Oxide-based nanostructures for photocatalytic and electrocatalytic applications

Abstract

Diminishing fossil fuels and global warming issues have forced the scientists to look for alternate sources of energy to cater to the ever increasing demand. Artificial systems are being developed in order to mimic natural photosynthesis and directly harvest and convert solar energy into renewable energy and environmental remediation. Despite significant efforts, it has been not possible to design a single material which has sufficient efficiency, stability and low cost. To integrate the desired characteristics in a single component, heterogeneous photocatalysts are designed with multiple functional components which could combine the advantages of different components to overcome the drawbacks of single component photocatalysts. The present highlight gives a concise overview of heterogeneous catalysts that have been developed and studied in our group and some excellent works of others in recent years. The review focuses on the principles of photocatalytic and electrocatalytic activity followed by the some key examples of oxide based materials. This includes a wide range of structural modification and crystal growth leading to composites, heterostructures, including insulator/semiconductor, semiconductor/semiconductor, and multi-hetero nanostructures and core-shell nanostructures which have been modified in order to improve the performance by increasing the light absorption, promoting the charge separation and transportation, enhancing the redox catalytic activity and intrinsic electrocatalytic properties. The electrochemical processes like hydrogen

Recent Progress in the Development of Semiconductor‐Based Photocatalyst Materials for Applications in Photocatalytic Water Splitting and Degradation of Pollutants

“…If E CB is positioned more negative than the potential and the E VB is also aligned more positive than the potential, then the water molecule can split into H 2 and O 2 under sun light irradiation . The photocatalytic water splitting reactions are a thermodynamically uphill route, which requires an energy of 1.23 eV versus normal hydrogen electrode (NHE) as well as high over potentials due to its nonspontaneous process with a ∆ G ° = 237.2 kJ mol −1 (2.46 eV vs NHE) per H 2 O molecule .…”

“…In electrochemistry, over potential is the potential difference between the potential at which the redox reactions are experimentally determined and the thermodynamically observed reduction potential . The 1.23 eV versus NHE in Equation arises from the corresponding oxidation (Equation ) and reduction (Equation ) of water…”

Bimodal Heterogeneous Functionality in Redox‐Active Conjugated Microporous Polymer toward Electrocatalytic Oxygen Reduction and Photocatalytic Hydrogen Evolution

“…Importantly, the photochemical transformation of sunlight into chemical energy has occurred naturally in green plants for millions of years, and is known as photosynthesis. However, sluggish reaction kinetics and the subsequent use of precious‐metal‐based catalysts to catalyze electrochemical and photochemical reactions are found to be major limitations to employing these processes on a large scale . Several materials such as metal oxides, phosphides, sulfides, chalcogenides, inorganic or organic–inorganic hybrid porous and carbon‐based materials are known in the literature separately as either electrocatalysts or photocatalysts, but purely organic‐based catalysts working as electro‐ or photocatalysts have hardly been explored …”

“…However,s luggish reactionk inetics and the subsequent use of precious-metal-based catalystst oc atalyze electrochemical and photochemical reactions are found to be majorl imitations to employing these processes on al arge scale. [16][17][18][19] Severalm aterials such as metal oxides, phosphides, sulfides, chalcogenides, inorganic or organic-inorganic hybrid porousa nd carbon-based materials are knowni nt he literature separately as either electrocatalysts [4,[20][21][22][23][24][25][26][27][28] or photocatalysts, [14,[29][30][31][32] but purely organic-based catalysts working as electro-or photocatalystshave hardly been explored. [33][34][35][36][37][38] Conjugated microporous polymers( CMPs) are an emerging class of porous organic materials, which have demonstrated a treasuret rove of applications.…”

Prospects of Emerging Engineered oxide nanomaterials and their Applications

“…This crystallographic structural phenomenon has been detected in TiO 2 , Al 2 O 3 , and VO 2 oxides. up to now, many phases of polymorphs of MON have been reported in literature, such as eight for TiO 2 (rutile, anatase, brokite, TiO 2 -B (bronze), TiO 2 -R (ramsdellite), TiO 2 -H (hollandite), TiO 2 -II (columbite) and TiO 2 -III (baddeyite)), seven for Al 2 O 3 (α → alpha; γ → gamma, δ → delta, θ → theta, ι → iota, κ → kappa and σ → sigma) and nine for VO 2 (rutile (R), monoclinic (M), triclinic (T), tetragonal (A), monoclinic (B), tetragonal (C), monoclinic (D), VO 2 with a BCC structure and paramontroseite VO 2 ) [63][64][65][66][67][68][69][70][71][72][73][74][75][76][77][78][79][80][81] .…”