Recent advances in titanium carbide MXene-based nanotextures with influential effect of synthesis parameters for solar CO_(2)reduction and H_(2)production:A critical review

Photocatalytic solar to energy conversion is considered an attractive approach for overcoming energy crises and environmental concerns.Recently,titanium carbide(Ti_(3)C_(2))MXenes have been recognized as promising cocatalysts based on their metallic conductivity,excessive active reaction sites,and enlarged surface area.The current review focuses on the properties and applications of Ti_(3)C_(2)MXenes useful in the field of photocatalysis.More specifically,surface modification of Ti_(3)C_(2)MXenes by varying synthesis parameters to get pure materials and also composites with the role of functional groups towards solar energy conversion applications is highlighted in this review.The effect of etching and oxidizing pathways to get an efficient cocatalyst has been discussed in detail.Considering the significant effect of parameters,optimum synthesis conditions such as etchant type,concentration,time and type of intercalant in both the Ti_(3)C_(2)synthesis approaches for improved photoactivity are discussed.Additionally,the surface modification of Ti_(3)C_(2)through oxidation for TiO2growth on its surface is deliberated with a detailed discussion on etchant type,concentration,etching time,and environmental factors.The optimum oxidation condition,including temperature,time,and environment for thermal treatment of Ti_(3)C_(2),were also included.Lastly,the review summarizes the conclusion and future perspectives for solar energy conversion applications.

Constructing S-scheme 2D/0D g-C_(3)N_(4)/TiO_(2) NPs/MPs heterojunction with 2D-Ti3AlC2 MAX cocatalyst for photocatalytic CO_(2) reduction to CO/CH_(4) in fixed-bed and monolith photoreactors

Exfoliated 2D MAX Ti_(3) AlC_(2) conductive cocatalyst anchored with g-C_(3)N_(4)/TiO_(2) to construct 2D/0D/2D het-erojunction has been explored for enhanced CO_(2) photoreduction in a fixed-bed and monolith photoreac-tor.The TiO_(2) particle sizes(NPs and MPs)were systematically investigated to determine effective metal-support interaction with faster charge carrier separation among the composite materials.When TiO_(2) NPs were anchored with 2D Ti_(3) AlC_(2) MAX structure,10.44 folds higher CH_(4) production was observed com-pared to anchoring TiO_(2) MPs.Maximum CH_(4) yield rate of 2103.5μmol g^(−1) h^(−1) achieved at selectivity 96.59%using ternary g-C_(3)N_(4)/TiO_(2)/Ti_(3) AlC_(2)2D/0D/2D composite which is 2.73 and 7.45 folds higher than using binary g-C_(3)N_(4)/Ti_(3) AlC_(2) MAX and TiO_(2) NPs/Ti_(3)AlC_(2) samples,respectively.A step-scheme(S-scheme)photocatalytic mechanism operates in this composite,suppressed the recombination of useful electron and holes and provides higher reduction potential for efficient CO_(2) conversion to CO and CH_(4).More im-portantly,when light intensity was increased by 5 folds,CH_(4) production rate was increased by 3.59 folds under visible light.The performance of composite catalyst was further investigated in a fixed-bed and monolith photoreactor and found monolithic support increased CO production by 2.64 folds,whereas,53.99 times lower CH_(4) production was noticed.The lower photocatalytic activity in a monolith photore-actor was due to lower visible light penetration into the microchannels.Thus,2D MAX Ti_(3) AlC_(2) composite catalyst can be constructed for selective photocatalytic CO_(2) methanation under visible light in a fixed-bed photoreactor.