a metallic nanostructure, the metal of which is selected from the group of Cu, Zn, Ni, Fe, and Ag or mixtures thereof, said metallic nanostructure being part of a metallic hierarchical structure containing both micro and nanostructuration, said metallic hierarchical structure being of the same metal as defined above,

a hydrophobic layer of compounds covering the surface of said metallic hierarchical structure, said compounds being chemisorbed to said surface,

said metallic hierarchical structure being porous,

said compounds being chosen from the group of:

a compound of Formula 1,

wherein,

A represents,

SH,

—P(O)(OH)2,

—CO2H,

—SeH,

—TeH,

—Si(OH)3,

Six3, wherein X represents a halogen,

an acetylacetone group having the structure of Formula 2,

R is chosen from the groups of,

(C5-C100)-alkyl linear or branched,

(C5-C100)-alkenyl linear or branched,

(C5-C100)-alkynyl linear or branched,

(C5-C100)-heteroralkyl linear or branched,

(C5-C100)-heteroalkenyl linear or branched,

(C5-C100)-heteroalkynyl linear or branched,

said alkyl, alkenyl, alkynyl, heteroalkyl, heteroalkenyl and heteroalkynyl can be further substituted by one or more groups selected from:

amines,

—ORa, wherein Ra represents a hydrogen atom, a (C1-C20)-alkyl group, a (C1-C10)-alkyl group, or a (C1-C5)-alkyl group,

halogen,

aryl,

—CO2Rb, wherein Rb represents a hydrogen atom, a (C1-C20)-alkyl group, a (C1-C10)-alkyl group, or a (C1-C5)-alkyl group,

—CX3 groups, wherein X represents a halogen,

a compound of Formula 3,

wherein,

A represents Se or S,

R is a group as defined above,

polysiloxane compounds chosen from the groups of (C1-C100)-polyalkylsiloxane, or polyarylsiloxane, said polyalkylsiloxane and polyarylsiloxane can be further substituted by one or more groups selected from:

amines,

—ORa, wherein Ra represents a hydrogen atom, a (C1-C20)-alkyl group, a (C1-C10)-alkyl group, or a (C1-C5)-alkyl group,

halogen, wherein X represents a halogen,

—CO2Ra, wherein Ra represents a hydrogen atom, a (C1-C20)-alkyl group, a (C1-C10)-alkyl group, or a (C1-C5)-alkyl group,

said electrode having a hydrophobicity as determined by contact angle measurement from 130° to 175°,

said electrode having an electrochemically active surface area (EASA) lower than 10% of the geometric surface area of said metallic hierarchical structure,

wherein regions of the electrochemically active surface area are located at extremities of said metallic hierarchical structure, and

wherein the electrochemically active surface area is exposed to an electrolyte solution.