Explain the commercial production of $Dihydrogen$.

(N/A) $(i)$ Electrolysis of acidified water using platinum electrodes gives hydrogen.
$2 H_{2}O_{(l)} \stackrel{\text{Electrolysis}}{\text{Traces of acid/base}} 2 H_{2(g)} + O_{2(g)}$
$(ii)$ High purity $(> 99.95 \%)$ dihydrogen is obtained by electrolysing warm aqueous barium hydroxide solution between nickel electrodes.
$(iii)$ It is obtained as a byproduct in the manufacture of sodium hydroxide and chlorine by the electrolysis of brine solution. During electrolysis,the reactions that take place are:
At anode: $2 Cl_{(aq)}^{-} \longrightarrow Cl_{2(g)} + 2 e^{-}$
At cathode: $2 H_{2}O_{(l)} + 2 e^{-} \longrightarrow H_{2(g)} + 2 OH_{(aq)}^{-}$
The overall reaction is:
$2 Na_{(aq)}^{+} + 2 Cl_{(aq)}^{-} + 2 H_{2}O_{(l)}$ $\longrightarrow Cl_{2(g)} + H_{2(g)} + 2 Na_{(aq)}^{+} + 2 OH_{(aq)}^{-}$
$(iv)$ Reaction of steam on hydrocarbons or coke at high temperatures in the presence of a catalyst yields hydrogen.
$C_{n}H_{2n+2} + n H_{2}O \stackrel{1270 \ K, Ni}{\longrightarrow} nCO + (2n+1) H_{2}$
e.g.,$CH_{4(g)} + H_{2}O_{(g)} \stackrel{1270 \ K, Ni}{\longrightarrow} \underbrace{CO_{(g)} + 3 H_{2(g)}}_{\text{water gas}}$
The mixture of $CO$ and $H_{2}$ is called water gas. As this mixture is used for the synthesis of methanol and a number of hydrocarbons,it is also called synthesis gas or 'syngas'. Nowadays,'syngas' is produced from sewage,saw-dust,scrap wood,newspapers,etc. The process of producing 'syngas' from coal is called 'coal gasification'.
$C_{(s)} + H_{2}O_{(g)} \stackrel{1270 \ K}{\longrightarrow} CO_{(g)} + H_{2(g)}$