We have prepared a graphitic carbon nitride (g-C 3 N 4 ) composite with MoO 3decorated Co 3 O 4 nanorods (Co 3 O 4 /MoO 3 /g-C 3 N 4 ) via the hydrothermal approach, and this hybrid material acts as a highly active and durable electrocatalyst for water splitting reactions. This material could fundamentally influence the catalytic processes and performance of oxygen evolution reaction (OER) and hydrogen evolution reaction (HER). The OER and HER activities of Co 3 O 4 -/MoO 3 -based nanorods are enhanced by blending with conducting support, for example, graphitic carbon nitrides (g-C 3 N 4 ). The X-ray diffraction pattern and the attenuated total reflectance-Fourier transform infrared data revealed that the as-synthesized nanorods are highly crystalline in nature and are attached to the g-C 3 N 4 support. Transmission electron microscopy, X-ray photoelectron spectroscopy, and Raman spectroscopy studies also affirm the successful heterointerface formation between Co 3 O 4 /MoO 3 nanorods and g-C 3 N 4 . This Co 3 O 4 /MoO 3 /g-C 3 N 4 rodshaped catalyst is highly stable in comparison to its individual constituent and generates a current density of 10 mA cm −2 at a low overpotential of 206 mV for OER and 125 mV for HER in alkaline and acidic media, respectively. This work could pave the way for developing Co 3 O 4 /MoO 3 /g-C 3 N 4 composite materials as electrocatalysts for overall water splitting reactions. KEYWORDS: Co 3 O 4 /MoO 3 /g-C 3 N 4 , decorated, nanorods, composite, water splitting, OER, HER

Development of economical and high-performance electrocatalysts for the oxygen evolution reaction (OER) is of tremendous interest for future applications as sustainable energy materials. Here, a unique member of efficient OER electrocatalysts has been developed based upon structurally versatile dumbbell-shaped ternary transition-metal (Cu, Ni, Co) phosphates with a three-dimensional (3D) (Cu2(OH)­(PO4)/Ni3(PO4)2·8H2O/Co3(PO4)2·8H2O) (CNCP) structure. This structure is prepared using a simple aqueous stepwise addition of metal ion source approach. Various structural investigations demonstrate highly crystalline nature of the composite structure. Apart from the unique structural aspect, it is important that the CNCP composite structure has proved to be an excellent electrocatalyst for OER performance in comparison with its binary or constituent phosphate under alkaline and neutral conditions. Notably, the CNCP electrocatalyst displays a much lower overpotential of 224 mV at a current density of 10 mA cm–2 and a lower Tafel slope of 53 mV dec–1 with high stability in alkaline medium. In addition, X-ray photoelectron spectroscopy analysis suggested that the activity and long-term durability for the OER of the ternary 3D metal phosphate are due to the presence of electrochemically dynamic constituents such as Ni and Co and their resulting synergistic effects, which was further supported by theoretical studies. Theoretical calculations also reveal that the incredible OER execution was ascribed to the electron redistribution set off in the presence of Ni and Cu and the most favorable interaction between the *OOH intermediate and the active sites of CNCP. This work may attract the attention of researchers to construct efficient 3D ternary metal phosphate catalysts for various applications in the field of electrochemistry.

Among the accessible techniques, the production of hydrogen by electrocatalytic water oxidation is the most established process, which comprises oxygen evolution reaction (OER) and hydrogen evolution reaction (HER).

The importance of protein−nanoparticle (NP) conjugates for biomedical applications has seen an exponential growth in the past few years. The protein corona formation on NPs with human serum albumin (HSA), being the most abundant protein in blood serum, has become one of the most studied protein analyses under NP−protein interactions as HSA is readily adsorbed on the surface of the NPs. Understanding the fate of the NPs in physiological media along with the change in biological responses due to the formation of the protein corona thus becomes important. We analyzed the HSA protein corona formation on gold nanorods (AuNRs) through different spectroscopic studies in addition to the effects of change in the protein concentration on the protein−NP interactions. Different imaging techniques such as high-resolution transmission electron microscopy, field emission scanning electron microscopy, and atomic force microscopy were used to determine the morphology and the dimensions of the nanorods and the protein−nanorod conjugates. Fourier-transform infrared data showed a reduction in the α-helix content and an increase in β-sheet content for the HSA−AuNR conjugate compared to the native protein. A decrease in steady-state fluorescence intensity occurred with instant addition of AuNR to HSA showing better and efficient quenching of Trp fluorescence for the lower concentration of protein. Time-correlated single photon counting results showed greater energy transfer efficiency and faster decay rate for higher concentrations of proteins. The circular dichroism study gives insight into the secondary structural changes due to unfolding, and a greater change was observed for lower concentrations of protein due to a thermodynamically stable protein corona formation. Surface-enhanced Raman spectroscopy (SERS) indicated the presence of aromatic residues such as Phe, Tyr, and Cys that appear to be close to the surface of the AuNRs in addition to hydrophobic interactions between AuNR and the protein. The disordered and flexible regions mapped onto HSA (PDB: 1AO6), predicted by the intrinsically disordered region predictors, point toward the interactions of similar residues with the nanorods observed from SERS and fluorescence studies. These studies could provide a clearer understanding of the interactions between HSA and AuNRs for possible biological applications.

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