Different metal chalcogenides, being a potential candidate for hydrogen evolution catalysts, have attracted enormous attention in the field of water splitting. In the present study, AgS/Ag is revealed as an efficient catalyst for hydrogen evolution. When a sacrificial template of the CuS nanostructure is used, AgS/Ag heterostructures are synthesized following a simple wet-chemical technique. Two different routes, wet chemical and hydrothermal, are followed to modulate the morphology of the CuS templates from flower ball to wirelike structures, which subsequently results in the formation of AgS nanostructure. Finally, the Ag layer is deposited on AgS with the help of a photoreduction technique. The unique heterostructure of AgS/Ag shows efficient catalytic activity in the H evolution reaction. A AgS/Ag wire can successfully generate a 10 mA/cm current density at a -0.199 V potential. AgS/Ag contains the micronanostructure where nanoplates of AgS/Ag assemble to give rise to microstructures such as flower balls and wire.

Development of a stable catalyst that can efficiently function for longer time for energy conversion process in water splitting is a challenging work. Here, NiCo 2 O 4 /NiO nanosheets are successfully synthesized following a simple wet-chemical route, followed by the combustion technique. Finally, the synthesized catalyst NiCo 2 O 4 /NiO can function as an efficient catalyst for oxygen evolution reaction. Nanosheets with interconnections are very useful for better electron transportation because the pores in between the sheets are useful for the diffusion of electrolyte in electrocatalysis. In oxygen evolution reaction, these sheets can generate current densities of 10 and 20 mA/cm 2 , respectively, upon application of 1.59 and 1.62 V potential versus reversible hydrogen electrode (RHE) under alkaline condition. In contrast, bare NiCo 2 O 4 nanowire bundles can generate a current density of 10 mA/cm 2 upon application of 1.66 V versus RHE. The presence of NiO in NiCo 2 O 4 /NiO nanosheets helps to increase the conductivity, which further increases the electrocatalytic activity of NiCo 2 O 4 /NiO nanosheets.

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Designing metal hydroxide electrocatalysts with high efficiency to overcome the slow reaction kinetics of the oxygen evolution reaction (OER) is considered as a significant approach for renewable energy resources. We report here a simple methodology to synthesize 2D thin nickel hydroxide/nickel oxyhydroxide sheets that show efficient activity towards OER. Further, by doping with a heteroatom, Fe, thinner sheets of nickel hydroxide/nickel oxyhydroxide are developed, which exhibit enhanced electrocatalytic activity towards OER with high durability. Fe‐doped Ni(OH)2/NiOOH requires only 200 mV overpotential to produce 10 mA/cm2, whereas bare Ni(OH)2/NiOOH needs 290 mV overpotential. Moreover, Fe‐doped nickel hydroxide/nickel oxyhydroxide shows a minimal Tafel value of 48 mV/decade, which is even lower than RuO2/CC (82 mV/decade). X‐ray photoelectron spectroscopy indicates that in the case of Fe‐doped Ni(OH)2/NiOOH, the Ni3+ signal enhances, which indicates the favourable stabilization of Ni3+ in the presence of Fe3+ dopant. Under electrochemical OER conditions, in Fe‐doped Ni(OH)2/NiOOH, Fe3+ species help to generate more Ni3+, which function as the active species. Fe0.06Ni0.94(OH)2/NiOOH shows long‐term stability for at least 24 hours in alkaline medium. This work unveils a green strategy for Fe‐doping in 2D thin sheets of Ni(OH)2/NiOOH, which show improved electrocatalytic activity compared to bare Ni(OH)2/NiOOH. The mechanism of OER activity enhancement after Fe‐doping is proposed here.

The efficient utilization of solar power is becoming an important strategy for its conversion into a storable, clean, and renewable energy source like H 2 . To generate H 2 as a chemical fuel from solar power, attempts are being made to establish photoelectrochemical (PEC) water splitting as an efficient, greener pathway. Here, the surfaces of ZnO 2D nanosheets are adorned by graphite-like carbon nitride (g-C 3 N 4 ) quantum dots (QDs) with the intention of developing efficient photoanodes. Sensitization of ZnO nanosheets with C 3 N 4 QDs leads to a more enhanced PEC performance than that of bare ZnO. The observed enhancement in PEC is due to the high light absorbance and photon-generated charge-carrier separation. The best-obtained ZnO/C 3 N 4 photoanode exhibits a nearly 2.29 times as high photocurrent density compared to bare ZnO. ZnO 2D sheets can generate a photocurrent density of 0.414 mA cm −2 at 0.5994 V versus reversible hydrogen electrode (RHE), whereas ZnO/C 3 N 4 can produce 0.952 mA cm −2 at 0.5994 V versus RHE under uninterrupted conditions of light illumination. Further, there is improvement in the observed PEC activity of the heterostructure because of enhancement in the carrier density. The carrier density enhances nearly 2.2 times in the heterostructure compared to the bare ZnO sheet. ZnO/C 3 N 4 shows a maximum photoconversion efficiency (η) of 0.70%. Both ZnO 2D sheets and the ZnO/C 3 N 4 heterostructure show efficient stability under chopped irradiation of light for 1000 s. The stability of ZnO/C 3 N 4 is also determined for 1 h under continuous illumination.