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Electrochemical dual-pulse plating with sequential galvanostatic and potentiostatic pulses has been used to fabricate an electrocatalytically active Ni/Ni(OH) 2 /graphite electrode. This electrode design strategy to generate the Ni/Ni(OH) 2 interface on graphite from Ni deposits is promising for electrochemical applications and has been used by us for hydrogen generation. The synergetic effect of nickel, colloidal nickel hydroxide islands, and the enhanced surface area of the graphite substrate facilitating HO-H cleavage followed by H(ad) recombination, results in the high current density [200 mA/cm 2 at an overpotential of 0.3 V comparable to platinum (0.44 V)]. The easy method of fabrication of the electrode, which is also inexpensive, prompts us to explore its use in fabrication of solar-driven electrolysis.hydrogen evolution reaction | dual-pulse plating | nickel/nickel hydroxide interface | graphite rod electrode T o render electrochemical generation of H 2 from water ecofriendly, we could use electricity from solar photovoltaic devices. A major limitation would still be the use of Pt as the catalyst. In the last few years, there has been great interest in replacing Pt by inexpensive, readily available catalysts. Several catalysts have been studied in recent times for the electrochemical hydrogen evolution reaction (HER) including transition metal-based heterostructures (1-6) and certain metal-free catalysts (7-11). Of these, Ni-based catalysts such as Ni 2 P (12, 13), NiFeP (14), NiFe layered double hydroxide (15-17), and Ni/ NiO/carbon nanotube (18) seem to be more promising for water splitting. It has been shown recently that activation of a Nicarbon-based catalyst through the application of an electrochemical potential results in HER activity comparable to Pt in acidic medium (6). We have been investigating the use of Ni along with Ni(OH) 2 as a potential catalyst for the purpose, since Ni(OH) 2 clusters with Pt and other transition metals (19-23) generally exhibit good HER activity and Ni itself is only next to Pt in activity. With this purpose, we have used the dualpulse-plating (PP) method (24) to generate the Ni/Ni(OH) 2 interface embedded in graphene sheets on a graphite electrode. Amazingly, the Ni/Ni(OH) 2 /graphite electrode prepared by us gives a current density of ∼200 mA/cm 2 [at −0.30 V vs. reversible hydrogen electrode (RHE)] and an overpotential of ∼190 mV required to sustain a current density of 20 mA/cm 2 over long periods. For a current density of 200 mA/cm 2 , this electrode beats the activity of the Pt wire by a factor of ∼1.5 in terms of the overpotential.The outstanding performance of the Ni/Ni(OH) 2 /graphite electrode is due to the dual-PP method adopted by us to give rise to colloidal hydroxide inclusions in the electrodeposits (25-30) (Methods). While fabricating the Ni/Ni(OH) 2 interface, the galvanostatic pulses shift the cathodic potential in the negative direction to such an extent that the ensuing water splitting yielding hydrogen is followed by the simultaneous incorporati...

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