Ruthenium-Cobalt Nanoalloy Embedded within Hollow Carbon Spheres as a Bifunctionally Robust Catalyst for Hydrogen Generation from Water Splitting and Ammonia Borane Hydrolysis

Developing high-efficiency and low-cost catalysts for the hydrogen evolution reaction (HER) and hydrogen generation from chemical hydrogen storage materials are both significant and critical for the exploitation and utilization of hydrogen energy. Herein, we reported a ruthenium cobalt alloy (Ru, 1.8 wt %) enriched in hollow carbon spheres (denoted RuCo@HCSs) synthesized through a wet vacuum impregnation method followed by pyrolysis treatment. RuCo alloys are obtained by direct reduction of Ru and Co chloride precursors, avoiding hydrothermal and washing processes, and the Ru/Co ratio of the alloy can be precisely controlled. The RuCo@HCS catalyst not only displays outstanding HER performance with a low overpotential (eta(10)) and Tafel slope (21 mV and 32 mV dec(-1) in 1.0 M KOH, 57 mV and 48 mV dec(-1) in 0.5 M H2SO4, and 49 mV and 59 mV dec(-1) in 1.0 M phosphate-buffered saline) within a wide pH range but also offers a high turnover frequency (TOF) value of 784 mol(H2) min(-1) mol(cat)(-1) for the hydrolysis of ammonia borane under ambient conditions. The excellent catalytic performance of RuCo@HCSs is attributed to the special hollow embedded configuration and collaborative effect between carbon shells and RuCo alloys. Density functional theory calculations reveal that the excellent catalytic performance of RuCo@HCSs originates from the carbon shells activated by the electron transferred from the embedded metal nanoparticles. This work provides a convenient route for preparing highly active and inexpensive metal/carbon composite bifunctional catalysts.