Partially reduced Ni²⁺, Fe³⁺-layered double hydroxide for ethanol electrocatalysis

Direct alcohol fuel cells can directly convert the chemical energy stored in small liquid alcohol molecules into electricity. The non-noble metal oxides and oxyhydroxides have poor electric conductivity, limiting their electrochemical performance. Herein, Ni₃Fe/NiFe(OH)_x heterostructure with Ni₃Fe alloy nanoparticles confined in amorphous NiFe(OH)_x matrix is facilely fabricated by partial reduction of Ni²⁺, Fe³⁺-layered double hydroxide (NiFe-LDH) precursor in flowing hydrogen. Small Ni₃Fe particles with about 4 nm diameter are clearly recognized after reduction at 250 °C. Further raising the reduction temperature to 350 °C results in a greater degree of segregation of Ni₃Fe each other. Moreover, the 350 °C reduction causes the formation of NiFeOx, accompanied by vanishment of the NiFe(OH)_x. Ethanol electrooxidation is carried out for evaluating the electrocatalytic performance of these samples. The electrocatalytic activity of NiFe-LDH precursor is enhanced by controlling H₂ reduction at 250 °C. The high electrical conductivity, created by Ni₃Fe metal alloy, is proposed to result in the high electrocatalytic activity of the Ni₃Fe/Ni₃Fe(OH)_x heterostructure.