= Solution
Gas formation is decided by each interfacial <electrode potential> and reaction kinetics, rather than by comparing the terminal cell <voltage> directly with 1.23 V. On the conditional model above, the <cathode> potential is $E_c\simeq0.34-0.12854=+0.21146$ V versus the <standard hydrogen electrode>. At unit proton activity and unit hydrogen <pressure> this is above the hydrogen equilibrium potential, so hydrogen evolution is not favored there. The <anode> is at $E_a\simeq1.0188$ V, below the unit-activity <oxygen> equilibrium potential of 1.23 V, so <oxygen> evolution is likewise not favored at the intended point. \b[Neither gas is expected in that model, despite a terminal <voltage> near 2 V; 1.2 V is lost in the <electrolyte>.]
Without the missing cathodic kinetic information, the exact <cathode> potential is not fixed, so the hydrogen conclusion is conditional. Locally depleted <copper> <ions>, increased current, <electrode> blocking or strong <passivation> can move an interface into gas evolution. Actual proton/<oxygen>/hydrogen activities shift equilibrium through the <Nernst equation>, and gas <nucleation> and activation barriers further affect observable bubbles. A reference <electrode> at each interface and direct gas observation distinguish these effects from an increased solution-resistance drop.
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