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Switching to renewable, carbon-neutral sources of energy is urgent and critical for climate change mitigation. Despite how hydrogen production by electrolyzing water can enable renewable energy storage, current technologies unfortunately require rare and expensive platinum group metal electrocatalysts, which limit their economic viability. Transition metal dichalcogenides (TMDs) are low-cost, earth-abundant materials that possess the potential to replace platinum as the hydrogen evolution catalyst for water electrolysis, but so far, pristine TMDs are plagued by poor catalytic performances. Defect engineering is an attractive approach to enhance the catalytic efficiency of TMDs and is not subjected to the limitations of other approaches like phase engineering and surface structure engineering. In this minireview, we discuss the recent progress made in defect-engineered TMDs as efficient, robust, and low-cost catalysts for water splitting. The roles of chalcogen atomic defects in engineering TMDs for improvements to the hydrogen evolution reaction (HER) are summarized. Finally, we highlight our perspectives on the challenges and opportunities of defect engineering in TMDs for electrocatalytic water splitting. We hope to provide inspirations for designing the state-of-the-art catalysts for future breakthroughs in the electrocatalytic HER. Agency for Science, Technology and Research (A*STAR) Ministry of Education (MOE) National Research Foundation (NRF) Published version X.Y.K. acknowledges that this research is funded by the Singapore National Academy of Science (SNAS) and the National Research Foundation (NRF) of Singapore under the SNAS ASEAN Fellowship Program (NRF-MP-2020-0001). H.S.S. acknowledges that this project is supported by A*STAR under the AME IRG grant no. A2083c0050. H.S.S. is also grateful for the Singapore Ministry of Education Academic Research Fund Tier 1 grants RT 05/19 and RG 09/22, and the NTU 5th ACE Grant Call. S.-P.C. thanked the Ministry of Higher Education (MOHE) Malaysia for supporting this work under the Malaysia Research University Network (MRUN) (Project No. 304/PJKIMIA/656501/829 K145).

Photocatalysis is a perennial solution that promises to resolve deep-rooted challenges related to environmental pollution and energy deficit through harvesting the inexhaustible and renewable solar energy. To date, a cornucopia of photocatalytic materials has been investigated with the research wave presently steered by the development of novel, affordable, and effective metal-free semiconductors with fascinating physicochemical and semiconducting characteristics. Coincidentally, the recently emerged red phosphorus (RP) semiconductor finds itself fitting perfectly into this category ascribed to its earth abundant, low-cost, and metal-free nature. More notably, the renowned red allotrope of the phosphorus family is spectacularly bestowed with strengthened optical absorption features, propitious electronic band configuration, and ease of functionalization and modification as well as high stability. Comprehensively detailing RP's roles and implications in photocatalysis, this review article will first include information on different RP allotropes and their chemical structures, followed by the meticulous scrutiny of their physicochemical and semiconducting properties such as electronic band structure, optical absorption features, and charge carrier dynamics. Besides that, state-of-the-art synthesis strategies for developing various RP allotropes and RP-based photocatalytic systems will also be outlined. In addition, modification or functionalization of RP with other semiconductors for promoting effective photocatalytic applications will be discussed to assess its versatility and feasibility as a high-performing photocatalytic system. Lastly, the challenges facing RP photocatalysts and future research directions will be included to propel the feasible development of RP-based systems with considerably augmented photocatalytic efficiency. This review article aspires to facilitate the rational development of multifunctional RP-based photocatalytic systems by widening the cognizance of rational engineering as well as to fine-tune the electronic, optical, and charge carrier properties of RP.

The interactions of CO2 with terrace, step, and defect or kink sites on Pt surfaces were investigated using temperature-programmed desorption, X-ray photoelectron spectroscopy, and density function...

The photocatalytic conversion of CO2 to energy-rich CH4 solar fuel is an ideal strategy for future energy generation as it can resolve global warming and the imminent energy crisis concurrently. Ho...

Palm shell derived activated carbon was utilized as a potential adsorbent to remove rhodamine B (RB) from aqueous solution. Activated carbon was prepared from palm shell through a physiochemical activation process to yield a sample with a Brunauer−Emmett−Teller (BET) surface area of 476.8 m2·g−1. The ability of the prepared activated carbon for dye adsorption was examined in a series of batch experiments. The effect of various process parameters such as initial dye concentration [(41.8 to 208.8) μmol·L−1], solution pH (3 to 11), and temperature [(30 to 50) °C] on the adsorption capacity of the adsorbent was investigated. Various adsorption isotherms (Langmuir, Freundlich, and Temkin) were used to interpret the experimental data. The obtained sorption data were reasonably described by the Langmuir model. The Temkin isotherm confirmed the presence of a repulsive lateral interaction in the adsorbent surface. Pseudofirst- and second-order kinetic models were used to predict the kinetics of the adsorption proc...

Combined photolysis and predominantly photocatalytic degradation of phenol under UV-C light (λ = 254 nm) with the maximum intensity of 5400 μW/cm2 was carried out in a batch reactor. The TiO2 photocatalysts were supported on glass beads, silica gel, and quartz sand using a sol−gel method. The supported TiO2 catalysts were characterized by XRD, SEM, and EDX analyses. Factors affecting the photocatalytic degradation of phenol such as pH, oxygen supply rate, initial phenol concentration, and H2O2 concentration were investigated. TiO2 supported on quartz sand gave the highest efficiency with 90% degradation of 50 mg/L phenol solution in 6 h, followed by TiO2 supported on silica gel and glass beads with 86% and 74%, respectively. The higher photoactivity of supported TiO2 on quartz sand was ascribed to the high crystallinity and high quantity of Ti, and the absence of ions which could inhibit the crystallization on the catalyst surface. The supported TiO2 was found to be stable for repeated use. The results su...

Composite catalysts composed of microporous HZSM-5 and mesoporous MCM-41/SBA-15 molecular sieve materials were synthesized using the seeding method. The mesoporous materials containing pure silica ...

Catalytic cracking of palm-oil-based fatty acids mixtures (FAM) and used palm oil (UPO) was performed over composite catalysts (HZSM-5 and MCM-41/ZSM-5). The reaction was studied in the temperature range of 673−723 K and a weight hourly space velocity of WHSV = 2.5−4.5 h-1 in a fixed-bed microreactor. A lumped parameter model was proposed to represent the catalytic cracking kinetics of FAM and UPO. The sequential strategy was used to estimate the lumped kinetic constants for three-, four- and six-lump models. The role of the catalyst in the product distribution was determined from the kinetic model that was proposed. The conversion and yield of different products predicted by the six-lump model showed good agreement with the experimental data.

The decomposition of methane into carbon and hydrogen over 15 mol % MnOx/20 mol %NiO/TiO2 catalysts was investigated. The effects of catalyst synthesis and pretreatment of 15 mol % MnOx/20 mol % Ni...

Experiments were conducted in a fixed-bed catalytic reactor to study the decomposition of methane to hydrogen and carbon over 13 wt % Ni/TiO2-based catalyst. The variables include the volumetric fl...