Pt/flaky graphite–NiO composite electrocatalyst for the alkaline hydrogen evolution reaction

For the first time, a novel kind of alkaline hydrogen evolution reaction (HER) catalyst, namely, a flaky graphite (denoted as FG) and nickelous oxide (NiO) composite material supported platinum (Pt) catalyst (denoted as Pt/FG-NiO), is prepared via an air calcination-assisted hydrothermal method, in which the commercial graphite, one kind of nickel-containing substance (nickel acetate tetrahydrate (Ni(CH 3 COO) 2 ·4 H 2 O) or nickel acetylacetonate (C 10 H 14 NiO 4 ) or nickel oxalate dehydrate (NiC 2 O 4 ·2 H 2 O)) and chloroplatinic acid hexahydrate (H 2 PtCl 6 ·6 H 2 O) are utilized as the starting materials. In this work, firstly, three precursors are synthesized through calcining the mixture having the commercial graphite and one kind of nickel-containing substance in air at 550℃ for 1 h, namely, precursor p 1 , p 2 and p 3 are respectively prepared using Ni(CH 3 COO) 2 ·4 H 2 O, C 10 H 14 NiO 4 and NiC 2 O 4 ·2 H 2 O. Subsequently, the resulting precursor p 1 , p 2 and p 3 are subjected to the hydrothermal treatment in the presence of chloroplatinic acid solution, respectively, generating catalyst c 1 , c 2 and c 3 . As demonstrated by XRD and XPS results, graphite, NiO and metallic Pt are the major substances of all fabricated catalysts. More importantly, all prepared catalysts, especially catalyst c 1 , showed an excellent electrocatalytic activity towards alkaline HER. For example, the overpotential value to attain a HER current density of 10 mA cm −2 on catalyst c 1 is as lower as 39.6 mV, being rather lower than that of catalyst c 2 (52.2 mV) and c 3 (57.2 mV). To be noted, the value of 39.6 mV for catalyst c 1 is very close to that of the commercial platinum/carbon (Pt/C) catalyst (37.9 mV). The Tafel slope values of catalyst c 1 , c 2 , c 3 and Pt/C for HER are about 41.3, 52.4, 59.0 and 49.5 mV dec −1 , respectively. In the chronoamperometry (CA) test, the HER current density measured on catalyst c 1 is about 7.81 mA cm −2 after 10 h, being much higher than that of catalyst c 2 (2.15 mA cm −2 ), c 3 (2.73 mA cm −2 ) and the commercial Pt/C (5.63 mA cm −2 ). After a thorough characterization, the greatly decreased R ct and the larger ECSA value are analyzed to be the main reasons giving catalyst c 1 an outstanding HER electrocatalytic activity. Showing the preparation of a novel HER catalyst of Pt/FG-NiO as well as its satisfied HER electrocatalytic performance are the main contributions of the present work, which is very beneficial to the development of Ni and Pt based alkaline HER catalyst.