Semiconductor-mediated photoelectrochemical (PEC) water splitting to generate hydrogen and oxygen has gained tremendous attention as it has the capability to overcome the world energy crisis. However, limited solar light absorption and a high charge carrier recombination rate are major bottlenecks in achieving the desired efficiency of PEC devices. Fabrication of semiconductor−metal/metal oxide heterostructure holds a great promise to overcome these bottlenecks as it facilitates solar light absorption, separation, and transport of charge carriers. To this end, we demonstrate a fabrication methodology to design stable tailored heterostructures via click chemistry. To test the proposed methodology, we choose gold (Au), rutile-TiO 2 (R-TiO 2 ), and anatase TiO 2 (A-TiO 2 ) as model system and designed tailored triad heterostructure, i.e.,

The activity of electrocatalysts critically depends on the chemical coordination around the active sites. Amorphous materials have short‐range atomic ordering while their crystalline counterparts have both short and long‐range ordering. Traditional synthesis of amorphous materials, involving quenching from high temperatures is unsuitable as it results in less porosity and surface area. In this context, room‐temperature syntheses of high surface area amorphous materials with high activity are desirable. Here, we contrast two electrochemical synthesis procedures for generating high surface area amorphous Co3O4 at room temperature via electrochemical ion intercalation/deintercalation and surface oxidation/reduction cycles and evaluate their performance for electrocatalytic oxygen evolution reaction (OER). In the first approach, Li‐ion is used for the intercalation/deintercalation (Li/D−Li) cycles in Co3O4, which leads to expansion and contraction of structure, inducing amorphization of Co3O4 by the pulverization of crystal structure in non‐aqueous medium. In the second approach, rapid electrochemical surface oxidation/reduction (Ox/Red) of Co3O4 in the aqueous medium leads to the formation of a metastable amorphous structure. The OER specific activity (activity per unit electrochemical surface area) for Li/D−Li−Co3O4 is ∼3.5 times and Ox/Red‐ Co3O4 induced amorphization is ∼2.5 times higher than their crystalline Co3O4. The superior OER metrics of both the room‐temperature amorphization techniques are rationalized via the increase in the ratio of Co2+/Co3+ obtained from the Co‐2p XPS spectra. Further, the decrease in overall polarization resistance per site for the OER reaction for both amorphous samples were analyzed from the Tafel plot and electrochemical impedance spectroscopy (EIS). In Li/D−Li−Co3O4, the Li‐ion intercalation in bulk Co3O4 structure generates higher bulk‐oxygen vacancies leading to higher conductivity and reduction in overall charge‐transport resistance for electrocatalyst. On the other hand, Ox/Red‐ induced amorphization is restricted to the surface or near‐surface only with the formation of a small amount of metallic Co which hampers the OER.

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We modulate electron-hole separation at semiconductor junctions by stabilization of 'non-native' structures which are nanostructures whose discrete translational symmetry is different from that of the crystalline ground state. Four materials synthesis strategies involving click and colloidal chemistry are discussed and these methods can be potentially generalized to design a range of isomaterial and heteromaterial heterojunctions. The dynamics of electron-hole separation is demonstrated using density functional theory (DFT) which can be experimentally studied also using electrochemical impedance and photolumiscence spectroscopy.

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