2. In operando X-ray absorption spectroscopy identified reduced Pt covered with an amorphous molybdenum oxyhydroxide hydrate with a local structural order composed of polyanionic trimeric units of molybdenum(IV). The Mo layer likely hinders O2 gas permeation, impeding contact with active Pt. Photocatalytic overall water splitting proceeded using MoOx/Pt/SrTiO3 with inhibited water formation from H2 and O2, which is the prevailing back reaction on the bare Pt/SrTiO3 photocatalyst. The Mo coating was stable in acidic media for multiple hours of overall water splitting by membraneless electrolysis and photocatalysis.

Recent developments in heterogeneous photocatalysts for solar-driven overall water splitting

Abstract: Overall water splitting based on particulate photocatalysts is an easily constructed and cost-effective technology for the conversion of abundant solar energy into clean and renewable hydrogen energy on a large scale. This promising technology can be achieved in a one-step excitation system using a single photocatalyst or via a Z-scheme process based on a pair of photocatalysts. Ideally, such photocatalysis will proceed with charge separation and transport unaffected by recombination and trapping, and surface catalytic processes will not involve undesirable reactions. This review summarizes the basics of overall water splitting via both one-step excitation and Z-scheme processes, with a focus on standard methods of determining photocatalytic performance. Various surface engineering strategies applied to photocatalysts, such as cocatalyst loading, surface morphology control, surface modification and surface phase junctions, have been developed to allow efficient one-step excitation overall water splitting. In addition, numerous visible-light-responsive photocatalysts have been successfully utilized as H2-evolution or O2-evolution photocatalysts in Z-scheme overall water splitting. Prototype particulate immobilization systems with photocatalytic performances comparable to or drastically higher than those of particle suspension systems suggest the exciting possibility of the large-scale production of low-cost renewable solar hydrogen.

Particulate Photocatalysts for Light-Driven Water Splitting: Mechanisms, Challenges, and Design Strategies

Abstract: Solar-driven water splitting provides a leading approach to store the abundant yet intermittent solar energy and produce hydrogen as a clean and sustainable energy carrier. A straightforward route to light-driven water splitting is to apply self-supported particulate photocatalysts, which is expected to allow solar hydrogen to be competitive with fossil-fuel-derived hydrogen on a levelized cost basis. More importantly, the powder-based systems can lend themselves to making functional panels on a large scale while retaining the intrinsic activity of the photocatalyst. However, all attempts to generate hydrogen via powder-based solar water-splitting systems to date have unfortunately fallen short of the efficiency values required for practical applications. Photocatalysis on photocatalyst particles involves three sequential steps: (i) absorption of photons with higher energies than the bandgap of the photocatalysts, leading to the excitation of electron-hole pairs in the particles, (ii) charge separation and migration of these photoexcited carriers, and (iii) surface chemical reactions based on these carriers. In this review, we focus on the challenges of each step and summarize material design strategies to overcome the obstacles and limitations. This review illustrates that it is possible to employ the fundamental principles underlying photosynthesis and the tools of chemical and materials science to design and prepare photocatalysts for overall water splitting.

Particulate photocatalysts for overall water splitting

Abstract: Overall water splitting using powdered photocatalysts is a promising approach to large-scale solar hydrogen production. This Review details recent developments in particulate photocatalysts for overall water splitting based on one- and two-step photoexcitation systems.

Reaction systems for solar hydrogen production via water splitting with particulate semiconductor photocatalysts

Abstract: Photocatalytic water splitting using particulate semiconductor materials has been studied as a simple means of hydrogen production. However, there are still many obstacles to the development of complete, practical and renewable solar hydrogen production processes. This review discusses particulate photocatalyst systems intended for large-scale solar hydrogen production via water splitting, focusing on their current status and potential impact. The cost and efficiency targets for solar-to-fuel conversion on a practical scale are also reviewed, based on the maximum allowable cost of solar hydrogen production systems, which has been estimated to be US$102 m–2, at most. Particulate photocatalyst material design principles are discussed, using efficient oxide photocatalysts as examples. Approaches to constructing photocatalytic reactors extensible to large areas are also introduced. Finally, challenges related to the development of efficient and inexpensive photocatalyst systems and potentially useful analytical methods are outlined. Photocatalytic water splitting with particulate semiconductors represents a promising strategy for the generation of hydrogen as a solar fuel. This review covers recent advances in the development of reaction systems and photocatalysts towards the scale-up of this technology, emphasizing at the same time the challenges to overcome.

Metal–Organic Frameworks in Heterogeneous Catalysis: Recent Progress, New Trends, and Future Perspectives

Abstract: More than 95% (in volume) of all of today’s chemical products are manufactured through catalytic processes, making research into more efficient catalytic materials a thrilling and very dynamic rese...